AC
Alternating Current
Electrical power that periodically reverses direction; wall power is AC.
A+ quick reference
Decode the acronyms before they slow you down.
Search the abbreviations used across the missions. When an acronym appears in your notebook, write both the full name and what it actually does.
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Notebook rule: Do not write only “DIMM = Dual Inline Memory Module.” Add the useful clue: “full-size removable desktop RAM module.” That is the information that helps on a scenario question.
DC
Direct Current
Electrical current that flows in one direction. Computer components operate on regulated DC power.
A
Ampere / Amp
Unit of electrical current. Context matters: the letter A can also simply be an answer label.
V
Volt
Unit of electrical potential difference.
W
Watt
Unit of power. Power is commonly described by the relationship P = V × I.
ESD
Electrostatic Discharge
A sudden transfer of static electricity that can damage electronic components.
PSU
Power Supply Unit
Converts wall AC into regulated DC power used by a desktop computer.
CPU
Central Processing Unit
Executes program instructions and performs calculations.
GPU
Graphics Processing Unit
Processes graphics and highly parallel workloads.
RAM
Random Access Memory
Fast volatile working memory used by active programs and data.
DIMM
Dual Inline Memory Module
Full-size removable RAM module common in desktop computers.
SO-DIMM
Small Outline Dual Inline Memory Module
Smaller removable RAM module commonly used in serviceable laptops and compact systems.
DDR
Double Data Rate
Family of synchronous DRAM technologies; generations include DDR3, DDR4, and DDR5.
LPDDR
Low-Power Double Data Rate
Low-power memory commonly used in mobile and integrated devices; Pi 5 uses LPDDR4X.
HDD
Hard Disk Drive
Magnetic persistent storage with moving mechanical parts.
SSD
Solid-State Drive
Persistent storage that uses flash memory and has no spinning disk.
SATA
Serial ATA / Serial Advanced Technology Attachment
Storage interface used by SATA HDDs and SSDs.
eSATA
External SATA
External version of SATA; legacy compared with modern USB/Thunderbolt storage connections.
NVMe
Non-Volatile Memory Express
Protocol designed for high-speed solid-state storage over PCIe.
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.
PCIe
Peripheral Component Interconnect Express
High-speed expansion interface used for GPUs, NICs, NVMe storage, and other devices.
PCI
Peripheral Component Interconnect
Older/legacy expansion-bus standard that is physically different from PCIe.
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.
HDMI
High-Definition Multimedia Interface
Digital audio/video interface used with displays.
DP
DisplayPort
Digital display interface supporting audio/video and high resolutions/refresh rates.
DVI
Digital Visual Interface
Older display interface that can carry digital video; some variants support analog.
VGA
Video Graphics Array
Legacy analog video interface using a 15-pin connector.
LCD
Liquid Crystal Display
Flat-panel display technology that uses liquid crystals and a backlight.
OLED
Organic Light-Emitting Diode
Display technology where pixels emit their own light.
IPS
In-Plane Switching
LCD panel type known for viewing angles and color reproduction.
TN
Twisted Nematic
LCD panel type commonly associated with fast response and lower cost.
VA
Vertical Alignment
LCD panel type often associated with strong contrast.
NIC
Network Interface Card / Controller
Hardware interface that connects a device to a network.
RJ-45
Registered Jack 45 (common usage)
Term commonly used for the 8P8C modular connector seen on Ethernet cabling.
LAN
Local Area Network
Network covering a limited local area such as a home, school, or office.
WLAN
Wireless Local Area Network
A LAN using wireless networking such as Wi-Fi.
IP
Internet Protocol
Provides logical addressing and routing between networks.
MAC
Media Access Control
Link-layer addressing associated with network interfaces.
DNS
Domain Name System
Translates names such as websites into IP addresses.
DHCP
Dynamic Host Configuration Protocol
Automatically provides clients with IP configuration information.
TCP
Transmission Control Protocol
Connection-oriented transport protocol that provides ordered, reliable delivery.
UDP
User Datagram Protocol
Connectionless transport protocol with lower overhead and no built-in delivery guarantee.
HTTP
Hypertext Transfer Protocol
Web application protocol; unencrypted HTTP does not provide TLS protection.
HTTPS
Hypertext Transfer Protocol Secure
HTTP protected by TLS.
TLS
Transport Layer Security
Cryptographic protocol used to protect data in transit, including HTTPS.
OS
Operating System
Software layer that manages hardware and provides services for applications.
UEFI
Unified Extensible Firmware Interface
Modern firmware interface used to initialize hardware and start the boot process.
BIOS
Basic Input/Output System
Legacy firmware term; often used generically, but modern PCs commonly use UEFI.
POST
Power-On Self-Test
Startup checks performed before the operating system loads.
SBC
Single-Board Computer
Computer with major components integrated onto one circuit board, such as Raspberry Pi.
SoC
System on a Chip
Integrated chip combining CPU cores and other system functions/controllers.
ARM64
64-bit Arm Architecture
64-bit software/processor architecture label used by many Arm-based systems.
x86-64
64-bit x86 Architecture
64-bit instruction-set architecture common in Intel/AMD PCs; also called AMD64 in many software downloads.
GPIO
General-Purpose Input/Output
Programmable pins on boards such as Raspberry Pi used to interface with electronics.
FFC
Flat Flexible Cable
Thin flexible cable used for compact internal connections; Pi 5 exposes PCIe through an FFC connector.
PWM
Pulse-Width Modulation
Technique that controls average power/signal behavior by changing pulse duty cycle.
CLI
Command-Line Interface
Text-based interface where users enter commands.
GUI
Graphical User Interface
Visual interface using windows, icons, menus, and pointers/touch.
COM
Communications Port
Windows name for serial communication ports, historically associated with RS-232.
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.