CompTIA A+ Core 1 (220-1201) · glossary

A+ Core 1 glossary

540 terms you need for CompTIA A+ Core 1 (220-1201), in plain words. Each one links to the lesson that teaches it. The acronym list is further down.

#A B C D E F G H I J K L M N O P Q R S T U V W Acronyms

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2.4 GHz: 2.4 GHz: longest range, best through walls, but crowded (Bluetooth, microwaves) and only 3 non-overlapping 20 MHz channels. Lesson: The three Wi-Fi bands
3G: 3G is old and being shut down by most carriers. Lesson: Cellular data: 3G, 4G, 5G
4G (LTE): 4G (LTE) is the common baseline. Lesson: Cellular data: 3G, 4G, 5G
5 GHz: 5 GHz: many more channels, faster, shorter range. Lesson: The three Wi-Fi bands
5G: 5G adds much more speed and lower latency: low-band (wide coverage), sub-6 GHz/mid-band, and mmWave (very fast, very short range, blocked by walls). Lesson: Cellular data: 3G, 4G, 5G
6 GHz: 6 GHz (Wi-Fi 6E and Wi-Fi 7): a huge clean band with lots of wide channels, shortest range, and only newer devices can use it. Lesson: The three Wi-Fi bands
20+4 pin: The main 20+4 pin connector fits modern 24-pin boards, and the 4 pins detach for older 20-pin boards. Lesson: 20+4 pin connector, modular and redundant PSUs
24-pin ATX: Power connectors on the board: 24-pin ATX main power and 4/8-pin ATX12V (EPS) CPU power near the socket. Lesson: Power connectors and headers
66 block: A punchdown block is where wires terminate in a closet or patch panel: 66 blocks (older phone) and 110 blocks (data, Cat 5e and up). Lesson: Copper network connectors
80 PLUS: Energy efficiency is shown by the 80 PLUS rating: an efficient PSU wastes less power as heat. Lesson: Wattage and energy efficiency
110 block: A punchdown block is where wires terminate in a closet or patch panel: 66 blocks (older phone) and 110 blocks (data, Cat 5e and up). Lesson: Copper network connectors
A
AAA: AAA (authentication, authorization, accounting): one server checks who you are, what you may do and logs what you did, e.g. Lesson: Core server roles
AAAA: AAAA maps a name to an IPv6 address. Lesson: DNS record types
Access point (AP): An access point (AP) connects wireless clients to the wired network (it bridges Wi-Fi to Ethernet). Lesson: Router, switch, access point
Active converter: HDMI to VGA) needs an active converter with a chip, not a simple adapter. Lesson: Adapters
Adapters: Adapters convert one connector or signal to another: USB-C to HDMI, DisplayPort to HDMI, DVI-to-HDMI (both digital, passive), USB-to-Ethernet, USB-to-serial, Lightning to 3.5 mm. Lesson: Adapters
ADF: The ADF (automatic document feeder) pulls a stack of pages through by itself; a duplexing ADF scans both sides. Lesson: ADF and flatbed scanner
amber/red = fault or predicted failure: Server drive bays and RAID controllers use LED status indicators: green/blinking = activity, amber/red = fault or predicted failure, blinking amber = rebuild or locate. Lesson: LED status indicators and audible alarms
AMD: AMD used PGA for AM4 (pins on the CPU) and moved to LGA with AM5. Lesson: CPU sockets and compatibility
AMD-V (SVM): Running VMs well needs CPU hardware virtualization enabled in firmware: Intel VT-x or AMD-V (SVM), plus SLAT (EPT/RVI). Lesson: Virtualization support
Antenna leads: The card connects to antenna leads; it has no antenna of its own. Lesson: Wireless cards
APIPA: If a device is set for DHCP but no DHCP server answers, Windows assigns itself an APIPA address: 169.254.x.x with mask 255.255.0.0, and no gateway. Lesson: APIPA
APIPA 169.254.x.x: Limited connectivity (no internet, local only): usually an APIPA 169.254.x.x address from a failed DHCP request, a wrong gateway, or a VLAN issue. Lesson: Limited connectivity
Application crashes: Application crashes across many apps suggest bad RAM or overheating; one app crashing suggests that app or its driver. Lesson: Sluggish performance and application crashes
Application virtualization: Application virtualization: a single app is packaged or streamed from a server and runs isolated from the local OS with no normal install; VDI, by contrast, delivers a whole desktop. Lesson: Legacy, cross-platform and application virtualization
ARM: ARM is a RISC design: power-efficient, used in phones, tablets and a growing number of laptops; apps must be built for ARM or emulated. Lesson: CPU architecture and core configurations
Array missing: Array missing: the controller does not show the array: check controller health, cables/backplane, controller firmware/driver, and never initialize (that erases it). Lesson: RAID failure and array missing
ATX: ATX: 12 x 9.6 in (305 x 244 mm), up to 7 expansion slots. Lesson: Motherboard form factors
ATX12V (EPS): Power connectors on the board: 24-pin ATX main power and 4/8-pin ATX12V (EPS) CPU power near the socket. Lesson: Power connectors and headers
Audible alarm: The RAID controller or NAS may sound an audible alarm (continuous beeping) when an array is degraded. Lesson: LED status indicators and audible alarms
Audio issues: Audio issues over HDMI/DisplayPort: wrong playback device selected, muted monitor/TV, or a VGA/DVI link that carries no audio. Lesson: Color, dim image and audio
Audit logs: Audit logs record who printed, copied or scanned what and when. Lesson: Security
Authentication failures: Authentication failures: wrong Wi-Fi passphrase, an expired or changed domain password saved on the device, expired certificate on 802.1X/enterprise Wi-Fi, wrong date/time (breaks certificates), or a locked-out… Lesson: Authentication failures and intermittent internet
Auto-switching: Most PSUs are auto-switching (100-240 V). Lesson: Input voltage
Availability: Availability: the service stays up, through redundancy across zones/regions; given in the provider's SLA, e.g. Lesson: Elasticity and availability
B
B key: Keys: M key (PCIe x4/NVMe, and some SATA), B key (SATA or PCIe x2), B+M fits both (usually SATA). Lesson: SSD form factors: M.2 and mSATA
B+M: Keys: M key (PCIe x4/NVMe, and some SATA), B key (SATA or PCIe x2), B+M fits both (usually SATA). Lesson: SSD form factors: M.2 and mSATA
Backlight: An LCD uses liquid crystals that do not make light: a backlight shines through them. Lesson: LCD panel types: IPS, TN, VA
Backup: If more drives fail than the level allows (2 in RAID 5), the array fails and you restore from backup. Lesson: RAID failure and array missing
Badging: Badging: tap an ID badge at the MFD's reader to sign in. Lesson: Security
Between networks: A router forwards traffic between networks using IP addresses: it is the default gateway and does NAT at a SOHO. Lesson: Router, switch, access point
Biometrics: Biometrics: a fingerprint reader or an IR face camera lets users sign in with "something you are" (e.g. Lesson: Physical privacy and security components
BIOS: UEFI replaced legacy BIOS: mouse-driven menus, GPT disks over 2 TB, faster boot, Secure Boot. Lesson: BIOS vs. UEFI and boot options
BIOS (supervisor/admin) password: A BIOS (supervisor/admin) password is needed to change firmware settings. Lesson: Passwords, Secure Boot and TPM features
Blank screen: Blank screen with fans running: check monitor power and input, the cable, the GPU seating and power, then reseat RAM. Lesson: POST beeps and blank screen
Block-level: A SAN (storage area network) is a dedicated high-speed network that gives servers block-level access to shared storage (Fibre Channel or iSCSI). Lesson: Network types: MAN, WAN, SAN
Bluetooth: Bluetooth is a short-range PAN (about 10 m for common devices) for headsets, keyboards and speakers. Lesson: Wireless connection methods
Bluetooth Low Energy (BLE): Common devices reach about 10 m (Class 2); Bluetooth Low Energy (BLE) saves power for sensors, beacons and wearables. Lesson: Bluetooth
boot (user/power-on) password: A boot (user/power-on) password is needed to start the computer at all. Lesson: Passwords, Secure Boot and TPM features
Boot options: Boot options set the boot order (SSD, USB, network/PXE) and UEFI vs. Lesson: BIOS vs. UEFI and boot options
Boot order: Bootable device not found (or "no boot device", "operating system not found"): check simple things first: a USB stick or disc left in that boots first, boot order in UEFI, UEFI vs. Lesson: Bootable device not found
Bridged: Network: virtual switches; VMs can be bridged (on the real LAN), NAT (share the host IP), internal/host-only or isolated. Lesson: VM requirements: storage, network, security
Broken screen: A broken screen may crack only the glass, or the display and digitizer too. Lesson: Broken screen and digitizer issues
Burn-in: OLED pixels make their own light, so there is no backlight: perfect blacks, thin panels, but a risk of burn-in from static images. Lesson: OLED and mini-LED
Burning smell: Burning smell: power off and unplug at once. Lesson: No power and burning smell
Burnt-out bulb: Burnt-out bulb: lamp hours are finished, or the lamp LED is lit and no image. Lesson: Projector bulbs and shutdowns
BYOD: BYOD (bring your own device) phones are the user's; MDM manages only a work profile/container so IT can wipe work data, not personal photos. Lesson: Mobile device management (MDM)
C
Cable: Cable (DOCSIS over the TV coax): fast downloads, slower uploads, bandwidth shared with neighbors. Lesson: Fiber, cable and DSL
Cable lock: Add a privacy screen filter against shoulder surfing and a cable lock slot against theft. Lesson: Physical privacy and security components
Cable modem: A cable modem connects coax (F-type, DOCSIS) to Ethernet. Lesson: Cable modem, DSL modem, ONT
Cable stripper: A cable stripper removes the outer jacket without nicking the pairs. Lesson: Making a cable: stripper and crimper
Cable tester: A cable tester checks each wire: continuity, opens, shorts, miswires, split pairs (wiremap). Lesson: Testing: cable tester and loopback plug
Cabling issues: Then cabling issues: loose or damaged cable, wrong port (onboard vs. Lesson: Incorrect input source and cabling issues
Calendar: Phones sync mail, calendar and contacts with the company mail server (e.g. Lesson: Synchronization and data caps
Calibrate: Calibrate to align color and density. Lesson: Laser printers
Calibration: Clean the screen, update the OS/driver, and run the touch calibration tool (on Windows tablets: Tablet PC settings/Calibrate). Lesson: Cursor drift, calibration and stylus
Cannot install apps: Cannot install apps: not enough storage, OS version too old, app not compatible, store account/payment issue, or MDM policy blocks it. Lesson: Malware and cannot install apps
Capture card: Capture card: records video from cameras or consoles (HDMI in) for streaming and editing. Lesson: Expansion cards
CCFL: Older LCDs used a CCFL (fluorescent tube) backlight. Lesson: Backlights and the inverter
Cellular: Cellular (4G/5G): fast to set up, good as backup, may have data caps. Lesson: Satellite, cellular and WISP
Cellular location services: Cellular location services estimate position from nearby cell towers (and Wi-Fi networks): works indoors, less precise. Lesson: Location services
Channel width: Channel width trades speed for room: 20, 40, 80, 160 MHz, and 320 MHz with Wi-Fi 7 in 6 GHz. Lesson: Channels, widths and regulations
Channels: Each band is split into channels (center frequencies). Lesson: Channels, widths and regulations
Charge and pairing: Stylus not working: an active stylus needs charge and pairing (Bluetooth); check the tip, and confirm the device supports that stylus type. Lesson: Cursor drift, calibration and stylus
Chipset: The CPU must match the board's socket and chipset. Lesson: CPU sockets and compatibility
Clean: Clean with a toner vacuum (not a household vacuum) and isopropyl alcohol on rollers. Lesson: Laser printers
Clean printheads: Maintenance: clean printheads with the built-in utility (clogged nozzles leave lines/gaps), replace cartridges, calibrate (align the heads after a cartridge change), and clear jams by opening the access door and… Lesson: Inkjet printers
Clean the heating element: Maintenance: replace paper with the right type and side facing up, clean the heating element with isopropyl alcohol, and remove debris (label glue, dust) from the path. Lesson: Thermal printers
Clear jams: Maintenance: clean printheads with the built-in utility (clogged nozzles leave lines/gaps), replace cartridges, calibrate (align the heads after a cartridge change), and clear jams by opening the access door and… Lesson: Inkjet printers
Cleartext: FTP uses TCP 20 (data) and 21 (control); sends credentials in cleartext. Lesson: File transfer and remote access
Clicking sounds: Clicking sounds (the "click of death") usually mean the read/write head cannot find its track and keeps resetting. Lesson: Grinding and clicking
Client-to-site: Client-to-site (remote access): a laptop at home joins the office network. Lesson: VPN
Clogged nozzles: Lines down the printed pages (vertical streaks): on a laser, a scratched or dirty drum (imaging unit), dirty transfer roller, or debris on the fuser; on an inkjet, clogged nozzles (white lines/gaps) or a dirty… Lesson: Lines down the page
Cloud storage: through an Exchange-style account) and files with cloud storage. Lesson: Synchronization and data caps
CMOS battery: Inaccurate system date/time that resets after power-off means a dead CMOS battery (CR2032 coin cell). Lesson: Swollen capacitors and wrong date/time
CNAME: CNAME is an alias: a name that points to another name (shop.kibbleco.example to web1.kibbleco.example). Lesson: DNS record types
Coax: Coax has one center conductor, insulation, a braided shield and a jacket. Lesson: Coaxial
Color gamut: Color gamut is the range of colors shown, given as % of sRGB, DCI-P3 or Adobe RGB. Lesson: Display attributes
Community: Community: shared by several organizations with common needs (e.g. Lesson: Deployment models
Configuration page: Print a configuration page for its IP. Lesson: Connectivity issues
Connection-oriented: TCP is connection-oriented: three-way handshake (SYN, SYN-ACK, ACK), sequencing, acknowledgments and retransmission. Lesson: TCP vs. UDP
Connectionless: UDP is connectionless: no handshake, no acknowledgments, no resend. Lesson: TCP vs. UDP
Connectivity issues: Connectivity issues: printer offline or unreachable. Lesson: Connectivity issues
Contacts: Phones sync mail, calendar and contacts with the company mail server (e.g. Lesson: Synchronization and data caps
Container: A container packages an app with its libraries and settings, but shares the host OS kernel. Lesson: Containers
Copies: Also check the scanner glass/ADF strip if lines appear only on copies. Lesson: Lines down the page
Core configurations: Core configurations: multicore (several cores per CPU), hyper-threading/SMT (2 threads per core), and hybrid designs with performance and efficiency cores. Lesson: CPU architecture and core configurations
Corporate applications: Corporate applications are pushed from the MDM app catalog. Lesson: Mobile device management (MDM)
Corporate-owned: Corporate-owned devices are fully managed. Lesson: Mobile device management (MDM)
Crimper: The crimper presses the plug pins into the wires and locks the jacket strain relief. Lesson: Making a cable: stripper and crimper
Cross-platform virtualization: Cross-platform virtualization: run a different OS, e.g. Lesson: Legacy, cross-platform and application virtualization
Crossover: A on one end and B on the other makes a crossover cable (old PC-to-PC links; modern ports auto-detect with Auto-MDI-X). Lesson: T568A and T568B
Cursor drift/touch calibration: Cursor drift/touch calibration: the pointer moves by itself or taps land off target. Lesson: Cursor drift, calibration and stylus
D
Damaged ports: Damaged ports: lint in the charging port (clean gently with non-metal tools), bent pins, or loose port. Lesson: Connectivity, ports and liquid damage
Data loss/corruption: Data loss/corruption: files that won't open, file system errors: run a disk check (chkdsk), restore from backup, and check S.M.A.R.T. Lesson: Data loss/corruption, slow read/write and low IOPS
Database server: Database server: stores structured data for apps (inventory, orders). Lesson: File, print, mail, web, database, logs
DB9: Serial ports send one bit at a time over RS-232, using a 9-pin DB9 (technically DE-9) connector. Lesson: Serial (RS-232)
DC rails: The PSU converts AC to DC rails. Lesson: Output rails: 3.3 V, 5 V, 12 V
DDR: Each DDR (double data rate) generation is faster, uses lower voltage and is not compatible with the others: a board supports one generation. Lesson: DDR iterations
DDR generation: Match the DDR generation (DDR4 and DDR5 SODIMMs are keyed differently and do not fit each other). Lesson: Memory (RAM) in laptops
DDR3: DDR3 (1.5 V, up to ~2133 MT/s), DDR4 (1.2 V, ~2133-3200 MT/s), DDR5 (1.1 V, 4800 MT/s and up). Lesson: DDR iterations
DDR4: DDR3 (1.5 V, up to ~2133 MT/s), DDR4 (1.2 V, ~2133-3200 MT/s), DDR5 (1.1 V, 4800 MT/s and up). Lesson: DDR iterations
DDR5: DDR3 (1.5 V, up to ~2133 MT/s), DDR4 (1.2 V, ~2133-3200 MT/s), DDR5 (1.1 V, 4800 MT/s and up). Lesson: DDR iterations
Dead pixels: Dead pixels are always black; stuck pixels are stuck on one color. Lesson: Burn-in, dead pixels and flashing
Dedicated: Dedicated resources: hardware reserved for you alone (dedicated hosts): costs more, helps compliance and licensing. Lesson: Shared vs. dedicated resources, multitenancy
Default gateway: Devices on the same network talk directly; anything else goes to the default gateway, the router's address on the local network. Lesson: IPv4, subnet mask and gateway
Degraded performance: Degraded performance: low free storage, too many background apps, old OS, worn battery throttling the CPU, or overheating. Lesson: Overheating and degraded performance
Design capacity: Compare full charge capacity with design capacity. Lesson: Checking battery health
Detect and correct single-bit errors: ECC (error-correcting code) memory stores extra bits so it can detect and correct single-bit errors on the fly. Lesson: ECC vs. non-ECC
DFS: the FCC in the US) set allowed channels and power per country; some 5 GHz channels need DFS to avoid radar. Lesson: Channels, widths and regulations
DHCP: DHCP UDP 67 (server) and 68 (client) hands out IP settings. Lesson: Web, names and addresses
DHCP address changed: Check the cable/link lights, Wi-Fi association, and whether its DHCP address changed (use a reservation or static IP). Lesson: Connectivity issues
DHCP server: DHCP server: leases IP address, mask, gateway and DNS settings automatically. Lesson: Core server roles
Digitizer: The digitizer is the transparent layer that turns touch or pen input into coordinates. Lesson: Touch screen / digitizer
Digitizer issues: Digitizer issues: touch not working in one area, "ghost touches" or wrong taps. Lesson: Broken screen and digitizer issues
Dim image: Dim image: brightness/power-saving settings, ambient light sensor, failing backlight or inverter (CCFL), or an old projector lamp. Lesson: Color, dim image and audio
DIMM: DIMM (dual inline memory module) is the full-length stick for desktops and servers. Lesson: Form factors: DIMM and SODIMM
Direct burial: Direct burial cable (UTP or STP) has a tough, water-resistant jacket so it can be buried in the ground without conduit, e.g. Lesson: Direct burial and plenum-rated
Disconnect the internal battery: Before you open anything: AC adapter out, then disconnect the internal battery, and wear an ESD strap. Lesson: Read the service manual first
Disk Management: Open Disk Management: initialize (GPT), create a volume, format, and assign a letter. Lesson: Missing drives in the OS
Display burn-in: Display burn-in: a faint permanent ghost of a static image (logos, taskbars), mostly on OLED (and old plasma/CRT). Lesson: Burn-in, dead pixels and flashing
Display sizing/orientation: Display sizing/orientation: wrong scaling %, overscan on TVs, or the orientation set to portrait/rotated (Ctrl+Alt+arrow hotkeys on some systems). Lesson: Fuzzy, distorted and sizing/orientation
DisplayPort: DisplayPort: digital video + audio, PC monitors, supports daisy-chaining (MST); latches. Lesson: Video cables
Distorted image: Distorted image: wrong aspect ratio or resolution, stretched output, or a projector with no keystone correction. Lesson: Fuzzy, distorted and sizing/orientation
DKIM: DKIM publishes a public key so receivers can check the digital signature on each message. Lesson: TXT for spam management: SPF, DKIM, DMARC
DMARC: DMARC tells receivers what to do when SPF/DKIM checks fail (none, quarantine, reject) and where to send reports. Lesson: TXT for spam management: SPF, DKIM, DMARC
DNS: DNS port 53: UDP for normal lookups, TCP for zone transfers and large replies. Lesson: Web, names and addresses
DNS server: DNS server: turns names into IP addresses. Lesson: Core server roles
Docking station: A docking station turns a laptop into a desktop: one connection (often USB-C/Thunderbolt, or a proprietary dock connector) gives power/charging, several monitors, wired Ethernet, USB, audio, and sometimes expansion bays. Lesson: Docking station vs. port replicator
Document findings, actions and outcomes: Document findings, actions and outcomes Lesson: The six steps, continued
Double/echo images: Double/echo images (ghosting): a faint repeat of the image farther down the page. Lesson: Double/echo images and garbled print
Drawing pad: A drawing pad (graphics tablet) uses a pen for designers. Lesson: Trackpad, drawing pad, track point
Driver's installable options: Tray not recognized: the tray is not fully seated, a sensor or connector is dirty/damaged, or the driver's installable options don't list the add-on tray (so the PC never offers it). Lesson: Tray not recognized
Driver's orientation default: Check the app's page setup, the driver's orientation default, and print server defaults. Lesson: Incorrect page orientation
Drum: Lines down the printed pages (vertical streaks): on a laser, a scratched or dirty drum (imaging unit), dirty transfer roller, or debris on the fuser; on an inkjet, clogged nozzles (white lines/gaps) or a dirty… Lesson: Lines down the page
DSL: RJ11 (6P2C, up to 4 used): phone lines and DSL, smaller than RJ45. Lesson: Copper network connectors
Dual-channel: Dual-channel: two matched modules in the right slots (often same color, e.g. Lesson: Channel configurations
Duplex: Duplex: print both sides (saves paper; needs a duplex unit). Lesson: Configuration settings
DVI: DVI: digital (DVI-D), analog (DVI-A) or both (DVI-I); no audio. Lesson: Video cables
Dynamic: Dynamic addressing (DHCP) is automatic and right for most clients. Lesson: Static vs. dynamic
E
ECC: ECC (error-correcting code) memory stores extra bits so it can detect and correct single-bit errors on the fly. Lesson: ECC vs. non-ECC
Egress: Egress is data going out (usually billed per GB). Lesson: Metered utilization, ingress and egress
Elasticity: Elasticity: resources scale up and down automatically with demand, e.g. Lesson: Elasticity and availability
Enable Bluetooth: Enable Bluetooth on the phone/laptop Lesson: Bluetooth pairing, step by step
Enable pairing: Enable pairing (discoverable mode) on the accessory, often a long press Lesson: Bluetooth pairing, step by step
Encrypted tunnel: A VPN (virtual private network) builds an encrypted tunnel across the internet. Lesson: VPN
Energy efficiency: Energy efficiency is shown by the 80 PLUS rating: an efficient PSU wastes less power as heat. Lesson: Wattage and energy efficiency
Enter the appropriate PIN code: Enter the appropriate PIN code (or confirm the matching code) Lesson: Bluetooth pairing, step by step
eSATA: eSATA is external SATA with a shielded, sturdier connector (up to 2 m). Lesson: Hard drive cables: SATA and eSATA
Escalate: Step 3: test one thing at a time; if the theory fails, form a new one or escalate. Lesson: Using the steps well
eSIM: An eSIM is built into the phone and loaded with a carrier profile by QR code or app: no card to lose, and one phone can hold several profiles (e.g. Lesson: SIM and eSIM
Establish a plan of action: Establish a plan of action to resolve the problem and implement the solution (vendor instructions) Lesson: The six steps, continued
Establish a theory of probable cause: Establish a theory of probable cause (question the obvious); research if needed Lesson: The six steps
Ethernet: Ethernet: the business choice; give it a static IP or DHCP reservation so it never moves. Lesson: Device connectivity
Exclusion: An exclusion removes addresses from the scope so DHCP never hands them out (for static devices). Lesson: DHCP: scope, leases, reservations, exclusions
Extended read/write times: Extended read/write times: a dying HDD retrying bad sectors, a full or highly fragmented HDD, or an SSD with no free space. Lesson: Data loss/corruption, slow read/write and low IOPS
External interference: Intermittent wireless connectivity: weak signal at the edge of coverage, roaming between APs, channel overlap with neighbors, power-saving on the NIC, or external interference. Lesson: Intermittent wireless and external interference
F
F-type: RG-6 is used for cable TV and cable internet (cable modems), with F-type screw-on connectors. Lesson: Coaxial
Faded prints: Faded prints: low toner/ink, toner-save or draft mode, wrong paper type setting, or (laser) a failing transfer roller; on thermal, old paper or a worn element; on impact, a worn ribbon. Lesson: Faded prints and speckling
Fan considerations: Fan considerations: choose fan curves (silent vs. Lesson: Fans and temperature monitoring
Fan the paper: Multipage misfeed (several sheets at once): worn separation pad, humid or static paper, overfilled tray: fan the paper and replace the pad/rollers (maintenance kit). Lesson: Paper jams, not feeding, multipage misfeed
Fans: Fans move air: front intake, rear/top exhaust. Lesson: Cooling
Feed assembly: The feed assembly (platen roller) moves paper over the heating element (printhead). Lesson: Thermal printers
Feeder: Parts: ink cartridges, a printhead (built into the cartridge or fixed in the printer), a carriage and belt, a roller and feeder that move paper. Lesson: Inkjet printers
Fiber: Fiber (to the premises): fastest and most reliable, often symmetrical (e.g. Lesson: Fiber, cable and DSL
Field-replaceable: The maker's service manual shows the screw order and which parts are field-replaceable and which are soldered. Lesson: Read the service manual first
File synchronization: File synchronization keeps files the same across devices and the cloud: change a file on the laptop and it updates on the phone and web. Lesson: File synchronization
Fileshare: Fileshare server: central shared folders with permissions. Lesson: File, print, mail, web, database, logs
Fingerprint reader: Biometrics: a fingerprint reader or an IR face camera lets users sign in with "something you are" (e.g. Lesson: Physical privacy and security components
Finisher: The finisher staples, punches and folds. Lesson: Finishing issues: staple jams and hole punch
Fire hazard: A swollen battery (bulging case, lifted screen) is a fire hazard: stop using it, power off, do not puncture or charge it, and send it for proper disposal. Lesson: Battery health, swollen battery, charging
Firewall: A firewall filters traffic by rules (IP, port, protocol, application) between trusted and untrusted networks. Lesson: Patch panel and firewall
Firmware: MFDs run their own firmware. Lesson: Firmware
Flash drives: Flash drives (USB thumb drives): portable, often blocked by policy for security. Lesson: Removable and optical storage
Flashing screen: Flashing screen: loose cable, wrong refresh rate, a failing backlight or inverter, or a bad graphics driver. Lesson: Burn-in, dead pixels and flashing
Flatbed scanner: The flatbed scanner is the glass under the lid: for books, ID cards, photos and fragile or odd-sized pages. Lesson: ADF and flatbed scanner
Frozen print queue: A frozen print queue won't delete or move. Lesson: Multiple prints pending and frozen print queue
FTP: FTP uses TCP 20 (data) and 21 (control); sends credentials in cleartext. Lesson: File transfer and remote access
Full charge capacity: Compare full charge capacity with design capacity. Lesson: Checking battery health
Full punch waste bin: Hole punch issues: a full punch waste bin, holes in the wrong place (paper size/orientation setting), or the hole punch option not enabled in the driver. Lesson: Finishing issues: staple jams and hole punch
Fuser: Apply a maintenance kit at the page count the printer prompts: new fuser, pickup and separation rollers, transfer roller; then reset the page counter. Lesson: Laser printers
Fuzzy image: Fuzzy image: resolution not set to the panel's native resolution, or an analog VGA link at high resolution. Lesson: Fuzzy, distorted and sizing/orientation
G
Garbled print: Garbled print (random characters, symbols, pages of code): wrong or corrupt driver (e.g. Lesson: Double/echo images and garbled print
Global unicast: Key types: fe80::/10 link-local (auto, every interface), ::1 loopback, 2000::/3 global unicast. Lesson: IPv6
GPS services: GPS services use satellites: accurate (a few meters) outdoors, weak indoors, and they take power. Lesson: Location services
Green: They swap the orange and green pairs. Lesson: T568A and T568B
Grinding noise: A grinding noise comes from gears: a stripped or broken gear, a failing fuser drive, or something stuck in the paper path (a paper clip, a label). Lesson: Grinding noise
Grinding noises: Grinding noises from an HDD mean physical damage, like the head touching the platter or a failed bearing. Lesson: Grinding and clicking
H
Hardware virtualization: Running VMs well needs CPU hardware virtualization enabled in firmware: Intel VT-x or AMD-V (SVM), plus SLAT (EPT/RVI). Lesson: Virtualization support
HDMI: HDMI: digital video plus audio, TVs/projectors/monitors (2.0 = 18 Gbps, 2.1 = 48 Gbps). Lesson: Video cables
Headers: Headers are pin rows for case cables: front panel (power switch, reset, power and drive LEDs), USB 2.0/3.x front ports, front audio, fan headers (3-pin DC, 4-pin PWM), RGB lighting, and TPM. Lesson: Power connectors and headers
Headsets: Headsets connect by 3.5 mm jack, USB or Bluetooth. Lesson: Accessories
Heat sink: A heat sink draws heat from the CPU through metal fins. Lesson: Cooling
Heating element: The feed assembly (platen roller) moves paper over the heating element (printhead). Lesson: Thermal printers
High latency: High latency is delay (ms): congested links, long or satellite paths, overloaded routers or a busy Wi-Fi channel. Lesson: Slow speeds and high latency
Hole punch: Hole punch issues: a full punch waste bin, holes in the wrong place (paper size/orientation setting), or the hole punch option not enabled in the driver. Lesson: Finishing issues: staple jams and hole punch
Hotspot: Tethering shares a phone's cellular data with one device over USB, Bluetooth or Wi-Fi; a hotspot turns the phone into a small Wi-Fi access point for several devices. Lesson: Wireless connection methods
HSM: An HSM (hardware security module) is a separate device or card that creates, stores and uses many keys at high speed: for servers, certificate authorities and payments. Lesson: Encryption hardware: TPM and HSM
HTTP: HTTP TCP 80: web in cleartext. Lesson: Web, names and addresses
HTTPS: HTTPS TCP 443: web encrypted with TLS. Lesson: Web, names and addresses
Hundreds of meters: Multimode has a wider core (50/62.5 micron), cheaper LED/VCSEL light, and runs hundreds of meters: inside a building or data center. Lesson: Fiber: single-mode vs. multimode
Hybrid: Hybrid: mix of private/on-site and public, e.g. Lesson: Deployment models
hyper-threading/SMT: Core configurations: multicore (several cores per CPU), hyper-threading/SMT (2 threads per core), and hybrid designs with performance and efficiency cores. Lesson: CPU architecture and core configurations
Hypervisor: The hypervisor creates and runs VMs. Lesson: Hypervisors: Type 1 and Type 2
I
IaaS: IaaS (infrastructure): rent VMs, storage and networks; you manage the OS and up. Lesson: Service models: IaaS, PaaS, SaaS
Identify the problem: Identify the problem: gather info from the user, identify user changes, back up if needed, ask about environmental/infrastructure changes Lesson: The six steps
IMAP: IMAP TCP 143 keeps mail on the server and syncs folders across many devices. Lesson: Email ports
Improper charging: Improper charging: bad or underpowered cable/charger, dirty or damaged port, overheated battery, or a non-certified charger. Lesson: Battery health, swollen battery, charging
Inaccurate system date/time: Inaccurate system date/time that resets after power-off means a dead CMOS battery (CR2032 coin cell). Lesson: Swollen capacitors and wrong date/time
Incorrect color display: Incorrect color display: loose or bent-pin cable (a color channel missing, e.g. Lesson: Color, dim image and audio
Incorrect page orientation: Incorrect page orientation: landscape documents print portrait (cut off) or the other way round. Lesson: Incorrect page orientation
Ingress: Ingress is data going into the cloud (usually free). Lesson: Metered utilization, ingress and egress
Ink cartridges: Parts: ink cartridges, a printhead (built into the cartridge or fixed in the printer), a carriage and belt, a roller and feeder that move paper. Lesson: Inkjet printers
Inkjet: Lines down the printed pages (vertical streaks): on a laser, a scratched or dirty drum (imaging unit), dirty transfer roller, or debris on the fuser; on an inkjet, clogged nozzles (white lines/gaps) or a dirty… Lesson: Lines down the page
Input source: "No signal" with a working display: check the input source (HDMI 1 vs. Lesson: Incorrect input source and cabling issues
Intel: Intel uses LGA (land grid array): the pins are in the socket on the board (e.g. Lesson: CPU sockets and compatibility
Intel VT-x: Running VMs well needs CPU hardware virtualization enabled in firmware: Intel VT-x or AMD-V (SVM), plus SLAT (EPT/RVI). Lesson: Virtualization support
Intermittent internet connectivity: Intermittent internet connectivity with a stable LAN: ISP outages, a failing modem/ONT, bad coax/DSL line, or an overheating router. Lesson: Authentication failures and intermittent internet
Intermittent projector shutdown: Intermittent projector shutdown is usually overheating: clogged air filter, blocked vents, failed fan, or too hot a room. Lesson: Projector bulbs and shutdowns
Intermittent wireless connectivity: Intermittent wireless connectivity: weak signal at the edge of coverage, roaming between APs, channel overlap with neighbors, power-saving on the NIC, or external interference. Lesson: Intermittent wireless and external interference
internal/host-only: Network: virtual switches; VMs can be bridged (on the real LAN), NAT (share the host IP), internal/host-only or isolated. Lesson: VM requirements: storage, network, security
Into: Ingress is data going into the cloud (usually free). Lesson: Metered utilization, ingress and egress
Inverter: CCFL needs high-voltage AC, so an inverter board converts the laptop's DC to AC. Lesson: Backlights and the inverter
IoT devices: IoT devices (thermostats, cameras, smart locks, sensors) are easy to add but often weakly secured: change default passwords, update firmware, and put them on a separate VLAN. Lesson: Legacy/embedded systems and IoT
Ipconfig: Check with ipconfig: renew the lease (ipconfig /release then /renew), then ping the gateway, then a public IP, then a name. Lesson: Limited connectivity
IPS: IPS (in-plane switching) has the best color and wide viewing angles. Lesson: LCD panel types: IPS, TN, VA
IPv4: An IPv4 address is 32 bits, written as four octets (192.168.10.25). Lesson: IPv4, subnet mask and gateway
IPv6: IPv6 addresses are 128 bits, written as 8 groups of 4 hex digits: 2001:0db8:0000:0000:0000:ff00:0042:8329. Lesson: IPv6
IR face camera: Biometrics: a fingerprint reader or an IR face camera lets users sign in with "something you are" (e.g. Lesson: Physical privacy and security components
J
Jitter: Jitter is variation in latency between packets. Lesson: Jitter and poor VoIP quality
K
Kernel panic: macOS: a kernel panic restart with a "your computer restarted because of a problem" message; the spinning wait cursor is a hang. Lesson: Proprietary crash screens
Key: A single key can often be swapped: pop off the keycap and its small hinge/clip. Lesson: Keyboards and keys
Keyboard: A whole keyboard connects with a thin ribbon cable in a ZIF (zero insertion force) connector: flip up the latch, slide the cable out. Lesson: Keyboards and keys
Keystone: Distorted image: wrong aspect ratio or resolution, stretched output, or a projector with no keystone correction. Lesson: Fuzzy, distorted and sizing/orientation
Keystone jack: A punchdown tool seats each wire into the IDC (insulation-displacement) slots of a 110 block, 66 block, patch panel or keystone jack, and trims the extra wire. Lesson: Punchdown tool
Kill switch: Before you blame hardware, check the simple things: a closed privacy shutter (black picture), a camera/mic kill switch or F-key, the mic mute key light, and OS privacy settings that block apps. Lesson: Camera/webcam and microphone
L
LAN: A LAN (local area network) is one building or site, connected by switches. Lesson: Network types: LAN, WLAN, PAN
Lanes: PCIe (PCI Express) uses serial point-to-point lanes: slots come in x1, x4, x8, x16. Lesson: Expansion slots: PCI and PCIe
Laser: Lines down the printed pages (vertical streaks): on a laser, a scratched or dirty drum (imaging unit), dirty transfer roller, or debris on the fuser; on an inkjet, clogged nozzles (white lines/gaps) or a dirty… Lesson: Lines down the page
LC: LC (Lucent/little connector): small form factor, often duplex pairs, common on modern switches and SFP modules. Lesson: Fiber connectors: ST, SC, LC
LCD: An LCD uses liquid crystals that do not make light: a backlight shines through them. Lesson: LCD panel types: IPS, TN, VA
LDAP: LDAP TCP/UDP 389: query and update directory services such as user accounts in a domain directory. Lesson: Windows networking and directories
Lease: A lease is a loan of an address for a set time; clients renew at about 50% of the lease. Lesson: DHCP: scope, leases, reservations, exclusions
LED status indicators: Server drive bays and RAID controllers use LED status indicators: green/blinking = activity, amber/red = fault or predicted failure, blinking amber = rebuild or locate. Lesson: LED status indicators and audible alarms
LED-backlit: Modern LED-backlit LCDs do not use an inverter. Lesson: Backlights and the inverter
Legacy software/OS: Legacy software/OS: an old app that needs an unsupported OS runs in an isolated VM instead of on an old PC. Lesson: Legacy, cross-platform and application virtualization
Legacy/embedded: Legacy/embedded systems run fixed-purpose hardware for years and are hard to patch. Lesson: Legacy/embedded systems and IoT
LGA: Intel uses LGA (land grid array): the pins are in the socket on the board (e.g. Lesson: CPU sockets and compatibility
Lid, around the display: Laptop Wi-Fi antennas sit in the lid, around the display: high up and away from metal in the base. Lesson: Wi-Fi antenna connectors and placement
Lightning: Lightning is Apple's 8-pin reversible connector on older iPhones and iPads; newer models use USB-C. Lesson: Wired connection methods
Limited connectivity: Limited connectivity (no internet, local only): usually an APIPA 169.254.x.x address from a failed DHCP request, a wrong gateway, or a VLAN issue. Lesson: Limited connectivity
Link-local: Key types: fe80::/10 link-local (auto, every interface), ::1 loopback, 2000::/3 global unicast. Lesson: IPv6
Liquid: Liquid cooling (often an AIO: pump, tubes, radiator) moves heat to a radiator; check the pump and leaks. Lesson: Cooling
Liquid contact indicator: Liquid damage: power off at once, do not charge, dry it; check the liquid contact indicator (turns red). Lesson: Connectivity, ports and liquid damage
Liquid damage: Liquid damage: power off at once, do not charge, dry it; check the liquid contact indicator (turns red). Lesson: Connectivity, ports and liquid damage
Load balancer: Load balancer: spreads requests across several servers for speed and uptime. Lesson: Internet appliances
Local dimming zones: Mini-LED is still an LCD, but the backlight is thousands of tiny LEDs in local dimming zones, giving high brightness and better contrast than a normal LCD. Lesson: OLED and mini-LED
Loopback: Key types: fe80::/10 link-local (auto, every interface), ::1 loopback, 2000::/3 global unicast. Lesson: IPv6
Loopback plug: A loopback plug sends a port's transmit back into its own receive so you can test a NIC, switch port or serial port without another device. Lesson: Testing: cable tester and loopback plug
Low IOPS: Low IOPS (input/output operations per second): wrong drive type for the workload (slow HDDs under a database), a degraded or rebuilding RAID, or wrong cache settings. Lesson: Data loss/corruption, slow read/write and low IOPS
Low-band: 5G adds much more speed and lower latency: low-band (wide coverage), sub-6 GHz/mid-band, and mmWave (very fast, very short range, blocked by walls). Lesson: Cellular data: 3G, 4G, 5G
M
M key: Keys: M key (PCIe x4/NVMe, and some SATA), B key (SATA or PCIe x2), B+M fits both (usually SATA). Lesson: SSD form factors: M.2 and mSATA
M.2: Laptops use 2.5-inch SATA drives (7 mm or 9.5 mm thick) or M.2 cards. Lesson: Storage: HDD and SSD
M.2 2280: The common laptop size is M.2 2280 (22 mm wide, 80 mm long). Lesson: Storage: HDD and SSD
M.2 card: Wi-Fi and Bluetooth usually share one small M.2 card (often 2230, E-key). Lesson: Wireless cards
MAC address: A reservation always gives the same IP to a device's MAC address, great for printers. Lesson: DHCP: scope, leases, reservations, exclusions
MacOS: macOS: a kernel panic restart with a "your computer restarted because of a problem" message; the spinning wait cursor is a hang. Lesson: Proprietary crash screens
Mail: Phones sync mail, calendar and contacts with the company mail server (e.g. Lesson: Synchronization and data caps
Mail server: Mail server: sends (SMTP) and stores (IMAP/POP3) email. Lesson: File, print, mail, web, database, logs
main/aux: Thin cables run through the hinge to tiny snap-on connectors on the card (often labeled main/aux or 1/2). Lesson: Wi-Fi antenna connectors and placement
Malware: Malware signs: pop-ups, fast battery drain, high data use, unknown apps, fake security alerts. Lesson: Malware and cannot install apps
MAN: A MAN (metropolitan) spans a city: linking Kibble's HQ and stores across town. Lesson: Network types: MAN, WAN, SAN
Managed: A managed switch can be configured: VLANs, port security, QoS, port mirroring, link aggregation, monitoring (SNMP). Lesson: Switches: managed and unmanaged
Many kilometers: Single-mode has a tiny core (~9 micron), uses lasers, and runs many kilometers: building-to-building and ISP links. Lesson: Fiber: single-mode vs. multimode
MDM: MDM lets IT manage phones centrally. Lesson: Mobile device management (MDM)
MDM policy: Cannot install apps: not enough storage, OS version too old, app not compatible, store account/payment issue, or MDM policy blocks it. Lesson: Malware and cannot install apps
Memory cards: Memory cards: SD (SDHC up to 32 GB, SDXC up to 2 TB), microSD for phones and cameras. Lesson: Removable and optical storage
Metered utilization: Metered utilization: you pay for what you use: compute hours, storage GB per month, requests. Lesson: Metered utilization, ingress and egress
Mic mute: Before you blame hardware, check the simple things: a closed privacy shutter (black picture), a camera/mic kill switch or F-key, the mic mute key light, and OS privacy settings that block apps. Lesson: Camera/webcam and microphone
MicroATX: microATX (mATX): 9.6 x 9.6 in (244 x 244 mm), up to 4 slots, fits most ATX cases. Lesson: Motherboard form factors
Microphones: The webcam sits in the top bezel of the lid, usually with the microphones next to it. Lesson: Camera/webcam and microphone
MicroUSB: microUSB was the standard on older Android phones; miniUSB is older still (cameras, GPS units). Lesson: Wired connection methods
Microwave ovens: On 2.4 GHz the classic sources are microwave ovens, cordless phones, Bluetooth and baby monitors; thick walls, metal shelves and water also absorb signal. Lesson: Intermittent wireless and external interference
Mini-ITX: Mini-ITX (ITX): 6.7 x 6.7 in (170 x 170 mm), 1 slot, for small PCs like a register. Lesson: Motherboard form factors
Mini-LED: Mini-LED is still an LCD, but the backlight is thousands of tiny LEDs in local dimming zones, giving high brightness and better contrast than a normal LCD. Lesson: OLED and mini-LED
MiniUSB: microUSB was the standard on older Android phones; miniUSB is older still (cameras, GPS units). Lesson: Wired connection methods
Miswires: A cable tester checks each wire: continuity, opens, shorts, miswires, split pairs (wiremap). Lesson: Testing: cable tester and loopback plug
MmWave: 5G adds much more speed and lower latency: low-band (wide coverage), sub-6 GHz/mid-band, and mmWave (very fast, very short range, blocked by walls). Lesson: Cellular data: 3G, 4G, 5G
Modular: A modular PSU lets you attach only the cables you need: better airflow, tidier builds (semi-modular has the main cables fixed). Lesson: 20+4 pin connector, modular and redundant PSUs
Molex: Molex: 4-pin peripheral power from the PSU (+12 V and +5 V) for old drives, fans and adapters. Lesson: Device connectors
mSATA: mSATA is an older, smaller card using the SATA interface, found in older laptops. Lesson: SSD form factors: M.2 and mSATA
Multimode: Multimode has a wider core (50/62.5 micron), cheaper LED/VCSEL light, and runs hundreds of meters: inside a building or data center. Lesson: Fiber: single-mode vs. multimode
Multipage misfeed: Multipage misfeed (several sheets at once): worn separation pad, humid or static paper, overfilled tray: fan the paper and replace the pad/rollers (maintenance kit). Lesson: Paper jams, not feeding, multipage misfeed
Multipart paper: They are the only type that can print multipart paper (carbon/carbonless copies) in one pass, often tractor-fed. Lesson: Impact printers
Multisocket: Multisocket boards hold two or more CPUs: servers and high-end workstations. Lesson: CPU sockets and compatibility
Multitenancy: Multitenancy: many customers (tenants) share one platform or app instance while their data stays logically separated. Lesson: Shared vs. dedicated resources, multitenancy
MX: MX names the mail server(s) for a domain, with a priority (lower = preferred). Lesson: DNS record types
N
NAT: The SOHO router uses NAT to share one public address (assigned by the ISP, unique on the internet) among all inside devices. Lesson: Private vs. public addresses
Native resolution: Fuzzy image: resolution not set to the panel's native resolution, or an analog VGA link at high resolution. Lesson: Fuzzy, distorted and sizing/orientation
Near-field scanner features: Near-field scanner features: an NFC reader in the palm rest reads a badge or smart card tapped within a few centimeters ("something you have"). Lesson: Physical privacy and security components
NetBIOS over TCP/IP (NetBT): NetBIOS over TCP/IP (NetBT) ports 137-139: legacy Windows name service (UDP 137), datagram (UDP 138) and session (TCP 139). Lesson: Windows networking and directories
Network: Network: virtual switches; VMs can be bridged (on the real LAN), NAT (share the host IP), internal/host-only or isolated. Lesson: VM requirements: storage, network, security
Network tap: A network tap sits inline and copies all traffic to a monitoring tool. Lesson: Finding and watching: toner probe, tap, Wi-Fi analyzer
NFC: NFC works at a few centimeters: tap to pay, tap a badge, tap to pair. Lesson: Wireless connection methods
NIC: The NIC (network interface card) connects a host to the network: built-in, add-on card or USB. Lesson: NIC and MAC address
NIC, switch port or serial port: A loopback plug sends a port's transmit back into its own receive so you can test a NIC, switch port or serial port without another device. Lesson: Testing: cable tester and loopback plug
No backlight: OLED pixels make their own light, so there is no backlight: perfect blacks, thin panels, but a risk of burn-in from static images. Lesson: OLED and mini-LED
No power: No power (no lights, no fans): check the outlet with another device, the power cord, the PSU switch and input voltage selector, then the front-panel power button header and the 24-pin plug. Lesson: No power and burning smell
Non-ECC: Non-ECC is standard in desktops and laptops: cheaper and slightly faster. Lesson: ECC vs. non-ECC
None, quarantine, reject: DMARC tells receivers what to do when SPF/DKIM checks fail (none, quarantine, reject) and where to send reports. Lesson: TXT for spam management: SPF, DKIM, DMARC
NTP: NTP server: keeps every clock in sync (UDP 123); wrong time breaks logins and certificates. Lesson: Core server roles
NVMe: PCIe connects the drive straight to PCIe lanes; NVMe is the protocol built for flash over PCIe. Lesson: SSD interfaces: SATA, SAS, PCIe, NVMe
NVMe (PCIe): An M.2 slot can be SATA, NVMe (PCIe), or both: check the manual. Lesson: Storage: HDD and SSD
O
OLED: OLED pixels make their own light, so there is no backlight: perfect blacks, thin panels, but a risk of burn-in from static images. Lesson: OLED and mini-LED
ONT: An ONT (optical network terminal) converts the provider's fiber into Ethernet at the customer site. Lesson: Cable modem, DSL modem, ONT
Opens: A cable tester checks each wire: continuity, opens, shorts, miswires, split pairs (wiremap). Lesson: Testing: cable tester and loopback plug
Optical drives: Optical drives: CD (~700 MB), DVD (4.7 GB single layer, 8.5 GB dual layer), Blu-ray (25 GB single, 50 GB dual). Lesson: Removable and optical storage
Orange: They swap the orange and green pairs. Lesson: T568A and T568B
Orientation: Orientation: portrait or landscape. Lesson: Configuration settings
Out: Egress is data going out (usually billed per GB). Lesson: Metered utilization, ingress and egress
Overheating: Overheating: dust-clogged heat sinks and filters, failed fans, dried thermal paste, blocked vents. Lesson: Overheating, random shutdowns, unusual noise
P
PaaS: PaaS (platform): the provider runs OS and runtime; you deploy your code and data (developers). Lesson: Service models: IaaS, PaaS, SaaS
Palm rest (top cover): Some keyboards come off from the top; on many thin laptops the keyboard is riveted into the palm rest (top cover), so you replace the whole assembly. Lesson: Keyboards and keys
PAN: Bluetooth is a short-range PAN (about 10 m for common devices) for headsets, keyboards and speakers. Lesson: Wireless connection methods
Paper jams: Paper jams: wrong paper weight/type, damp or curled paper, torn scraps left inside, worn rollers. Lesson: Paper jams, not feeding, multipage misfeed
Paper not feeding: Paper not feeding: worn or dirty pickup roller, tray not seated, paper guides too tight. Lesson: Paper jams, not feeding, multipage misfeed
Passive: RFID (radio-frequency identification) reads tags, often passive (no battery, powered by the reader's signal), from centimeters to several meters: inventory, pallets, access badges. Lesson: NFC and RFID
Patch panel: A punchdown tool seats each wire into the IDC (insulation-displacement) slots of a 110 block, 66 block, patch panel or keystone jack, and trims the extra wire. Lesson: Punchdown tool
PCI: PCI is the old 32-bit shared parallel bus (133 MB/s): legacy cards only. Lesson: Expansion slots: PCI and PCIe
PCIe: PCIe connects the drive straight to PCIe lanes; NVMe is the protocol built for flash over PCIe. Lesson: SSD interfaces: SATA, SAS, PCIe, NVMe
PCL: The page description language matters: PCL (Printer Command Language) is fast and common for office text, and somewhat printer-dependent. Lesson: Drivers: PCL and PostScript
Performance and efficiency cores: Core configurations: multicore (several cores per CPU), hyper-threading/SMT (2 threads per core), and hybrid designs with performance and efficiency cores. Lesson: CPU architecture and core configurations
PGA: AMD used PGA for AM4 (pins on the CPU) and moved to LGA with AM5. Lesson: CPU sockets and compatibility
Physical MAC address: Each has a physical MAC address: 48 bits in hex, like 3C:52:82:1A:4F:07. Lesson: NIC and MAC address
Pickup roller: Paper not feeding: worn or dirty pickup roller, tray not seated, paper guides too tight. Lesson: Paper jams, not feeding, multipage misfeed
Ping: Ping the printer, check the port in the driver (Standard TCP/IP port points to the right IP), and for USB, try another cable/port. Lesson: Connectivity issues
Pixel density: Pixel density (PPI) is pixels per inch: the same resolution looks sharper on a smaller screen. Lesson: Display attributes
Plenum spaces: Plenum-rated cable has a fire-resistant, low-smoke jacket for plenum spaces (air-handling areas above drop ceilings or under raised floors). Lesson: Direct burial and plenum-rated
Plenum-rated: Plenum-rated cable has a fire-resistant, low-smoke jacket for plenum spaces (air-handling areas above drop ceilings or under raised floors). Lesson: Direct burial and plenum-rated
Plus audio: HDMI: digital video plus audio, TVs/projectors/monitors (2.0 = 18 Gbps, 2.1 = 48 Gbps). Lesson: Video cables
PoE: PoE sends power over the Ethernet cable to APs, IP cameras and VoIP phones. Lesson: Power over Ethernet (PoE)
PoE injector: A PoE injector adds power to one cable from a regular switch. Lesson: Power over Ethernet (PoE)
PoE switch: A PoE switch powers its ports directly. Lesson: Power over Ethernet (PoE)
Policy enforcement: Policy enforcement: require a PIN, encryption, OS version, block jailbroken/rooted phones, remote lock/wipe. Lesson: Mobile device management (MDM)
Poor battery health: Poor battery health: short runtime; check battery health in settings, cut screen brightness and background apps, or replace. Lesson: Battery health, swollen battery, charging
Poor VoIP quality: Poor VoIP quality (robotic voice, gaps, echo, dropped calls) comes from jitter, packet loss and latency (aim for under ~150 ms one way and low jitter). Lesson: Jitter and poor VoIP quality
Poor/no connectivity: Poor/no connectivity: airplane mode, Wi-Fi/Bluetooth off, out of range, wrong saved network, or carrier/SIM issue; toggle radios, forget and rejoin. Lesson: Connectivity, ports and liquid damage
POP3: POP3 TCP 110 downloads mail to one device and usually deletes it from the server. Lesson: Email ports
Port flapping: Port flapping: a switch port goes up and down again and again (link up/link down in the switch log). Lesson: Port flapping
Port replicator: A port replicator is simpler: it just copies (replicates) the laptop's ports to one box so cables stay plugged in. Lesson: Docking station vs. port replicator
POST: POST (power-on self-test) checks CPU, RAM and video before booting. Lesson: POST beeps and blank screen
POST beeps: POST beeps are codes: one short beep is usually OK; patterns (e.g. Lesson: POST beeps and blank screen
PostScript: PostScript is device-independent and best for graphics and design work (same output on any PS printer). Lesson: Drivers: PCL and PostScript
Power budget: Watch the switch's total power budget. Lesson: Power over Ethernet (PoE)
Power connectors: Power connectors on the board: 24-pin ATX main power and 4/8-pin ATX12V (EPS) CPU power near the socket. Lesson: Power connectors and headers
Power off and unplug at once: Burning smell: power off and unplug at once. Lesson: No power and burning smell
Predicted: failure warning at boot or in a tool means failure is predicted**: back up now and replace the drive. Lesson: S.M.A.R.T. failure
Print server: Print server: manages queues and drivers for many printers. Lesson: File, print, mail, web, database, logs
Printer share: A printer share shares a printer attached to one workstation: the host PC must be on for others to print. Lesson: Public/shared devices: printer share vs. print server
Printhead: Parts: ink cartridges, a printhead (built into the cartridge or fixed in the printer), a carriage and belt, a roller and feeder that move paper. Lesson: Inkjet printers
Privacy screen filter: Add a privacy screen filter against shoulder surfing and a cable lock slot against theft. Lesson: Physical privacy and security components
Privacy shutter: Before you blame hardware, check the simple things: a closed privacy shutter (black picture), a camera/mic kill switch or F-key, the mic mute key light, and OS privacy settings that block apps. Lesson: Camera/webcam and microphone
Private: Private IPv4 ranges (RFC 1918) are used inside networks and are not routed on the internet: 10.0.0.0/8, 172.16.0.0-172.31.255.255 (/12), 192.168.0.0/16. Lesson: Private vs. public addresses
Proxy server: Proxy server: makes web requests on behalf of clients, for caching, filtering and logging. Lesson: Internet appliances
PSU tester: Test the PSU with a PSU tester or multimeter. Lesson: No power and burning smell
Public: The SOHO router uses NAT to share one public address (assigned by the ISP, unique on the internet) among all inside devices. Lesson: Private vs. public addresses
Punchdown block: A punchdown block is where wires terminate in a closet or patch panel: 66 blocks (older phone) and 110 blocks (data, Cat 5e and up). Lesson: Copper network connectors
Punchdown tool: A punchdown tool seats each wire into the IDC (insulation-displacement) slots of a 110 block, 66 block, patch panel or keystone jack, and trims the extra wire. Lesson: Punchdown tool
Q
QoS: Fix with QoS to prioritize voice, a separate voice VLAN, wired phones, and enough bandwidth (watch the upload). Lesson: Jitter and poor VoIP quality
Quality: Quality: resolution in dpi (e.g. Lesson: Configuration settings
R
RAID 0: RAID 0 (striping): 2+ drives, fastest, all capacity, no fault tolerance: one drive dies, all data lost. Lesson: RAID 0, 1 and 5
RAID 1: RAID 1 (mirroring): 2 drives, identical copies, survives 1 failure, 50% usable. Lesson: RAID 0, 1 and 5
RAID 5: RAID 5 (striping with parity): 3+ drives, survives 1 drive failure, usable = (n-1) x drive size. Lesson: RAID 0, 1 and 5
RAID 6: RAID 6 (double parity): 4+ drives, survives 2 drive failures, usable = (n-2). Lesson: RAID 6 and 10
RAID 10: RAID 10 (1+0, a stripe of mirrors): 4+ drives (even number), fast and fault tolerant, 50% usable; survives one failure per mirror pair. Lesson: RAID 6 and 10
RAID failure: RAID failure: a degraded array still works but has lost fault tolerance; replace the failed drive with a matching one and let it rebuild (slow, risky time). Lesson: RAID failure and array missing
Random shutdown: Random shutdown: overheating, a failing or undersized PSU, or loose power cables. Lesson: Overheating, random shutdowns, unusual noise
RDP: RDP TCP 3389 (UDP 3389 too): Windows Remote Desktop graphical sessions. Lesson: File transfer and remote access
Rebuild: RAID failure: a degraded array still works but has lost fault tolerance; replace the failed drive with a matching one and let it rebuild (slow, risky time). Lesson: RAID failure and array missing
Recognize data caps: Learn to recognize data caps: large cloud uploads (photos, videos) over cellular can blow a plan. Lesson: Synchronization and data caps
Redundant: A redundant PSU setup has two or more hot-swappable units in a server; if one fails, the other carries the load. Lesson: 20+4 pin connector, modular and redundant PSUs
Refresh rate: Refresh rate (Hz) is redraws per second: 60 Hz office, 120-240 Hz smoother. Lesson: Display attributes
Registered (buffered): Servers often use registered (buffered) ECC modules too. Lesson: ECC vs. non-ECC
Regulations: Regulations (e.g. Lesson: Channels, widths and regulations
Remove debris: Maintenance: replace paper with the right type and side facing up, clean the heating element with isopropyl alcohol, and remove debris (label glue, dust) from the path. Lesson: Thermal printers
Replace cartridges: Maintenance: clean printheads with the built-in utility (clogged nozzles leave lines/gaps), replace cartridges, calibrate (align the heads after a cartridge change), and clear jams by opening the access door and… Lesson: Inkjet printers
Replace paper: Maintenance: replace paper with the right type and side facing up, clean the heating element with isopropyl alcohol, and remove debris (label glue, dust) from the path. Lesson: Thermal printers
Replace the printhead: Maintenance: replace the ribbon when print fades, replace the printhead when dots are missing (bent or broken pins), and replace paper, keeping tractor feed aligned. Lesson: Impact printers
Replace the ribbon: Maintenance: replace the ribbon when print fades, replace the printhead when dots are missing (bent or broken pins), and replace paper, keeping tractor feed aligned. Lesson: Impact printers
Replace toner: On the exam (3.8) know the maintenance: Replace toner (often with the drum in one cartridge). Lesson: Laser printers
Reservation: A reservation always gives the same IP to a device's MAC address, great for printers. Lesson: DHCP: scope, leases, reservations, exclusions
Reset the lamp timer: Replace with the exact lamp, let it cool first, do not touch the glass, and reset the lamp timer. Lesson: Projector bulbs and shutdowns
Reset the page counter: Apply a maintenance kit at the page count the printer prompts: new fuser, pickup and separation rollers, transfer roller; then reset the page counter. Lesson: Laser printers
Resolution: Resolution is pixels across x down (1920x1080 FHD, 2560x1440 QHD, 3840x2160 4K UHD). Lesson: Display attributes
Restart the Print Spooler service: Fix: cancel jobs; if stuck, restart the Print Spooler service (services.msc or net stop/start spooler), clearing the spool folder if needed. Lesson: Multiple prints pending and frozen print queue
RFID: RFID (radio-frequency identification) reads tags, often passive (no battery, powered by the reader's signal), from centimeters to several meters: inventory, pallets, access badges. Lesson: NFC and RFID
RG-6: RG-6 is used for cable TV and cable internet (cable modems), with F-type screw-on connectors. Lesson: Coaxial
Ribbon: Impact (dot matrix) printers strike pins through an inked ribbon. Lesson: Impact printers
Ribbon cable: A whole keyboard connects with a thin ribbon cable in a ZIF (zero insertion force) connector: flip up the latch, slide the cable out. Lesson: Keyboards and keys
RJ11: RJ11 (6P2C, up to 4 used): phone lines and DSL, smaller than RJ45. Lesson: Copper network connectors
RJ45: RJ45 (8P8C): Ethernet, 8 pins. Lesson: Copper network connectors
Roller: Parts: ink cartridges, a printhead (built into the cartridge or fixed in the printer), a carriage and belt, a roller and feeder that move paper. Lesson: Inkjet printers
Router: A router forwards traffic between networks using IP addresses: it is the default gateway and does NAT at a SOHO. Lesson: Router, switch, access point
S
S.M.A.R.T: S.M.A.R.T. (Self-Monitoring, Analysis and Reporting Technology) tracks drive health: reallocated sectors, pending sectors, read errors, temperature, SSD wear. Lesson: S.M.A.R.T. failure
S.M.A.R.T. failure: A **S.M.A.R.T. Lesson: S.M.A.R.T. failure
SaaS: SaaS (software): a complete app over the internet, e.g. Lesson: Service models: IaaS, PaaS, SaaS
Same: Use the same standard on both ends for a straight-through cable (B is most common). Lesson: T568A and T568B
SAN: A SAN (storage area network) is a dedicated high-speed network that gives servers block-level access to shared storage (Fibre Channel or iSCSI). Lesson: Network types: MAN, WAN, SAN
Sandbox: A sandbox VM is isolated: open a suspicious file or test risky software without touching the host, then roll back with a snapshot. Lesson: Why virtual machines?
SAS: SAS is the enterprise interface (12-22.5 Gbps, dual-ported, hot-swap) in servers. Lesson: SSD interfaces: SATA, SAS, PCIe, NVMe
SATA: Laptops use 2.5-inch SATA drives (7 mm or 9.5 mm thick) or M.2 cards. Lesson: Storage: HDD and SSD
Satellite: Satellite: works almost anywhere with sky view. Lesson: Satellite, cellular and WISP
SC: SC (subscriber/standard connector): square, push-pull snap. Lesson: Fiber connectors: ST, SC, LC
SCADA: SCADA (supervisory control and data acquisition) runs industrial equipment: conveyor belts, HVAC, power. Lesson: Legacy/embedded systems and IoT
Scan to email: Scan to email: the MFD sends the file via an SMTP server (needs the server name, port and often credentials). Lesson: Network scan services
Scan to SMB: Scan to SMB (folder): saves to a Windows share (\\server\scans, TCP 445) with an account that can write there. Lesson: Network scan services
Scope: A scope is the range of addresses DHCP can hand out for a subnet, plus options (mask, gateway, DNS). Lesson: DHCP: scope, leases, reservations, exclusions
Secure Boot: Secure Boot (UEFI) only runs bootloaders signed with trusted keys, blocking boot-level malware (rootkits). Lesson: Passwords, Secure Boot and TPM features
Secured prints: Secured prints (PIN or "pull" printing): the job waits in memory until the user releases it at the device, so nothing sits in the tray. Lesson: Security
Security: Security: patch every guest OS like a real PC, use antivirus, and watch for VM escape; a compromised host exposes all its VMs. Lesson: VM requirements: storage, network, security
Security vulnerabilities: Update it from the vendor to fix bugs, add features and patch security vulnerabilities. Lesson: Firmware
Separation pad: Multipage misfeed (several sheets at once): worn separation pad, humid or static paper, overfilled tray: fan the paper and replace the pad/rollers (maintenance kit). Lesson: Paper jams, not feeding, multipage misfeed
Serial: Serial ports send one bit at a time over RS-232, using a 9-pin DB9 (technically DE-9) connector. Lesson: Serial (RS-232)
Service manual: The maker's service manual shows the screw order and which parts are field-replaceable and which are soldered. Lesson: Read the service manual first
Set-up location: Set-up location: stable surface, ventilation and clearance for trays and doors, near the right power outlet (not a UPS for lasers), network drop, and away from heat, dust and direct sun. Lesson: Unboxing and set-up location
Shared resources: Shared resources: your VMs run on hardware other customers use too: cheaper. Lesson: Shared vs. dedicated resources, multitenancy
Shares the host OS kernel: A container packages an app with its libraries and settings, but shares the host OS kernel. Lesson: Containers
Shipping tape, locks and foam: Unbox properly: big MFDs are heavy, so use two people or a lift; let a device that came in from the cold reach room temperature to avoid condensation; remove all shipping tape, locks and foam (toner/drum and scanner… Lesson: Unboxing and set-up location
Shorts: A cable tester checks each wire: continuity, opens, shorts, miswires, split pairs (wiremap). Lesson: Testing: cable tester and loopback plug
Sideloaded: Remove unknown apps (especially sideloaded ones or those with device admin rights), update, scan, and factory reset if needed. Lesson: Malware and cannot install apps
Signal strength (dBm): A Wi-Fi analyzer shows nearby networks, signal strength (dBm), channels and overlap so you can pick clear channels and find dead spots. Lesson: Finding and watching: toner probe, tap, Wi-Fi analyzer
SIM: The SIM (subscriber identity module) card holds the subscriber identity (IMSI) that ties the phone to a carrier account. Lesson: SIM and eSIM
Single-channel: Single-channel: one path. Lesson: Channel configurations
Single-mode: Single-mode has a tiny core (~9 micron), uses lasers, and runs many kilometers: building-to-building and ISP links. Lesson: Fiber: single-mode vs. multimode
Site-to-site: Site-to-site: routers/firewalls join two offices permanently, e.g. Lesson: VPN
Slow network speeds: Slow network speeds: a saturated link (backups, cloud sync, video), a port negotiated at 100 Mbps or half duplex (bad cable/old Cat), weak Wi-Fi, or a limited ISP plan. Lesson: Slow speeds and high latency
Sluggish performance: Sluggish performance at the hardware level: thermal throttling, too little RAM (constant paging to disk), a failing HDD, single-channel memory, or a power plan set to battery saver. Lesson: Sluggish performance and application crashes
SMB/CIFS: SMB/CIFS TCP 445: Windows file and printer sharing directly over TCP. Lesson: Windows networking and directories
SMTP: SMTP TCP 25 sends mail (client to server, server to server). Lesson: Email ports
Snapshot: A sandbox VM is isolated: open a suspicious file or test risky software without touching the host, then roll back with a snapshot. Lesson: Why virtual machines?
Socket: The CPU must match the board's socket and chipset. Lesson: CPU sockets and compatibility
SODIMM: Upgradeable laptops use SODIMM modules (small outline DIMM), in a slot at an angle that clicks down. Lesson: Memory (RAM) in laptops
Soldered LPDDR: Many thin laptops use soldered LPDDR memory with no slot: it cannot be upgraded. Lesson: Memory (RAM) in laptops
Sound card: Sound card: better audio, more channels. Lesson: Expansion cards
Spam gateway: Spam gateway: filters incoming mail for spam, phishing and malware before the mail server. Lesson: Internet appliances
Speakers: Speakers can be wired or Bluetooth. Lesson: Accessories
Special thermal paper: Direct thermal printers (labels, receipts) heat special thermal paper that darkens where heated: no ink or toner. Lesson: Thermal printers
SPF: SPF lists the servers allowed to send mail for the domain. Lesson: TXT for spam management: SPF, DKIM, DMARC
Spindle speed: Spindle speed sets performance: 5,400 rpm (laptops, cheap), 7,200 rpm (desktops), 10,000 and 15,000 rpm (servers). Lesson: Hard drives: speeds and sizes
Split pairs: A cable tester checks each wire: continuity, opens, shorts, miswires, split pairs (wiremap). Lesson: Testing: cable tester and loopback plug
SSH: SSH TCP 22: encrypted command line (also SFTP/SCP). Lesson: File transfer and remote access
ST: ST (straight tip): round, bayonet twist-lock. Lesson: Fiber connectors: ST, SC, LC
Staple jams: Staple jams: wrong staple cartridge, too many sheets for the stapler limit, or a bent staple stuck in the head; open the finisher, clear the jam, reseat the cartridge. Lesson: Finishing issues: staple jams and hole punch
Static: Static addresses are typed in by hand and never change: use them for routers, servers, printers and network gear that others must always find. Lesson: Static vs. dynamic
Static IP or DHCP reservation: Ethernet: the business choice; give it a static IP or DHCP reservation so it never moves. Lesson: Device connectivity
Stop error: Windows: the blue (or black) stop error screen with a stop code (e.g. Lesson: Proprietary crash screens
Stop using the drive: Both are mechanical failures: stop using the drive, back up whatever you can at once, and replace it. Lesson: Grinding and clicking
Storage: Storage: room for each virtual disk file and its snapshots; fast SSD storage. Lesson: VM requirements: storage, network, security
STP: STP (shielded) adds foil/braid for noisy places (motors, machinery) and must be grounded. Lesson: Twisted pair: UTP, STP and categories
Stylus: A stylus may be passive (works like a fingertip) or active (has electronics, may need pairing and a charge). Lesson: Accessories
Stylus not working: Stylus not working: an active stylus needs charge and pairing (Bluetooth); check the tip, and confirm the device supports that stylus type. Lesson: Cursor drift, calibration and stylus
Subnet mask: The subnet mask (255.255.255.0 = /24) shows which part is the network and which is the host. Lesson: IPv4, subnet mask and gateway
Switch: A switch connects devices in one LAN and forwards frames by MAC address, port to port. Lesson: Switches: managed and unmanaged
Swollen battery: A swollen battery (bulging case, lifted screen) is a fire hazard: stop using it, power off, do not puncture or charge it, and send it for proper disposal. Lesson: Battery health, swollen battery, charging
Swollen capacitors: Swollen capacitors on the motherboard (bulging or leaking tops) cause random reboots and instability. Lesson: Swollen capacitors and wrong date/time
Syslog: Syslog server: collects log messages from routers, switches, firewalls and servers in one place (UDP 514). Lesson: File, print, mail, web, database, logs
T
TCP: TCP is connection-oriented: three-way handshake (SYN, SYN-ACK, ACK), sequencing, acknowledgments and retransmission. Lesson: TCP vs. UDP
Telnet: Telnet TCP 23: remote command line in cleartext; replace with SSH. Lesson: File transfer and remote access
Temperature monitoring: Firmware shows temperature monitoring for CPU and system, fan speeds and voltages, and can set alarms or shutdown thresholds. Lesson: Fans and temperature monitoring
Test connectivity: Test connectivity: play audio, scan a barcode, type a key Lesson: Bluetooth pairing, step by step
Test the theory: Test the theory to determine the cause; if not confirmed, new theory or escalate Lesson: The six steps
Test/development: Test/development: build and test patches, updates and apps on VMs that copy production before rolling them out. Lesson: Why virtual machines?
Tethering: Tethering shares a phone's cellular data with one device over USB, Bluetooth or Wi-Fi; a hotspot turns the phone into a small Wi-Fi access point for several devices. Lesson: Wireless connection methods
Thermal pads: Thermal pads do the same for VRMs, memory and SSDs, often in laptops. Lesson: Cooling
Thermal paste: Thermal paste fills tiny gaps between CPU and heat sink (pea-size dot, reapply if removed). Lesson: Cooling
Throttles: The CPU throttles (slows) and finally the system shuts off. Lesson: Overheating, random shutdowns, unusual noise
Thunderbolt: Thunderbolt joins PCIe data, DisplayPort video and power: TB 1/2 used the Mini DisplayPort plug (10/20 Gbps); TB 3 and 4 use USB-C at 40 Gbps and can daisy-chain devices. Lesson: USB 2.0, USB 3.0 and Thunderbolt
TN: Three panel types: TN (twisted nematic) is fast and cheap but has poor viewing angles and color. Lesson: LCD panel types: IPS, TN, VA
Toner probe: A toner probe (tone generator + inductive probe) traces an unlabeled cable: clip the tone onto one end, listen for it at the patch panel. Lesson: Finding and watching: toner probe, tap, Wi-Fi analyzer
Toner vacuum: Clean with a toner vacuum (not a household vacuum) and isopropyl alcohol on rollers. Lesson: Laser printers
TPM: A TPM (Trusted Platform Module) is a chip (or firmware) on the motherboard that stores encryption keys, measures the boot process, and unlocks full-disk encryption like BitLocker only if the system has not been… Lesson: Encryption hardware: TPM and HSM
TPM security features: TPM security features are switched on in firmware (often "PTT" on Intel, "fTPM" on AMD) for BitLocker and Windows 11. Lesson: Passwords, Secure Boot and TPM features
Track point: A track point is the small pointing stick in the middle of some keyboards. Lesson: Trackpad, drawing pad, track point
Trackpad: A trackpad (touchpad) senses finger movement and gestures; it can be disabled by an F-key or setting, which is a common "my mouse is dead" ticket. Lesson: Trackpad, drawing pad, track point
Tray not recognized: Tray not recognized: the tray is not fully seated, a sensor or connector is dirty/damaged, or the driver's installable options don't list the add-on tray (so the PC never offers it). Lesson: Tray not recognized
Tray settings: Tray settings: which tray holds which paper size/type (letter, legal, labels, envelopes) and the default source. Lesson: Configuration settings
Triple/quad-channel: Triple/quad-channel on workstation and server boards. Lesson: Channel configurations
TXT: TXT holds free text, mainly used for verification and email security. Lesson: DNS record types
Type 2 (hosted): Type 2 (hosted) runs as an application on top of a normal OS (Windows, macOS, Linux): easy for desktops, labs and testing, but with more overhead. Lesson: Hypervisors: Type 1 and Type 2
U
UDP: UDP is connectionless: no handshake, no acknowledgments, no resend. Lesson: TCP vs. UDP
UEFI: UEFI replaced legacy BIOS: mouse-driven menus, GPT disks over 2 TB, faster boot, Secure Boot. Lesson: BIOS vs. UEFI and boot options
Unbox properly: Unbox properly: big MFDs are heavy, so use two people or a lift; let a device that came in from the cold reach room temperature to avoid condensation; remove all shipping tape, locks and foam (toner/drum and scanner… Lesson: Unboxing and set-up location
Unmanaged: An unmanaged switch is plug-and-play with no settings: fine for a small office. Lesson: Switches: managed and unmanaged
Unusual noise: Unusual noise: grinding or rattling fans (bad bearing), clicking HDD, coil whine; find it with the case open (safely) and replace the part. Lesson: Overheating, random shutdowns, unusual noise
Up and down: Elasticity: resources scale up and down automatically with demand, e.g. Lesson: Elasticity and availability
USB: USB (Type-A) is the classic flat plug. Lesson: Wired connection methods
USB 2.0: USB 2.0 (High-Speed) = 480 Mbps, up to 5 m. Lesson: USB 2.0, USB 3.0 and Thunderbolt
USB 3.0: USB 3.0 (SuperSpeed, now called USB 3.2 Gen 1) = 5 Gbps, about 3 m, blue inserts on Type-A. Lesson: USB 2.0, USB 3.0 and Thunderbolt
USB boot: USB permissions can disable USB ports or USB boot so nobody boots another OS from a flash drive. Lesson: BIOS vs. UEFI and boot options
USB permissions: USB permissions can disable USB ports or USB boot so nobody boots another OS from a flash drive. Lesson: BIOS vs. UEFI and boot options
USB Power Delivery: USB-C is small, reversible, and can carry data, power (USB Power Delivery, up to 240 W) and video. Lesson: Wired connection methods
USB-C: USB-C is small, reversible, and can carry data, power (USB Power Delivery, up to 240 W) and video. Lesson: Wired connection methods
USB-to-serial adapter: Modern laptops use a USB-to-serial adapter. Lesson: Serial (RS-232)
User: Step 5: have the user confirm it works. Lesson: Using the steps well
User authentication: User authentication: sign in at the panel before copying, scanning or printing. Lesson: Security
UTM: UTM (unified threat management): one box with firewall, IPS, antivirus, content and URL filtering, VPN. Lesson: Internet appliances
UTP: UTP (unshielded) is standard in offices. Lesson: Twisted pair: UTP, STP and categories
V
VA: VA (vertical alignment) sits between: strong contrast/deep blacks, slower than TN. Lesson: LCD panel types: IPS, TN, VA
VDI: VDI (virtual desktop infrastructure) runs users' desktops as VMs in the data center or cloud. Lesson: Desktop virtualization (VDI)
Verify full system functionality: Verify full system functionality and, if applicable, implement preventive measures Lesson: The six steps, continued
Very dim: A failed inverter or CCFL gives a very dim image you can only see with a flashlight. Lesson: Backlights and the inverter
VGA: VGA: analog only, blue 15-pin 3-row DE-15 connector, image gets fuzzy at high resolutions. Lesson: Video cables
Video card: Video card (GPU): extra display outputs and 3D/compute power; often needs 6/8-pin or 16-pin PCIe power. Lesson: Expansion cards
Virtualization support: The host needs a CPU with virtualization support enabled (VT-x/AMD-V), plus enough RAM and cores for every VM at once. Lesson: VM requirements: storage, network, security
VLAN: A VLAN (virtual LAN) splits one physical switch into several separate logical networks (broadcast domains). Lesson: VLAN
VLANs: A managed switch can be configured: VLANs, port security, QoS, port mirroring, link aggregation, monitoring (SNMP). Lesson: Switches: managed and unmanaged
Voltage selector switch: Some older PSUs have a manual voltage selector switch: set 115 V and plug into 230 V and you can destroy the PSU. Lesson: Input voltage
VPN: A VPN (virtual private network) builds an encrypted tunnel across the internet. Lesson: VPN
VT-d/AMD-Vi: VT-d/AMD-Vi (IOMMU) lets a VM use a physical device directly. Lesson: Virtualization support
W
WAN: A WAN (wide area) spans regions or countries; the internet is the biggest WAN. Lesson: Network types: MAN, WAN, SAN
Web server: Web server: serves sites over HTTP/HTTPS. Lesson: File, print, mail, web, database, logs
Webcam: The webcam sits in the top bezel of the lid, usually with the microphones next to it. Lesson: Camera/webcam and microphone
Wi-Fi: With Wi-Fi on, the phone prefers known Wi-Fi networks over cellular. Lesson: Wi-Fi and hotspot on a phone
Wi-Fi analyzer: A Wi-Fi analyzer shows nearby networks, signal strength (dBm), channels and overlap so you can pick clear channels and find dead spots. Lesson: Finding and watching: toner probe, tap, Wi-Fi analyzer
Windows: Windows: the blue (or black) stop error screen with a stop code (e.g. Lesson: Proprietary crash screens
Wireless: Wireless: Wi-Fi (infrastructure mode on the company WLAN, or Wi-Fi Direct to a device) and sometimes Bluetooth. Lesson: Device connectivity
WISP: WISP (wireless ISP): fixed antennas aimed at a provider tower, common in rural areas, needs line of sight. Lesson: Satellite, cellular and WISP
WLAN: A WLAN is a wireless LAN (Wi-Fi). Lesson: Network types: LAN, WLAN, PAN
Wrong or corrupt driver: Garbled print (random characters, symbols, pages of code): wrong or corrupt driver (e.g. Lesson: Double/echo images and garbled print
WWAN: Some business laptops add a WWAN card for cellular data. Lesson: Wireless cards

Acronyms

Acronym	Stands for	What it means
AAA	Authentication, Authorization, and Accounting	The security trio: prove who you are, decide what you may do, and log what you did.
AAAA	IPv6 Address (DNS record)	DNS record that maps a host name to an IPv6 address.
AC	Alternating Current	The power from a wall outlet, which reverses direction many times a second. A PSU turns it into DC.
ACK	Acknowledgment	A TCP flag (and packet) that confirms data or a connection request was received.
ACL	Access Control List	An ordered list of allow and deny rules on a router, firewall or file, checked from the top down.
ADB	Android Debug Bridge	A developer tool that controls an Android device from a computer over USB or network. Leave it off on work phones.
ADF	Automatic Document Feeder	The tray on a printer or scanner that pulls sheets in one at a time so a stack can be copied or scanned without lifting the lid.
ADSL	Asymmetric Digital Subscriber Line	DSL with faster download than upload, over phone lines.
AHCI	Advanced Host Controller Interface	The standard mode for SATA drive controllers. Changing it from RAID or IDE after setup can stop Windows booting.
AI	Artificial Intelligence	Software that learns patterns from data to make predictions or generate text and images.
AIO	All-in-One	A single unit: an AIO liquid cooler (pump, tubes and radiator), or a PC built into its monitor.
AMD	Advanced Micro Devices, Inc.	Chip maker of Ryzen CPUs and Radeon GPUs, Intel's main rival for x86 processors.
AP	Access Point	A device that connects wireless clients to the wired network.
APIPA	Automatic Private Internet Protocol Addressing	A self-assigned 169.254.x.x address a device gives itself when no DHCP server answers. Seeing one means DHCP failed.
APK	Android Package Kit	The install file for an Android app. APKs from outside the Play Store (sideloading) can carry malware.
APN	Access Point Name	The phone setting that tells it which carrier gateway to use for mobile data. Wrong APN, no cellular data.
ARM	Advanced RISC (Reduced Instruction Set Computer) Machine	A CPU design with a small, simple instruction set that sips power: used in phones, tablets and Apple silicon Macs.
ARP	Address Resolution Protocol	Finds the MAC address that goes with an IPv4 address on the local network. Fake replies enable ARP poisoning.
ATX	Advanced Technology eXtended	The standard size and layout for desktop motherboards, cases and power supplies (full ATX boards are 12 x 9.6 in).
BCD	Boot Configuration Data	The Windows database that tells the boot manager which OS to start and how; repaired with bootrec or bcdedit.
BIOS	Basic Input/Output System	Older firmware that tests the hardware and starts the operating system. UEFI has replaced it on modern PCs.
BLE	Bluetooth Low Energy	A low-power Bluetooth mode for sensors, beacons and wearables.
BNC	Bayonet Neill-Concelman	A twist-lock bayonet connector for coaxial cable.
CA	Certificate Authority	A trusted organization that checks identities and signs digital certificates.
CAD	Computer-Aided Design	Software for technical drawings and 3D models; it needs a strong workstation and GPU.
CCFL	Cold Cathode Fluorescent Lamp	The old tube backlight in LCD screens. It needs an inverter; when it fails the image goes very dim.
CCMP	Counter Mode with CBC-MAC Protocol	The AES-based encryption and integrity protocol used by WPA2.
CCTV	Closed-circuit Television	Video cameras that record to a private system for watching and evidence.
CD	Compact Disc	An optical disc holding about 700 MB.
CEO	Chief Executive Officer	The top executive of a company.
CFO	Chief Financial Officer	The executive in charge of the company's money; a favorite name for attackers to fake in BEC emails.
CIDR	Classless Inter-domain Routing	Writes a network as an address plus a prefix length, like 192.168.1.0/24, instead of fixed classes.
CIFS	Common Internet File System	An older Microsoft version (dialect) of SMB file and printer sharing.
CMOS	Complementary Metal-Oxide Semiconductor	The small battery-backed memory that keeps firmware settings and the clock. A dead CMOS battery resets the time.
CNAME	Canonical Name	DNS record that makes one name an alias of another name.
CPU	Central Processing Unit	The main processor chip that runs program instructions.
CRT	Cathode Ray Tube	The old, deep glass-tube monitor. It holds dangerous voltage even when unplugged.
CSM	Compatibility Support Module	A UEFI option that boots the old BIOS way (legacy boot). It turns off Secure Boot.
CVV	Card Verification Value	The 3- or 4-digit security code on a payment card. PCI DSS forbids storing it after the payment.
DB-9	D-subminiature (D-sub) serial connector, 9 pins	The 9-pin D-shaped serial (RS-232) connector, still seen on console cables and older devices.
DC	Direct Current	Steady one-direction power, like a battery's; a PSU supplies 12 V, 5 V and 3.3 V DC.
DDR	Double Data Rate	The family of PC memory that moves data twice per clock tick. DDR4 and DDR5 modules are keyed differently.
DDR3	Double Data Rate 3	An older generation of PC memory (1.5 V). Doesn't fit DDR4 or DDR5 slots.
DDR4	Double Data Rate 4	The PC memory generation before DDR5: 288 pins, 1.2 V. Not interchangeable with DDR5.
DDR5	Double Data Rate 5	Current PC memory: faster than DDR4, 1.1 V, with power management on the module. Doesn't fit DDR4 slots.
DFS	Dynamic Frequency Selection	5 GHz Wi-Fi rule: access points listen for radar and move off a channel when they hear it.
DHCP	Dynamic Host Configuration Protocol	Hands devices an IP address, subnet mask, gateway and DNS server automatically (Discover, Offer, Request, Acknowledge).
DIMM	Dual Inline Memory Module	The full-size memory module used in desktop PCs and servers.
DISM	Deployment Image Servicing and Management	A Windows command-line tool that repairs the system image (run it before SFC when SFC can't fix files).
DKIM	DomainKeys Identified Mail	Signs outgoing email so receiving servers can check, with a key in DNS, that it came from the domain unchanged.
DLL	Dynamic Link Library	A Windows file of shared code that programs load; attackers may plant or inject a malicious one.
DMARC	Domain-based Message Authentication, Reporting, and Conformance	A DNS policy telling receivers what to do with mail that fails SPF and DKIM checks, and where to send reports.
DMZ	Demilitarized Zone	A separate network zone for public-facing servers, between the internet and the internal network. Also called a screened subnet.
DNS	Domain Name System	The internet's phone book: it turns names like example.com into IP addresses.
DOCSIS	Data Over Cable Service Interface Specification	The standard that carries internet over cable TV coax to a cable modem.
DORA	Discover, Offer, Request, Acknowledge	The four DHCP steps a client and server go through to hand out an IP address.
DP	DisplayPort	A digital video connector for monitors; it can daisy-chain screens and runs over USB-C (Alt Mode).
DRAM	Dynamic Random-Access Memory	The main memory chips in a PC; they must be refreshed constantly and lose data without power.
DSL	Digital Subscriber Line	Internet service carried over ordinary telephone lines.
DVD	Digital Versatile Disc	An optical disc holding 4.7 GB (single layer) or 8.5 GB (dual layer).
DVI	Digital Visual Interface	An older digital (and on some versions analog) video connector, before HDMI and DisplayPort took over.
ECC	Error-Correcting Code	Memory that finds and fixes single-bit errors on the fly; used in servers and workstations.
EFI	Extensible Firmware Interface	Early name for UEFI. The EFI system partition holds the boot loaders on GPT disks.
EMI	Electromagnetic Interference	Electrical noise from motors, lights or power cables that corrupts signals on nearby copper cable.
EPS	Entry-Level Power Supply (EPS12V)	The 4- or 8-pin 12 V power connector for the CPU, near the socket.
EPT	Extended Page Tables	Intel's hardware help for VM memory (a form of SLAT), which speeds up virtual machines.
eSATA	External Serial Advanced Technology Attachment	An external SATA port and cable for plugging in outside drives at SATA speed.
EXPO	Extended Profiles for Overclocking	AMD's memory profile setting that runs RAM at its rated speed (like Intel XMP).
FCC	Federal Communications Commission	The US agency that regulates radio use, including Wi-Fi channels and power.
FTP	File Transfer Protocol	Transfers files on ports 20 and 21 with no encryption; logins travel in clear text.
GDPR	General Data Protection Regulation	The EU law that protects the personal data of people in the EU, with heavy fines for breaking it.
GPL	GNU General Public License	An open-source license: you may use and change the code, but shared changes must stay open source.
GPO	Group Policy Object	A bundle of Windows settings pushed from Active Directory to users and computers.
GPS	Global Positioning System	Satellite system that tells a device where it is; used for maps, tracking and finding lost phones.
GPU	Graphics Processing Unit	The processor that draws graphics; also used for heavy parallel math like AI.
GUI	Graphical User Interface	Windows, icons and menus you click, instead of typed commands.
HD	High Definition	Video at 720p or 1080p resolution.
HDD	Hard Disk Drive	A disk drive with spinning platters and a moving head: cheap per gigabyte, slower than an SSD.
HDMI	High-Definition Multimedia Interface	The common digital cable for video and audio together, for TVs, monitors and projectors.
HFS	Hierarchical File System	Apple's older Mac file system (HFS+), replaced by APFS.
HIPAA	Health Insurance Portability and Accountability Act	The US law that protects patients' health information (PHI).
HR	Human Resources	The department that hires people, onboards and offboards them, and keeps staff records.
HSM	Hardware Security Module	A tamper-resistant hardware device that creates, stores and uses crypto keys so they never leave it.
HTTP	Hypertext Transfer Protocol	The protocol for web pages, port 80. Not encrypted.
HTTPS	Hypertext Transfer Protocol Secure	HTTP encrypted with TLS, port 443: the padlock in the browser.
IaaS	Infrastructure as a Service	Rent virtual servers, storage and networks from a cloud; you still manage the OS and everything above it.
ICMP	Internet Control Message Protocol	Carries network errors and tests, such as ping (echo) and the messages traceroute relies on.
ID	Identifier	A name or number that identifies something, like a user ID or badge ID.
IDC	Insulation Displacement Connector	The slots on a punch-down block or keystone jack that cut through wire insulation to make contact.
IEEE	Institute of Electrical and Electronics Engineers	The body that writes networking standards such as 802.3 (Ethernet) and 802.11 (Wi-Fi).
IIS	Internet Information Services	Microsoft's web server for Windows.
IMAP	Internet Message Access Protocol	Reads email while keeping it on the server, synced across devices. Port 143, or 993 with TLS.
IMAPS	Internet Message Access Protocol Secure	IMAP email over TLS, port 993.
IMSI	International Mobile Subscriber Identity	The unique number on a SIM that identifies a subscriber to the cellular network.
IOMMU	Input-Output Memory Management Unit	CPU feature (Intel VT-d, AMD-Vi) that lets a VM safely use a physical device directly.
IOPS	Input/Output Operations Per Second	How many read and write operations a drive can do per second; a key storage speed measure.
IoT	Internet of Things	Everyday devices with network connections, such as cameras, thermostats and smart speakers.
IP	Internet Protocol	The protocol that addresses and routes packets between networks.
IPS	In-Plane Switching	An LCD panel type with wide viewing angles and good color; slower response than TN.
IPv4	Internet Protocol version 4	The original internet address: 32 bits, written like 192.168.1.10.
IPv6	Internet Protocol version 6	The newer internet address: 128 bits, written in hex like 2001:db8::1.
IR	Infrared	Light just beyond what eyes can see; IR cameras do face sign-in, and IR is used by remote controls.
IRC	Internet Relay Chat	An old text chat system (often port 6667); some botnets still use it to take orders.
ISM	Industrial, Scientific and Medical	Radio bands open to unlicensed use, such as 2.4 GHz shared by Wi-Fi, Bluetooth and microwave ovens.
ISP	Internet Service Provider	The company that connects you to the internet.
IT	Information Technology	Computers, networks and the people who run them.
ITX	Information Technology eXtended	Small motherboard sizes for compact PCs; mini-ITX boards are 6.7 x 6.7 in.
JIT	Just-in-Time	Admin rights granted only when needed and removed automatically afterwards.
KB	Knowledge Base	A library of help articles and fixes; Microsoft also numbers its updates as KB articles.
KVM	Keyboard-Video-Mouse	A switch that lets one keyboard, monitor and mouse control several computers.
LAN	Local Area Network	The network in one building or site.
LC	Lucent Connector	A small square fiber connector with a push-and-click latch, common on SFP modules.
LCD	Liquid Crystal Display	A flat-panel screen of liquid crystals lit from behind by a backlight.
LDAP	Lightweight Directory Access Protocol	The protocol for reading and searching a directory such as Active Directory. Port 389; LDAPS uses 636.
LED	Light-Emitting Diode	A light-emitting diode: used as status lights and as the backlight in most LCD screens.
LGA	Land Grid Array	A CPU socket where the pins are in the socket on the motherboard, not on the CPU.
LPDDR	Low-Power Double Data Rate	Power-saving memory soldered onto phone and thin-laptop boards; it can't be upgraded.
LTE	Long-Term Evolution	The 4G cellular data standard.
MAC	Media Access Control	The 48-bit hardware address burned into a network interface, written like 00:1A:2B:3C:4D:5E.
MAN	Metropolitan Area Network	A network that covers a city or a campus.
MDM	Mobile Device Management	Central control of phones and tablets: enforce passcodes, push apps and settings, and wipe lost devices.
MFD	Multifunction Device	One machine that prints, scans, copies and often faxes.
MIMO	Multiple Input, Multiple Output	Several antennas sending and receiving at once to carry more data.
mSATA	Mini-Serial Advanced Technology Attachment	A small SATA SSD card used in older laptops before M.2.
MSP	Managed Service Provider	An outside company that runs your IT for a monthly fee.
MST	Multi-Stream Transport	A DisplayPort feature for running several monitors from one port (daisy-chaining).
MTBF	Mean Time Between Failures	The average time a repairable device runs between failures.
MX	Mail Exchanger (DNS record)	DNS record that names the mail server for a domain.
NAS	Network-attached Storage	A box on the network that shares files over SMB or NFS.
NAT	Network Address Translation	Swaps private internal IP addresses for a public one as traffic leaves the network.
NetBIOS	Network Basic Input/Output System	An old Windows naming and sharing service (ports 137 to 139), still found on some networks.
NFC	Near-Field Communication	Very short-range wireless (a few centimeters) used for tap-to-pay and pairing.
NIC	Network Interface Card	The hardware that connects a computer to a network.
NTP	Network Time Protocol	Keeps device clocks in sync over the network (UDP 123), which logs and Kerberos rely on.
NVMe	Non-Volatile Memory Express	A fast protocol for SSDs over PCIe lanes, much quicker than SATA. Usually an M.2 stick.
NVR	Network Video Recorder	A box that records video from IP cameras.
OEM	Original Equipment Manufacturer	The company that made the device or part; the right place to get its drivers and firmware.
OLED	Organic Light-Emitting Diode	A screen where every pixel makes its own light: true blacks, no backlight. Can burn in.
ONT	Optical Network Terminal	The box where the provider's fiber ends at a home or business, turning light into Ethernet.
OS	Operating System	The core software that runs a computer, such as Windows, macOS, Linux, Android or iOS.
OSHA	Occupational Safety and Health Administration	The US agency that sets workplace safety rules.
OU	Organizational Unit	A folder inside an Active Directory domain for users and computers; Group Policy can be linked to it.
OUI	Organizationally Unique Identifier	The first half (24 bits) of a MAC address, which identifies the manufacturer.
PaaS	Platform as a Service	A cloud platform to run your code on; the provider manages the servers, OS and runtime.
PAN	Personal Area Network	A tiny personal network around one person, like Bluetooth earbuds and a phone.
PC	Personal Computer	A personal computer: a desktop or laptop.
PCI	Peripheral Component Interconnect	An older expansion slot standard for desktop cards, replaced by PCIe.
PCIe	Peripheral Component Interconnect Express	The fast expansion bus for graphics cards, NVMe drives and more, in lanes (x1, x4, x16).
PCL	Printer Command Language	HP's printer language, common for everyday office printing (PostScript is the other).
PDF	Portable Document Format	A file format that looks the same on every device; can hide malicious links or scripts.
PGA	Pin Grid Array	A CPU with the pins on the chip itself, which fit holes in the socket (older AMD).
PID	Process ID	The number the operating system gives each running program.
PMIC	Power Management Integrated Circuit	A chip that manages power; DDR5 memory has its own on each module.
PoE	Power over Ethernet	Sends power over the Ethernet cable, so cameras, phones and access points need no separate plug.
POP	Post Office Protocol	Downloads email to one device, usually removing it from the server. POP3 uses port 110, or 995 with TLS.
POP3	Post Office Protocol version 3	Downloads email to one device, usually removing it from the server. Port 110, or 995 with TLS.
POP3S	Post Office Protocol 3 Secure	POP3 email over TLS, port 995.
POST	Power-On Self-Test	The hardware self-test a PC runs at power-on; beeps or codes point to the failed part.
PPI	Pixels per Inch	How densely a screen packs its pixels; more PPI looks sharper.
PSK	Pre-shared Key	A shared password everyone types to join a network, as in WPA2-Personal.
PSU	Power Supply Unit	Turns wall AC power into the DC voltages a computer's parts need.
PTT	Platform Trust Technology	Intel's TPM built into the CPU firmware (AMD calls theirs fTPM); turn it on in UEFI for Windows 11.
PVC	Polyvinyl Chloride	Ordinary cable jacket plastic. It gives off toxic smoke in a fire, so use plenum cable in air spaces.
PWM	Pulse-Width Modulation	How 4-pin fan headers control fan speed, by switching power on and off very fast.
PXE	Preboot Execution Environment	Lets a PC boot from the network to install or load an OS from a server.
QEMU	Quick Emulator	An open-source emulator and virtualizer, often paired with KVM on Linux.
QoS	Quality of Service	Giving important traffic, such as voice and video, priority over other traffic.
QR	Quick Response	A square barcode phones can scan; a fake one can lead to a phishing site (quishing).
RAID	Redundant Array of Independent (or Inexpensive) Disks	Combines several disks for speed, redundancy or both (RAID 0, 1, 5, 6, 10). Not a backup.
RAM	Random-Access Memory	Fast working memory that is wiped when the power goes off.
RD	Remote Desktop	Microsoft's remote desktop service; an RD Gateway lets users reach it safely through HTTPS.
RDP	Remote Desktop Protocol	Microsoft's remote desktop protocol, TCP port 3389. Don't expose it to the internet.
RFID	Radio-Frequency Identification	Reads tags by radio without line of sight, as in badges, inventory tags and toll passes.
RHEL	Red Hat Enterprise Linux	A widely used commercial Linux for servers; it uses dnf/yum packages and XFS by default.
RISC	Reduced Instruction Set Computer	A CPU design with a small set of simple instructions, like ARM; efficient on power.
RJ11	Registered Jack 11	The small phone-line connector (usually 2 or 4 wires).
RJ45	Registered Jack 45	The 8-pin connector on Ethernet cables.
RPM	Revolutions per Minute	How fast a hard drive's platters or a fan spins, such as 7200 RPM.
RTC	Real-Time Clock	The battery-backed clock chip that keeps time while the computer is off.
S.M.A.R.T.	Self-Monitoring, Analysis, and Reporting Technology	A drive's built-in health monitoring that can warn you before it fails.
SaaS	Software as a Service	Finished software you use over the internet, like webmail; the provider runs everything.
SAE	Simultaneous Authentication of Equals	The WPA3 password handshake (Dragonfly), which stops offline password guessing.
SAN	Storage Area Network	A dedicated network that gives servers block-level storage, as if the disks were local.
SAS	Serial Attached SCSI	A fast, reliable serial drive interface for servers, using SCSI commands.
SATA	Serial Advanced Technology Attachment	The common cable interface for internal hard drives, SSDs and optical drives.
SC	Subscriber Connector	A square fiber connector that pushes in and pulls out.
SCADA	Supervisory Control and Data Acquisition	Systems that monitor and control industrial processes, often spread over large areas like pipelines and grids.
SCP	Secure Copy Protocol	Copies files over SSH (port 22).
SCSI	Small Computer System Interface	An older family of standards for connecting drives; its commands live on in SAS and iSCSI.
SD	Secure Digital	The common memory card format for cameras and devices (SDHC and SDXC are the larger versions).
SDHC	Secure Digital High Capacity	SD cards from over 2 GB up to 32 GB.
SDS	Safety Data Sheet	The safety sheet for a product: hazards, safe handling, disposal and first aid.
SDXC	Secure Digital Extended Capacity	SD cards from over 32 GB up to 2 TB.
SFC	System File Checker	The Windows command (sfc /scannow) that checks protected system files and repairs damaged ones.
SFP	Small Form-factor Pluggable	A small hot-swappable module that gives a switch port fiber or copper at up to 1 Gb.
SHA	Secure Hash Algorithm	A family of hash functions; SHA-256 is common today, SHA-1 is broken.
SID	Security Identifier	The unique number Windows gives each user, group and computer; permissions use it, not the name.
SIM	Subscriber Identity Module	The small card (or eSIM) that ties a phone to a cellular account and number.
SLAT	Second Level Address Translation	CPU help for virtual machine memory (Intel EPT, AMD RVI); needed by some hypervisors.
SMB	Server Message Block	Windows file and printer sharing protocol, TCP port 445. Turn off the old SMBv1.
SMT	Simultaneous Multithreading	Lets one CPU core run two threads at once (Intel calls it Hyper-Threading).
SMTP	Simple Mail Transfer Protocol	Sends email between mail servers (port 25) and from apps to their server (587).
SNMP	Simple Network Management Protocol	Lets a monitoring system read and change device settings and receive alerts (traps). UDP 161 and 162.
SODIMM	Small Outline Dual Inline Memory Module	The smaller memory module used in laptops and small PCs.
SOHO	Small Office/Home Office	A small office or home office, usually with one all-in-one router.
SPF	Sender Policy Framework	A DNS TXT record listing which servers may send email for a domain.
SQLi	SQL Injection	Typing database commands into an app's input so the database runs them. Stopped by parameterized queries.
SSD	Solid-State Drive	Storage on flash chips, with no moving parts: much faster than a spinning hard drive.
SSH	Secure Shell	An encrypted remote command line, TCP port 22. Replaces Telnet.
SSID	Service Set Identifier	The name of a Wi-Fi network.
SSN	Social Security Number	The US government ID number: highly sensitive PII.
ST	Straight Tip	A round fiber connector with a twist-lock bayonet, found on older installs.
STP	Spanning Tree Protocol	Switches block redundant links so frames can't loop forever.
SVM	Secure Virtual Machine	AMD's CPU virtualization feature (AMD-V); turn it on in UEFI to run VMs.
SYN	Synchronize	The TCP flag that opens a connection: the first step of the three-way handshake.
TCP	Transmission Control Protocol	Reliable, connection-based delivery: a three-way handshake, then data is acknowledged and resent if lost.
TDP	Thermal Design Power	How much heat, in watts, a CPU or GPU is built to give off; used to size coolers and power supplies.
TLS	Transport Layer Security	Encrypts and authenticates connections, such as HTTPS. Use TLS 1.2 or 1.3.
TN	Twisted Nematic	The cheapest LCD panel type: very fast, but colors shift when viewed from an angle.
TPM	Trusted Platform Module	A security chip on the motherboard that stores keys and checks that the boot hasn't been tampered with.
TV	Television	A television; cable TV and modems use coax with F-type connectors.
TXT	Text record	DNS record that holds text; SPF, DKIM, DMARC and domain checks are published this way.
UDP	User Datagram Protocol	Fast, connectionless delivery with no handshake or resending; used for DNS, VoIP and streaming.
UEFI	Unified Extensible Firmware Interface	Modern PC firmware that replaced BIOS: GPT boot disks, Secure Boot and a graphical setup screen.
UHD	Ultra High Definition	Video at 3840 x 2160 (4K) resolution.
UID	User ID	The number Linux uses for each user account; UID 0 is root.
UNC	Universal Naming Convention	The Windows path to a network share, written \\server\share.
USB	Universal Serial Bus	The common plug for keyboards, drives, phones and chargers.
UTM	Unified Threat Management	One box that combines firewall, IPS, antivirus, web filtering and more.
UTP	Unshielded Twisted Pair	Ordinary Ethernet cable: twisted copper pairs with no shield.
VA	Vertical Alignment	An LCD panel type with deep blacks and high contrast, between TN and IPS for viewing angles.
VAC	Volts of Alternating Current	AC voltage, such as 110-120 VAC in North America and 220-240 VAC in Europe.
VCSEL	Vertical-Cavity Surface-Emitting Laser	A cheap laser used in multimode fiber transceivers for short runs.
VDC	Volts of Direct Current	DC voltage, such as the 12, 5 and 3.3 VDC a PC power supply provides.
VDI	Virtual Desktop Infrastructure	Desktops that run as virtual machines in a data center and are reached over the network.
VGA	Video Graphics Array	An old analog video connector with 15 pins in three rows, usually blue.
VLAN	Virtual Local Area Network	Splits one physical switch into separate logical networks.
VM	Virtual Machine	A software computer running on a hypervisor, with its own OS, sharing the real hardware.
VoIP	Voice over Internet Protocol	Phone calls carried over IP networks instead of phone lines.
VPN	Virtual Private Network	An encrypted tunnel across an untrusted network, such as the internet.
VRAM	Video Random-Access Memory	Memory on the graphics card used for images and textures.
VT	Virtualization Technology	Intel's CPU virtualization feature (VT-x); turn it on in UEFI to run VMs.
WAN	Wide Area Network	A network that links sites across long distances.
WAP	Wireless Access Point	A device that connects wireless clients to the wired network.
WEP	Wired Equivalent Privacy	The original Wi-Fi encryption, broken within minutes. Never use it.
WHEA	Windows Hardware Error Architecture	How Windows reports hardware errors; a WHEA stop error points to failing hardware or overclocking.
WinPE	Windows Preinstallation Environment	A small Windows that boots from USB or the network to install or repair Windows.
WinRE	Windows Recovery Environment	The Windows repair menu: Startup Repair, System Restore, Command Prompt and reset.
WISP	Wireless Internet Service Provider	An internet provider that delivers service by fixed wireless links.
WLAN	Wireless Local Area Network	A local network over Wi-Fi.
WPA2	Wi-Fi Protected Access 2	Wi-Fi security with AES (CCMP). Personal mode uses a shared password; Enterprise uses 802.1X logins.
WPA3	Wi-Fi Protected Access 3	The newest Wi-Fi security: SAE stops offline password guessing, with stronger encryption options.
WPS	Wi-Fi Protected Setup	Push-button or PIN Wi-Fi setup. The PIN can be brute-forced, so turn it off.
WWAN	Wireless Wide Area Network	Wide-area wireless data, such as a cellular connection.
XML	Extensible Markup Language	A text format that marks up data with tags; used by SAML and SOAP.
XMP	Extreme Memory Profile	Intel's memory profile setting that runs RAM at its rated speed instead of a slow default.
ZIF	Zero Insertion Force	A connector with a flip-up latch so ribbon cables (or old CPUs) go in without pressure.

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