Compendium of ComputerTerms and Acronyms


ASCII (American Standard Code for Information Interchange) Pronounced "asskee." A standard developed by the American National Standards Institute (ANSI) describing how characters can be represented on a computer. The ASCII character set consists of 128 characters numbered from 0 to 127 and includes numerals, punctuation symbols, letters, and special control codes such as end-of-line characters. The letter A, for example, is represented by the number 65. With Windows NT being a notable exception, most personal computers use some form of the ASCII character set. (Windows NT uses the newer and more expansive Unicode character set.)

ASIC (Application-Specific Integrated Circuit) An integrated-circuit chip designed for a particular use rather than general use. Many video boards and modems use ASICs.

ATA (AT Attachment) The specification that defines the IDE drive interface. AT refers to the IBM PC/AT personal computer and its bus architecture. IDE drives are sometimes referred to as ATA drives. The newer ATA-2 specification defines the EIDE interface, that improves upon the IDE standard. See also IDE and EIDE.

BBS (Bulletin Board System) A term for a dial-up on-line system that users can use to download software, leave messages for other users, and exchange information. MPM's BBS is used exclusively for software downloading.

BIOS (Basic Input / Output System) Pronounced "bi-ohs" The set of low-level routines in a computer's ROM that application programs (and operating systems) can use to read characters from the keyboard, output characters to printers, and interact with the hardware in other ways. Many plug-in adapters include their own BIOS modules that work in conjunction with the BIOS on the system board.

bit The smallest fragment of computer information. Usually represented by a logical 1 (one) or 0 (zero).

byte Usually a contiguous group of bits, usually 8, that represent a complete piece of usable computer information. Typically, an individual character, such as the letter 'A', can be represented in a single byte.

CPU (Central Processing Unit) In the PC industry, CPU refers to the microprocessor chip that powers a personal computer. The Intel Pentium chip is one example of a CPU. The term sometimes also loosely refers to the case that houses this chip. See also FPU.

CRC (Cyclical Redundancy Check) A mathematical method that permits errors in long runs of data to be detected with a very high degree of accuracy. CRC error checking is often used by hard disk mechanisms.

DIMM (Dual In-line Memory Module) Pronounced "dimm." A memory device that consists of a PCB board with a row of contact points on both sides of the PCB and several memory chips, usually DRAM, attached to the PCB. The PCB board provides the connection between the multiple memory chips and the computer system in a single component versus the numerous components required when using individual chips. The term generally refers to the 168-pin DIMM module based on a JEDEC specification. See also SIMM and SO DIMM.

DRAM (Dynamic Random Access Memory) Pronounced "dee-ram." The volatile memory used to temporarily store data in personal computers. DRAM stores each bit of information in a "cell" composed of a capacitor and a transistor. Since the capacitor in a DRAM cell can hold a charge for only a few milliseconds, DRAM must be continually refreshed, or recharged, to retain its data. Static RAM, or SRAM, requires no refresh and delivers better performance, but it is more expensive to manufacture. See also EDO RAM and SRAM.

ECC (Error Correcting Code) Parity checking provides single-bit error detection for the system memory, but does not handle multi-bit errors, and provides no way to correct memory errors. An advanced error detection and correction protocol was invented to go a step beyond simple parity checking. Called ECC, which stands for error correcting circuits, error correcting code, or error correction code, this protocol not only detects both single-bit and multi-bit errors, it will actually correct single-bit errors on the fly, transparently.

EDO RAM (Extended Data-Out Random Access Memory) A form of DRAM that speeds accesses to consecutive locations in memory by assuming that the next memory access will target an address in the same transistor row as the previous one and latching data at the output of the chip so it can be read even as the inputs are being changed for the next memory location. EDO RAM can reduce memory access times compared with standard DRAM chips of the same speed and costs only a little more to manufacture.

EDRAM (Enhanced Dynamic Random Access Memory) A form of DRAM that boosts performance by using a comparatively small amount of static RAM (SRAM) in each DRAM chip as a cache. Also known as cached DRAM, or CDRAM.

EEPROM (Electrically Erasable Programmable Read-Only Memory) Pronounced "ee-ee-prom." Read-Only Memory (ROM) that can be erased and rewritten electrically. EEPROM is frequently used for system-board BIOSes to permit a computer's BIOS to be updated without replacing the chips. See also ROM and BIOS.

EIDE (Enhanced Integrated Device Electronics or Enhanced Intelligent Drive Electronics) An enhanced version of the IDE drive interface that expands the maximum disk size, increases the maximum data transfer rate, and supports up to four drives per PC (as opposed to two in IDE systems). See also IDE and SCSI.

EISA (Extended Industry Standard Architecture) Pronounced "ee-suh." A 32-bit bus architecture developed by a consortium of computer vendors, including Compaq, to counter IBM's proprietary Micro Channel (MCA) architecture. Unlike Micro Channel, EISA is backward-compatible with cards designed for the ISA bus. Like MCA, EISA never gained wide market acceptance.

EMS (Expanded Memory Specification) A bank-switched memory management scheme developed by Intel, Lotus, and Microsoft that allows MS-DOS applications (normally limited to 640K of memory) to access vast quantities of memory. Memory that conforms to this standard is often referred to as expanded memory. EMS memory is rarely used today, as protected-mode operating systems such as Windows, makes it obsolete.

EPROM (Erasable Programmable Read-Only Memory) Pronounced "ee-prom." Read-Only Memory (ROM) that can be erased by high-intensity ultraviolet (UV) light and then rewritten, or "reprogrammed." EPROM chips normally contain UV-permeable quartz windows to permit exposure for erasing the program that also exposes the chips' internals. This window is usually covered. See also ROM and EEPROM.

FAT (File Allocation Table) Pronounced "fat." The file system used by DOS to manage files stored on hard disks, floppy disks, and other disk media. The name is taken from the on-disk data table known as the file allocation table that records where individual portions of each file are located on the disk. See also VFAT.

FPU (Floating-Point Unit) Refers to a math coprocessors found in many personal computers. The Intel 80387 is one example of an FPU. FPUs perform certain calculations faster than CPUs because they specialize in floating-point math, whereas CPUs are geared for integer math. Many CPU's have the FPU integrated rather than packaged and sold separately. See also CPU.

FTP (File Transfer Protocol) A set of rules that allows two computers to talk to each other as a file transfer is carried out. This is the protocol used when you download a file to your computer from another computer on the Internet.

HPFS (High Performance File System) OS/2's native file system. HPFS offers superior performance compared to the FAT file system, support for long filenames, and can handle hard disks of virtually any size with significantly less waste caused by the large cluster sizes of FAT. See also FAT, NTFS.

IDE (Integrated Device Electronics or Intelligent Drive Electronics) A hard drive-interface specification that integrates all the drive control electronics on the drive itself, rather than on the adapter connecting the drive to the expansion bus. This integration shortens the signal paths between drive heads and controller, permitting higher data transfer rates and simplifying adapter cards. The IDE specification has replaced the Enhanced Small Device Interface (ESDI) specification that has mose of the drive electronics on the controller card. See also EIDE and SCSI.

I/O (input/output) A general term that describes any action that sends and receives data on a computer. The term "file I/O," for example, refers to the act of reading or writing information in a disk file.

IRQ (Interrupt ReQuest) A signal from a hardware device such as a keyboard or a drive controller indicating that it needs the CPU's attention. IRQ signals are transmitted along IRQ lines, which connect peripheral devices to an interrupt controller. The interrupt controller prioritizes the incoming interrupt requests from the different devices and delivers them to the CPU.

ISA (Industry Standard Architecture) Pronounced "eye-suh or simply eye-ess-ay" The bus design of the IBM PC/AT and all the PC compatible computer systems used today. See also EISA and MCA.

JEDEC (Joint Electron Device Engineering Council) The consortium of manufacturers that devises standards most notably for computer memory modules. Industry Standard memory usually implies compliance with a particular group of JEDEC standards.

NTFS (NT File System) The native file system of Microsoft Windows NT. NTFS offers superior performance compared to the FAT file system, excellent security, and can handle hard disks of virtually any size with significantly less waste caused by the large cluster sizes of FAT. See also FAT and HPFS.

PARITY Parity checking is a rudimentary method of detecting simple, single-bit errors in a memory system. It in fact has been present in PCs since the original IBM PC in 1981, and until the early 1990s was used in every PC sold on the market. It requires the use of parity memory, which provides an extra bit for every byte stored. This extra bit is used to store information to allow error detection.

PCI (Peripheral Component Interface) A local bus architecture that is widely used in Pentium-based PCs that provides a high-bandwidth data channel between system-board components such as the CPU and devices such as hard disks and video adapters. PCI is one of two widely adopted local-bus standards. The other, the VL-Bus, is primarily used in 486 PCs. See also VLB.

PCL (Printer Control Language) PCL defines a standard set of commands for communicating with HP or HP-compatible printers. PCL has become a de facto standard for laser and ink jet printers and is supported by virtually all printer manufacturers. HP compatible or LaserJet compatible means that a printer supports the most common PCL commands.

PCMCIA (Personal Computer Memory Card International Association) The consortium of computer manufacturers that devised the standard for the credit-card style adapter cards used in many notebook computers. PCMCIA defines three card types: Type I cards that can be up to 3.3 mm thick and are generally used for RAM and ROM expansion cards; Type II cards that can be as thick as 5.5 mm and typically house modems and fax modems; Type III cards that can be as thick as 10.5 mm and are mostly used for hard disks. PCMCIA support is a major component of Windows 95's Plug and Play architecture, which automatically recognizes when PCMCIA devices are added and removed. (The term PC Card has replaced PCMCIA acronym when referring to the cards themselves.)

PIF (Program Information File) Pronounced "piff." A file used by Microsoft Windows 3.x to store configuration information about a DOS program.

PnP (Plug and Play) The technology that lets Windows 95 automatically detect and configure most of the adapters and peripherals connected to a PC. A fully Plug and Play-enabled PC requires three PnP components: a PnP BIOS, PnP adapters and peripherals, and a PnP operating system. In theory, adding a PnP-compliant device to a PnP PC requires little more than making the physical connection. The operating system, in conjunction with PnP logic present in the BIOS and in the device itself, handles the IRQ settings, I/O addresses, and other technical aspects of the installation to ensure that the device doesn't conflict with other installed devices.

PPP (Point-to-Point Protocol) A protocol used to connect a personal computer to the Internet through a dial-in connection. PPP is generally considered to be superior to SLIP, because it features error detection, data compression, and other elements of modern communications protocols that SLIP lacks. See also SLIP.

RAM (Random Access Memory) Pronounced "ram." The generic term for memory used in modern computers that can be read from and written to in a direct, or random, method. RAM comes in many forms, and manufacturers are continually coming up with new designs to provide the fastest possible access times at the lowest possible cost. See also DRAM, EDO RAM, SRAM, and VRAM.

ROM (Read-Only Memory) Pronounced "romm." The generic term for the non-volatile memory that can be read from but not written to. A computer's BIOS is typically contained in ROM. By using ROM, the code and data in the ROM BIOS need not be reloaded each time the computer is started, and they're protected from corruption caused by malfunctioning applications that attempt to write into the wrong part of memory. Some forms of ROM can be rewritten by applying higher-than-normal voltages to the inputs and holding the voltages for several milliseconds. See also BIOS, EPROM, and EEPROM.

SCSI (Small Computer System Interface) Pronounced "scuzzy." A bus interface used for peripheral connection popularized on the Apple Macintosh and used primarily to connect hard disks, CD-ROM drives, tape drives, and other mass-storage devices to PCs of all types. The SCSI interface excels at handling large hard disks and permits up to seven devices to be connected along a single bus provided by a SCSI connection. See also IDE.

SIMM (Single In-line Memory Module) Pronounced "simm." A memory device that consists of a PCB board with a single row of contact points and several memory chips, usually DRAM, attached to the PCB. The PCB board provides the connection between the multiple memory chips and the computer system in a single component versus the numerous components required when using individual chips. See also DIMM and SO DIMM

SLIP (Serial Line Internet Protocol) Pronounced "slip." A protocol used to connect a personal computer to the Internet through a dial-in connection. SLIP is also used to run TCP/IP over phone lines. See also PPP and TCP/IP.

SO DIMM (Small Outline Dual In-line Memory Module) Pronounced "es-oh dimm." A memory device that consists of a PCB board with a row of contact points on both sides of the PCB and several memory chips, usually DRAM, attached to the PCB. The PCB board provides the connection between the multiple memory chips and the computer system in a single component versus the numerous components required when using individual chips. The term generally refers to the 72-pin SO DIMM module based on a JEDEC specification. See also SIMM and DIMM.

SRAM (Static Random Access Memory) Pronounced "es-ram." A form of RAM that retains its data without the constant refreshing, or recharging, that DRAM requires. SRAM is generally preferable to DRAM because it offers faster memory access times (a critical element in a PC's performance), but it is also more expensive to manufacture because it contains more electrical components. The most common use for SRAM is to cache data traveling between the CPU and a RAM subsystem populated with DRAM to boost performance by reducing the number of DRAM accesses required. See also DRAM.

TCP/IP (Transmission Control Protocol/Internet Protocol) A set of communication protocols developed by the U.S. Department of Defense that allows dissimilar computers to share information over a network. See also PPP and SLIP.

TSR (Terminate, Stay-Resident) The common name for a DOS program that terminates and remains resident in memory so they can operate in the background while other programs execute in the foreground.

UMB (Upper Memory Block) A block of memory (between 640K and 1MB) created in upper memory by a 386 memory manager. This is useful for loading TSRs and device drivers so they don't occupy the limited memory below 640K. See also TSR.

URL (Uniform Resource Locator) A logical address that identifies a resource on the Internet. For example, the URL

http://www.goldenram.com/

is the Internet address of a Web page that gives you access to the MPM GoldenRAM Home Page. In this example, http names the protocol (HyperText Transfer Protocol) used to access the page; www stands for World-Wide Web; goldenram is the institution that operates the server computer, in this case MPM GoldenRAM; and .com signifies company (as opposed to .gov for government, .org for nonprofit organization, or .edu for educational institution).

VESA (Video Electronics Standards Association) Pronounced "vee-suh." The consortium of computer manufacturers responsible for the SVGA video standard and the VL-Bus, a local-bus architecture. See also SVGA and VLB.

VFAT (Virtual File Allocation Table) Pronounced "vee-fat.". An extension of the FAT file system, VFAT is the 32-bit file system that Windows 95 uses to manage information stored on disks. VFAT supports long filenames while retaining compatibility with (and many of the limitations of) FAT volumes. See also FAT.

VLB (VESA Local Bus or VL-Bus) The local-bus standard created by the Video Electronics Standards Association (VESA) to provide a fast data connection between CPUs and local-bus devices. The VL-Bus was widely used in 486 PCs, but most Pentium PCs use PCI local buses instead. See also PCI.

VRAM (Video Random Access Memory) Pronounced "vee-ram." A form of DRAM specially suited for video adapters. VRAM differs from common DRAM in that it features a "dual-ported" design allowing two devices to access it at once. Thus the CRT controller (which converts bits and bytes in video memory to pixels on the screen) and the CPU (which manipulates the contents of video memory) can access VRAM simultaneously. Video boards using VRAM tend to perform better than those using less expensive DRAM. See also DRAM and WRAM.

WRAM (Windows Random Access Memory) Pronounced "double-you-ram." Similar to VRAM, but with added logic designed to accelerate common video functions such as bit-block transfers and pattern fills. WRAM is priced competitively with VRAM and can substantially speed up certain graphical operations such as video playback and screen animation. See also VRAM.

WWW (World-Wide Web) A collection of richly formatted hypertext "pages" located on computers around the world and logically linked together by the Internet. Users can access different Web pages by clicking highlighted words on their screen. Each click activates a hypertext link, connecting the user to another Web location identified by a URL. See also HTML and URL.

XMS (Extended Memory Specification) A memory allocation scheme that allows programs to use extended memory (memory above 1MB) without interfering with each other. Access to XMS memory is facilitated by an XMS driver such as Microsoft's HIMEM.SYS, which is supplied with Windows.