| Term | Definition |
| Advanced Graphic Port (AGP) | A video adapter that provides 3-D graphics support and enhanced video processing speed by two means: newer Pentium-based processor chips have circuitry designed to communicate with the AGP adapter and the AGP adapter can communicate directly with the system’s RAM. |
| Air plenum | The open area inside a PC case. The air plenum helps dissipate the heat generated by the processor and other computer components. Air normally flows from the front of the case to the rear of the case where the power supply and cooling fan are located. |
| Alternating Current (AC) | An electrical current that reverses polarity at regular intervals. These intervals are measured in cycles per seconds (CPS) or hertz (Hz). Wall sockets and U.S. households provide 120 volts at 60 Hz. |
| AT Attachment (ATA) disk drive | IDE hard drives are actually ATA disk drives. They are the most popular disk drives because they provide low-cost disk storage. |
| AT Attachment-2 (ATA-2) disk drive | The second-generation enhancement to the original ATA disk standard. |
| Banking | A process developed with the 286 processor that allows a processor to read more than one row of RAM at one time. |
| Beep codes | Error codes that can be generated by the system board when core components of the system are inoperable. The beep codes play through the PC’s internal speaker and provide information about the component that’s failing. |
| Bus | A set of hardware lines or wires that transfer information among the components of a computer system. These lines are specialized for carrying different types of information — data, control signals, or addresses — and are regulated by the microprocessor. |
| Color Graphics Adapter (CGA) | A video adapter that provided support for multicolor data in text or graphics mode. The data provided to the monitor was digital. |
| Direct Current (DC) voltage | An electrical current that travels in one direction and does not reverse polarity. The power supply in a PC converts 120 volts AC into 12 volts DC and 5 volts DC. Batteries are DC. |
| Dual In-Line Memory Module (DIMM) | A RAM package that holds several memory chips on a single circuit board and has a 168-pin single-row edge connector for insertion into the motherboard. |
| Dynamic RAM (DRAM) | RAM chips that must be refreshed constantly. Most RAM in PCs is DRAM. |
| Enhanced Graphics Adapter (EGA) | A video adapter that provided support for multi-color data in text or graphics mode. The data provided to the monitor was digital. |
| Enhanced IDE (EIDE) | An alternate term for the ATA-2 extension of the original ATA (IDE) specification. |
| Enhanced Small Device Interface (ESDI) | An interface created by a consortium of drive manufacturers that provided increased reliability and much higher data throughput. |
| Extended Data Out (EDO) | A new RAM technology that uses a dual-pipeline architecture and lets EDO memory have a timing overlap between successive accesses, which provides an overall increase in memory efficiency of about 20 percent. |
| Extended Industry Standard Architecture (EISA) bus | A bus architecture that provides a 32-bit extension to the ISA bus standard. This bus is able to operate at 12 MHz. |
| Floating Point Unit (FPU) | A floating-point processor that speeds up floating-point and transcendental math operations 10 to 50 times (also called a co-processor). The co-processor portion of the 386DX, 486, and Pentium is built into the main processor chip and lets the processor multiply quickly. |
| Footprint | The surface area occupied by a personal computer or peripheral. |
| Industry Standard Architecture (ISA) bus | An industry standard bus architecture that provides an 8-bit and 16-bit standard interface for expansion cards. The ISA bus operates at 8 MHz. |
| Integrated Drive Electronics (IDE) | A general term for drives that have built-in disk controllers. Also, the popular term used for AT Attachment (ATA) disk drives. |
| Interface card | A card that lets you install capabilities in a PC that are not provided by the core components. |
| Modified Frequency Modulation (MFM) encoding | An encoding scheme that reduces the number of flux reversals used to store data on a hard disk. MFM replaced the FM encoding scheme and is currently used on today’s floppy disk drives. |
| Monochrome Display Adapter (MDA) | The original video adapter used in PCs that provided one-color, text-based digital data to a monochrome monitor. |
| Non-volatile memory | Permanent memory, in which all data remains intact when power is removed from the system. The hard disk is a form of non-volatile memory. |
| Odd parity | A parity checking scheme in which the other bits are totaled, and if the total is an odd number, a parity bit is added. If the total is even, the parity bit is set to zero. This correction technique or memory errors can detect single-bit memory failures only. |
| Parity | A procedure that determines errors in transmitted data by checking to be sure that the number of 1s in a set of data is always the same (either an even number or an odd number). |
| PC Card (PCMCIA) | A card that provides expandability for notebook computers and comes in three thicknesses: Type I, Type II, and Type III. |
| Peripheral Component Interconnect (PCI) bus | The most widely used and accepted expansion bus. PCI is a mezzanine bus that operates between the expansion bus and the system bus. |
| Pipeline | A portion of memory that one process uses to pass information to another process. Pipelining increases processes execution speed by ensuring that the microprocessor doesn’t have to wait for instructions — when the microprocessor executes one instruction, another is waiting. |
| Plug and Play (PNP) | An I/O card technology that lets the system BIOS or operating system configure any new cards added to a PC expansion slot. |
| Random Access Memory (RAM) | The chip that temporarily stores data for the processor. The operating system, applications, and data all pass through RAM. |
| Read-Only Memory (ROM) | A semiconductor-based memory that permanently stores data. The BIOS chip on a PC’s motherboard is a ROM chip. |
| Run Length Limited (RLL) Encoding | An encoding scheme that can store 50 percent more data on a disk than MFM encoding. The RLL encoding method is still used in many of today’s disk drives. |
| Single Edge Contact (SEC) connector | A specially designed socket that houses the Pentium II processor on IBM-compatible motherboards. |
| Single In-Line Memory Module (SIMM) | A RAM package that holds several memory chips on a single circuit board and has a 30-pin or 72-pin single row edge connector for insertion into a motherboard socket. |
| Single In-Line Pinned Package (SIPP) | A RAM package that holds several memory chips on a single circuit board and has a single row of 30 pins for insertion into a motherboard socket. |
| Small Computer System Interface (SCSI) | A system-level interface that supports up to eight devices, with one of the devices being the host adapter (controller). |
| Static RAM (SRAM) | RAM chips that do not have to be refreshed by a refresh cycle — the refresh circuitry is built into the RAM chip. L-2 cache is a form of static memory. |
| Super VGA (SVGA) | An enhanced version of the VGA standard that provides greater than 1280 x 1024 resolution with 16 million colors. |
| Synchronous Dynamic RAM (SDRAM) | A new RAM technology that ties RAM access to the system clock and accepts pipeline instructions, which lets SDRAM perform four to six times more efficiently than DRAM. |
| Synchronous Graphics RAM (SGRAM) | A kind of RAM that works in the same manner as SDRAM but is specially designed for video cards only. |
| VESA Local (VL) bus | A bus architecture that provides fast video communications. The VL bus can operate at 33 MHz. |
| Video Graphics Array (VGA) | A video adapter that provides analog data to a monitor. The resolution is 640 x 480 pixels and 16 colors. |
| Video RAM (VRAM) | A specially designed video memory that provides dual-ported access, which lets the video board receive data from the system while writing data to the video output port. |
| Volatile memory | Temporary memory, in which all data is erased when power is removed from the system. RAM is an example of volatile memory. |
| Windows RAM (WRAM) | A video RAM that works much like VRAM but is slightly more efficient. |
| Zero Insertion Force (ZIF) socket | A specially designed socket that makes it safer and easier to insert a chip. Modern PC motherboards use the Socket 3 and the Socket 7 ZIF socket to house the 486 and Pentium chips. |
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