A
Ampere / Amp
Unit of electrical current. Context matters: the letter A can also simply be an answer label.
A+ / IT foundations reference
FamilyPD A+ / IT Foundations Glossary
Search the abbreviations and basic IT terms used across the missions. Some important words—such as hardware, software, Linux, macOS, Windows, and iOS—are not acronyms, but you still need to recognize what they mean and where they fit.
Notebook rule: Do not copy only a definition. Add the useful clue that helps you recognize the term in a real computer or scenario. Example: DIMM = Dual Inline Memory Module → “full-size removable desktop RAM module.”
Study coverage: This reference also includes foundational terms used across the current A+ course presentations, including hardware, cables, memory, networking, operating systems, mobile devices, virtualization, security, and troubleshooting.
Quick distinction: This page combines acronyms/initialisms (CPU, I/O, OEM), platform or product names (Windows, macOS, iOS, Android), and basic IT terminology (hardware, software, driver, firmware). Everything is listed together in alphabetical order so it works as one practical study reference.
AC
Alternating Current
Electrical power that periodically reverses direction; wall power is AC.
ACL
Access Control List
A list of rules or permissions that controls access to a resource or filters traffic, depending on context.
Android
Mobile operating system
A mobile operating system used by many phones, tablets, and other devices. Android is not an acronym.
AP
Access Point
A device that provides wireless network access and commonly bridges wireless clients to a wired LAN.
APFS
Apple File System
A file system used by modern Apple operating systems and storage devices.
API
Application Programming Interface
A defined way for software components or services to communicate with each other.
APIPA
Automatic Private IP Addressing
An IPv4 self-assigned address in the 169.254.0.0/16 range used when a client cannot obtain an address from DHCP.
App
Application
Software designed to help a user perform a task. “App” is short for application.
ARM
Advanced RISC Machines / ARM architecture
A processor architecture family widely used in phones, tablets, single-board computers, and other power-efficient systems.
ARM64
64-bit Arm Architecture
64-bit software/processor architecture label used by many Arm-based systems.
ATX
Advanced Technology eXtended
A common desktop motherboard and case form-factor standard that also influences mounting and power conventions.
Audio
Sound input/output
Computer sound functions, including speakers, headphones, microphones, audio ports, and sound hardware.
BIOS
Basic Input/Output System
Legacy firmware term; often used generically, but modern PCs commonly use UEFI.
Bluetooth
Wireless technology
Short-range wireless communication commonly used for keyboards, mice, headphones, phones, and other peripherals.
Browser
Web browser
Software used to access and interact with websites and web applications.
BSOD
Blue Screen of Death
Informal name for a Windows stop/error screen caused by a serious system failure.
Cable
Physical connection
A wired connection used to carry power, data, signals, or a combination, depending on the cable type.
Cache
High-speed temporary storage
Fast storage that keeps frequently needed data close to the processor or application for quicker access.
CLI
Command-Line Interface
Text-based interface where users enter commands.
CMOS
Complementary Metal-Oxide-Semiconductor
A semiconductor technology term. In PC support, 'CMOS' is also commonly used historically for firmware settings/RTC memory maintained by the coin-cell battery.
Coaxial
Coaxial cable
A cable with a center conductor, insulation, shielding, and outer jacket; used in cable broadband and some legacy networking/video systems.
COM
Communications Port
Windows name for serial communication ports, historically associated with RS-232.
Connector
Physical interface
A plug, socket, port, or header that joins components or cables. Shape and keying help prevent incorrect connections.
CPU
Central Processing Unit
Executes program instructions and performs calculations.
Data Bus
Data communication pathway
A set of electrical pathways/signals used to move data between components. Bus width and speed affect how much data can be transferred.
DB-25
25-position D-sub connector
A connector used historically for serial and parallel interfaces, depending on implementation.
DB-9
9-position D-sub connector
A connector commonly associated with RS-232 serial communication on PCs.
DC
Direct Current
Electrical current that flows in one direction. Computer components operate on regulated DC power.
DDR
Double Data Rate
Family of synchronous DRAM technologies; generations include DDR3, DDR4, and DDR5.
DDR2
Double Data Rate 2 SDRAM
An older DDR memory generation; not physically interchangeable with other DDR generations.
DDR3
Double Data Rate 3 SDRAM
An older DDR memory generation with a generation-specific notch, voltage, and signaling.
DDR4
Double Data Rate 4 SDRAM
A DDR memory generation widely used in PCs; not interchangeable with DDR3 or DDR5.
DDR5
Double Data Rate 5 SDRAM
A newer DDR memory generation with higher data rates and a different physical/electrical design than DDR4.
DHCP
Dynamic Host Configuration Protocol
Automatically provides clients with IP configuration information.
DIMM
Dual Inline Memory Module
Full-size removable RAM module common in desktop computers.
DisplayPort
Digital display interface
A digital audio/video interface commonly used with monitors. It can support high resolutions, high refresh rates, and features such as multi-display daisy chaining when supported.
DNS
Domain Name System
Translates names such as websites into IP addresses.
DP
DisplayPort
Digital display interface supporting audio/video and high resolutions/refresh rates.
Driver
Device driver
Software that allows an operating system to communicate correctly with a hardware device.
DVI
Digital Visual Interface
Older display interface that can carry digital video; some variants support analog.
ECC
Error-Correcting Code
Memory technology that can detect and correct certain memory errors; common in systems where reliability is especially important.
EMM
Enterprise Mobility Management
Tools and policies used by organizations to manage mobile devices, applications, data, and security.
EOL
End of Life
A stage when a product has reached the end of its lifecycle; availability, updates, or support may be limited or ended.
EOSL
End of Service Life
A point after which a vendor no longer provides normal service/support for a product.
eSATA
External SATA
External version of SATA; legacy compared with modern USB/Thunderbolt storage connections.
ESD
Electrostatic Discharge
A sudden transfer of static electricity that can damage electronic components.
Ethernet
Wired networking technology
A common wired LAN technology used to connect computers and network equipment.
FAT
File Allocation Table
A family of file systems used on storage media; variants include FAT32.
FFC
Flat Flexible Cable
Thin flexible cable used for compact internal connections; Pi 5 exposes PCIe through an FFC connector.
Firmware
Low-level device software
Software stored on hardware that helps control or initialize a device. UEFI/BIOS is a common PC example.
FQDN
Fully Qualified Domain Name
The complete domain name identifying a host within the DNS hierarchy.
FTP
File Transfer Protocol
A traditional protocol for transferring files. Standard FTP does not encrypt credentials or data.
GB
Gigabyte
A unit used to describe data/storage capacity. Context determines whether decimal or binary-based measurements are being used.
GHz
Gigahertz
One billion cycles per second; commonly used to describe processor or radio clock/frequency rates.
GPIO
General-Purpose Input/Output
Programmable pins on boards such as Raspberry Pi used to interface with electronics.
GPT
GUID Partition Table
A modern disk partitioning scheme commonly used with UEFI systems and large storage devices.
GPU
Graphics Processing Unit
Processes graphics and highly parallel workloads.
GUI
Graphical User Interface
Visual interface using windows, icons, menus, and pointers/touch.
Hardware
Physical computer components
The parts you can physically touch, such as a motherboard, CPU, RAM, storage drive, keyboard, or cable.
HDD
Hard Disk Drive
Magnetic persistent storage with moving mechanical parts.
HDMI
High-Definition Multimedia Interface
Digital audio/video interface used with displays.
HP
Hewlett-Packard
A manufacturer name you may see on computers and peripherals. It is not a hardware standard or compatibility specification.
HTTP
Hypertext Transfer Protocol
Web application protocol; unencrypted HTTP does not provide TLS protection.
HTTPS
Hypertext Transfer Protocol Secure
HTTP protected by TLS.
IDE
Integrated Drive Electronics
A legacy parallel storage interface commonly associated with PATA.
IEEE
Institute of Electrical and Electronics Engineers
A standards organization associated with technologies such as the IEEE 802 networking standards.
IMAP
Internet Message Access Protocol
An email access protocol that commonly keeps messages on the server and synchronizes mailbox state across devices.
I/O
Input / Output
How data enters or leaves a computer or component. Keyboards and microphones provide input; displays and speakers provide output; many ports handle both.
iOS
Mobile operating system
An operating system used on iPhone devices. It manages hardware, apps, files, networking, security, and user interaction.
IP
Internet Protocol
Provides logical addressing and routing between networks.
IPS
In-Plane Switching
LCD panel type known for viewing angles and color reproduction.
IPv4
Internet Protocol version 4
The widely used IP version with 32-bit addresses, commonly written in dotted-decimal notation.
IPv6
Internet Protocol version 6
An IP version with 128-bit addresses designed to provide a much larger address space and other improvements.
ISP
Internet Service Provider
An organization that provides Internet connectivity.
IT
Information Technology
The field involving computers, networks, software, data, support, and related technology systems.
LAN
Local Area Network
Network covering a limited local area such as a home, school, or office.
LCD
Liquid Crystal Display
Flat-panel display technology that uses liquid crystals and a backlight.
LED
Light-Emitting Diode
An electronic component that emits light; used for indicators, displays, lighting, and diagnostics.
Legacy
Older technology still encountered
Hardware, software, interfaces, or standards from an earlier generation that may still be in use but have been replaced or superseded by newer approaches.
LGA
Land Grid Array
A CPU socket/package style in which contact lands are used instead of pins on the processor package.
Lightning
Mobile device connector
A proprietary connector used on some older Apple mobile devices and accessories.
Linux
Operating system family
A family of open-source operating systems built around the Linux kernel. Linux is not an acronym. Explore Linux families, package managers, commands, cybersecurity-focused distributions, hardware uses, and installation options.
LLC
Logical Link Control
The upper sublayer of the OSI Data Link layer in IEEE 802 networking concepts.
LPDDR
Low-Power Double Data Rate
Low-power memory commonly used in mobile and integrated devices; Pi 5 uses LPDDR4X.
M.2
M.2 Form Factor
Compact card form factor often used for NVMe or SATA SSDs and some wireless cards; not itself an acronym.
MAC
Media Access Control
In networking, a MAC address is a link-layer identifier associated with a network interface. Do not confuse MAC with Mac computers or macOS.
macOS
Desktop operating system
An operating system used on Mac computers. macOS is a product/platform name, not an acronym.
MDM
Mobile Device Management
Technology used to configure, secure, monitor, and manage mobile devices.
Modern
Current-generation technology
A relative term for technology currently in common use or support. What counts as modern changes over time, so identify the specific standard/version in technical work.
Motherboard
Main system board
The primary circuit board that connects the CPU, memory, storage, expansion, power, and I/O components in a PC.
MU-MIMO
Multi-User Multiple Input Multiple Output
A wireless technology that allows an access point to communicate with multiple clients more efficiently.
NAS
Network-Attached Storage
Storage connected to a network so files or storage services can be accessed by network clients.
NFC
Near Field Communication
Very short-range wireless communication used for functions such as tap-to-pay, pairing, and tags.
NIC
Network Interface Card / Controller
Hardware interface that connects a device to a network.
NTP
Network Time Protocol
A protocol used to synchronize clocks across networked systems; commonly associated with UDP port 123.
NVMe
Non-Volatile Memory Express
Protocol designed for high-speed solid-state storage over PCIe.
OEM
Original Equipment Manufacturer
A company that manufactures or supplies a complete system or components for sale under its own or another company’s name. OEM systems may use standard or proprietary parts.
OLED
Organic Light-Emitting Diode
Display technology where pixels emit their own light.
Operating System
OS
Core software that manages hardware and provides services for applications. Examples include Windows, macOS, Linux, iOS, and Android.
OS
Operating System
Core software that manages hardware and provides services for applications. Examples include Windows, macOS, Linux, iOS, and Android.
Parallel
Multiple bits/signals at once
A communication method that transfers multiple bits simultaneously across multiple signal lines. Older parallel interfaces are common examples of legacy PC technology.
Parallel Bus
Parallel data pathway
A bus that carries multiple data bits simultaneously across multiple lines; common in older computer architectures/interfaces.
PATA
Parallel Advanced Technology Attachment
A legacy parallel interface for connecting storage devices; largely replaced by SATA.
PC
Personal Computer
A general-purpose computer designed primarily for individual use; may refer to desktops, laptops, and similar systems depending on context.
PCI
Peripheral Component Interconnect
Older/legacy expansion-bus standard that is physically different from PCIe.
PCIe
Peripheral Component Interconnect Express
High-speed expansion interface used for GPUs, NICs, NVMe storage, and other devices.
PDU
Protocol Data Unit
Networking term for the unit of information associated with a layer. Examples include data, TCP segment/UDP datagram, packet, frame, and bits. In power/datacenter contexts, PDU can also mean Power Distribution Unit.
Peripheral
External or attached device
A device connected to a computer for input, output, storage, communication, or another function, such as a keyboard, mouse, printer, or external drive.
PGA
Pin Grid Array
A CPU package/socket style that uses a grid of pins.
PoE
Power over Ethernet
Technology that carries electrical power along with network data over compatible Ethernet cabling and equipment.
POP3
Post Office Protocol version 3
An email retrieval protocol traditionally associated with downloading messages from a mail server.
Port
Connection point
A physical or logical connection point. Physical examples include USB and Ethernet ports; networking also uses logical port numbers.
POST
Power-On Self-Test
Startup checks performed before the operating system loads.
Proprietary
Manufacturer-specific design
A design controlled by a particular manufacturer that may not follow a common interchangeable standard. Verify compatibility before replacing parts.
PS/2
Personal System/2 connector
A legacy 6-pin mini-DIN connector used for keyboards and mice.
PSU
Power Supply Unit
Converts wall AC into regulated DC power used by a desktop computer.
PWM
Pulse-Width Modulation
Technique that controls average power/signal behavior by changing pulse duty cycle.
PXE
Preboot Execution Environment
A method that allows a computer to boot using resources provided over a network.
RAID
Redundant Array of Independent Disks
A method of combining multiple drives for performance, redundancy, or both, depending on RAID level.
RAID 0
Disk striping
A RAID level that stripes data across drives for performance but provides no redundancy.
RAID 1
Disk mirroring
A RAID level that duplicates data across drives for redundancy.
RAID 10
Mirroring + striping
A RAID level combining mirrored drive pairs with striping; provides redundancy and performance but requires at least four drives.
RAID 5
Striping with distributed parity
A RAID level using block-level striping and distributed parity; requires at least three drives.
RAM
Random Access Memory
Fast volatile working memory used by active programs and data.
RDP
Remote Desktop Protocol
A protocol used for graphical remote access to Windows systems; commonly associated with port 3389.
RFID
Radio-Frequency Identification
Technology that uses radio signals to identify/read tagged objects.
RJ-11
Telephone-style modular connector
A smaller modular connector commonly associated with telephone/DSL connections; not the same as the larger RJ-45-style Ethernet connector.
RJ-45
Registered Jack 45 (common usage)
Term commonly used for the 8P8C modular connector seen on Ethernet cabling.
RPM
Revolutions Per Minute
A rotational-speed measurement commonly used with mechanical hard drives and fans.
RS-232
Legacy serial communication standard
A serial communication standard commonly associated with DB-9 connectors and COM ports on PCs.
RTC
Real-Time Clock
The hardware clock that keeps date and time. A coin-cell battery can help maintain the clock/settings when system power is removed.
SAN
Storage Area Network
A specialized network that provides block-level storage access to servers.
SATA
Serial ATA / Serial Advanced Technology Attachment
Storage interface used by SATA HDDs and SSDs.
SBC
Single-Board Computer
Computer with major components integrated onto one circuit board, such as Raspberry Pi.
SCADA
Supervisory Control and Data Acquisition
Systems used to monitor and control industrial processes and infrastructure.
SDRAM
Synchronous Dynamic Random-Access Memory
DRAM synchronized with the system clock; DDR memory generations are forms of SDRAM.
Serial
Bits sent sequentially
A communication method that sends bits in sequence over a channel. USB and SATA are modern serial technologies; RS-232 is a common legacy serial standard.
Serial Bus
Serial data pathway
A shared communication pathway that transfers data serially. USB and PCIe use serial signaling approaches.
SMB
Server Message Block
A network protocol used for file/printer sharing and related services, especially in Windows environments.
SMTP
Simple Mail Transfer Protocol
A protocol used to send/relay email between systems.
SoC
System on a Chip
Integrated chip combining CPU cores and other system functions/controllers.
SO-DIMM
Small Outline Dual Inline Memory Module
Smaller removable RAM module commonly used in serviceable laptops and compact systems.
Software
Programs and instructions
The non-physical programs, operating systems, apps, utilities, and instructions that tell computer hardware what to do.
SOHO
Small Office/Home Office
A small network environment such as a home office or small business.
SSD
Solid-State Drive
Persistent storage that uses flash memory and has no spinning disk.
SSH
Secure Shell
An encrypted protocol used for secure remote command-line access and related functions such as secure file transfer.
SSID
Service Set Identifier
The network name used to identify a Wi-Fi network.
Standard
Shared technical specification
A defined specification that helps products work together. Examples include USB, PCIe, SATA, Ethernet, and common motherboard form factors.
System Board
Motherboard / main board
Another term for the main circuit board in a computer. The exact term can vary by device and manufacturer.
TCP
Transmission Control Protocol
Connection-oriented transport protocol that provides ordered, reliable delivery.
Thunderbolt
High-speed peripheral interface
A high-speed interface that can carry data and display signals and, depending on version/device, uses Mini DisplayPort or USB-C-style connectors.
TLS
Transport Layer Security
Cryptographic protocol used to protect data in transit, including HTTPS.
TN
Twisted Nematic
LCD panel type commonly associated with fast response and lower cost.
TPM
Trusted Platform Module
Security hardware/firmware technology used for cryptographic functions, key protection, measured boot, and related platform security.
UDP
User Datagram Protocol
Connectionless transport protocol with lower overhead and no built-in delivery guarantee.
UEFI
Unified Extensible Firmware Interface
Modern firmware interface used to initialize hardware and start the boot process.
UPS
Uninterruptible Power Supply
A device that provides temporary battery-backed power and often surge protection when utility power fails.
URL
Uniform Resource Locator
The address used to identify the location of a resource on a network or the web.
USB
Universal Serial Bus
Common interface for peripherals, data transfer, and power.
USB-C
USB Type-C
Reversible connector type that can carry USB data and power; capabilities depend on the device/cable/standard.
Utility
Maintenance/support software
Software designed to configure, diagnose, protect, monitor, or maintain a computer.
V
Volt
Unit of electrical potential difference.
VA
Vertical Alignment
LCD panel type often associated with strong contrast.
VDC
Volts Direct Current
A way to specify direct-current voltage, such as DC voltages supplied to computer components.
VGA
Video Graphics Array
Legacy analog video interface using a 15-pin connector.
VM
Virtual Machine
A software-defined computer environment that runs an operating system and applications using virtualized hardware resources.
VoIP
Voice over Internet Protocol
Technology for carrying voice communications over IP networks.
VPN
Virtual Private Network
Technology that creates a protected logical connection across another network, commonly using encryption.
W
Watt
Unit of power. Power is commonly described by the relationship P = V × I.
WAN
Wide Area Network
A network that connects systems or LANs across larger geographic areas.
Wi-Fi
Wireless networking technology
A family of wireless LAN technologies used to connect devices to local networks. Wi-Fi is not an acronym for “wireless fidelity.”
Windows
Desktop operating system
A widely used PC operating system that manages hardware, applications, files, networking, security, and the user interface. Windows is not an acronym.
WLAN
Wireless Local Area Network
A LAN using wireless networking such as Wi-Fi.
WWAN
Wireless Wide Area Network
A wide-area network connection using wireless technologies such as cellular data.
x86-64
64-bit x86 Architecture
64-bit instruction-set architecture common in Intel/AMD PCs; also called AMD64 in many software downloads.
Important: This is a study quick reference, not an exhaustive replacement for the official CompTIA A+ exam objectives. Keep the current objectives beside your notebook and add unfamiliar acronyms as you encounter them.