Glossary of terms





ALU   ALU (Arithmetic Logic Unit) is the part of the CPU where the arithmetic and logic operations are performed.
ASCII   ASCII (American Standard Code for Information Interchange) is a binary data code used in all personal computers and commmunication services.
Asynchronous transmission   Serial data transmission where the receiving system is not synchronized with the transmitting system.
ATAPI   ATAPI (AT Attachment Packet Interface) is an extension to EIDE (also called ATA-2) that enables the interface to support CD-ROM players and tape drives.
AT   The form factor used by most PC motherboards prior to 1998. The original motherboard for the PC-AT measured 12"x13". Baby AT motherboards are a little smaller, usually 8.5"x13"
AT bus   Also known as ISA bus. It is the 16-bit data bus of the AT class PCs.
ATX   The modern-day shape and layout of PC motherboards. Supports a soft power switch. It improves on the previous standard, the Baby AT, by rotating the orientation of the board 90 degrees. The CPU is closer to the power supply and cooling fan. The disk drive cable connectors are nearer to the drive bays


BAT file   File extension used to identify a batch file (a list of DOS commands) in DOS.
Baud rate   Number of electrical state changes per second on a data communication line. For lower speeds it can be the same as the bits-per-second rate, but at higher speeds it usually is less than the bits-per-second rate.
BIOS   Stored in the CMOS, the Basic Input/Output System (BIOS) is the software for communications between the PC and its peripherals.
Bit   One digit of a binary number (0 or 1)
Bitmap   Memory area containing a video image. One bit represents one pixel (monochrome) or several bits represent one pixel (grayscale or color).
BNC   A coaxial network cable connector.
Bps   (bits-per-second) measures the speed of data transferred
Buffer   Memory register used to match data transfer speeds between the computer and a peripheral.
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Cache   Cache is a high-speed type of RAM used to store information frequently used by the processor. L1 is built into the processor, and L2 is outside the processor.
Centronics   36-pin standard for interfacing parallel printers and other devices.
CGA   CGA (Color Graphics Adapter) low-resolution stadard for text and graphics.
Checksum   Numeric value assigned to a block of data used to detect memory errors.
Coaxial   10Base5 network cable with 10Mbps transfer rate. Coaxial cables use BNC connectors.
Control Panel   The tool in Windows which allows the user to adjust system settings.
CMOS   The CMOS (Complementary Metal Oxide Semiconductor) chip contains the system BIOS, setup configuration information, and the date/time. The information is retained after the power is turned off by using a small battery
Computer word   Data format inside the computer. There are three types of computer words: numeric words, alphanumeric words, instruction words.
CPU   The CPU (Central Processing Unit) is the "brain" of the computer. Consists of the control unit and the ALU. Performs all math and control functions in the PC.
CRT   A CRT (Cathode Ray Tube) is the vacuum display tube in a PC monitor.




DAC   (Digital to Analog Converter) - converts a binary coded signal (digital) into a continuously variable signal (analog).
Data bus   A bidirectional path between the CPU and memory and I/O devices.
DIMM   A DIMM (Dual Inline Memory Module) is a 168-pin RAM module with a 64-bit bus to the individual chips, to allow chips to be added one at a time.
DMA   A DMA (Direct Memory Access) is a channel for transferring from a I/O device without involving the CPU. AT PCs have 8 DMA channels while XT PCs have 4 DMA channels.
Dot pitch   Measures the resolution of a dot matrix


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Earth ground   Electrical reference point of absolute zero.
EEPROM   EEPROM (Electronically Erasable Programmable Read Only Memory) - non-volatile memory device which can be erased and reprogrammed using special circuitry
EIDE   EIDE (Enhanced IDE) is a newer version of the IDE mass storage device interface standard. It supports data rates of between 4 and 16.6 MBps. It can also support mass storage devices of up to 8.4 gigabytes.
EISA   EISA (Extended Industry Standard Architecture) is a bus architecture designed for PCs using an Intel 80386, 80486, or Pentium microprocessor. EISA buses are 32 bits wide and support multiprocessing.
EMS   EMS (Expanded Memory) is converted from extended memory as needed by the DOS EMM386 memory manager. Expanded memory allows faster access.
EMI   Electronic radiation disrupting the normal functions of a computer system. It is not permanent and is recoverable.
EPROM   EEPROM (Erasable Programmable Read Only Memory) - non-volatile memory device which can be programmed more than once.
ESD   ESD (Electro-static Discharge) is a static shock and it can destroy IC chips. More often encountered in cold and humid conditions.
ESDI   (Enhanced Small Device Interface) - older interface standard for connecting disk and tape units to computers. Up to 1 GB of data and 1-3 MB/sec transfer rate.




FAT   A FAT (File Allocation Table) is a table that the operating system uses to keep track of where specific data is stored on disk. DOS, Windows 3.x and Windows 95 use FAT16, a 16-bit FAT table, and WIndows 95 OSR2.1 and Windows 98 use FAT32. The advantage of FAT32 is the ability to have larger partitions and smaller clusters, which wastes less space on a disk.
Firmware   Software which is permanently stored on an IC chip.
Form Factor   The size, shape, an dimensions of a motherboard. Common form factors are AT, Baby AT, and ATX.
FRU   A FRU (Field Replaceable Unit) is a component of a PC which can be replaced in the field, which takes no special devices (such as a soldering iron) to install.
Full-duplex   A full-duplex device can send and receive data simultaneously.
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GUI   A GUI (Graphical User Interface) is a way to interact with a PC using images instead of text, such as used in Windows 95.
Ground   Any point from which electrical measurements are referenced.




Handshaking   Signal exchange between thePC and a peripheral device during data transfer.
HGC   HGC (Hercules Graphic Card) - monochrome graphics standard used in early PCs. 720x348 pixels resolution
HMA   The HMA (High Memory Area) is the memory range between 1024k-1088k, and is reserved memory used by one application or utility.




IC   An IC (Integrated Circuit) is a microchip. An IC is sensitive to Electro-static Discharge (ESD).
IDE   IDE (either Intelligent Drive Electronics or Integrated Drive Electronics) is an interface for mass storage devices, in which the controller is integrated into the disk or CD-ROM drive. IDE has been replaced with the newer EIDE standard.
I/O   Data transfer between the CPU and a peripheral device.
I/O Controller   A card in a PC which controls hard disks and floppy drives and usually includes serial and parallel ports. This is integrated into the motherboard on newer PCs.
IRQ   An IRQ (Interrupt Request) signal sent to the CPU by a I/O device during program execution in order to get the attention of the CPU
ISA   ISA (Industry Standard Architechture) is the 16-bit bus architecture used in the older IBM PC/XT and PC/AT PCs, and the AT version of this bus became the industry standard. Starting in the early 90s, ISA began to be replaced by the PCI local bus architecture.
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LAN   A Local Area Network, such a network in a single building or campus.
LCD   An LCD (Liquid Crystal Display) is the flat-screen, fixed-pixel type of display used in laptops.
LSI   (Large Scale Integration) - IC devices containing 3,000 - 100,000 electronic components




MAN   A Metropolitan Area Network
MCA   An MCA (Micro Channel Architecture) bus slot is a 32-bit expansion slot which was developed by IBM, totally incompatible with the PC bus.
Memory   Temporary, fast access data storage usually in the form RAM or ROM.
Modem   ( Modulator-Demodulator) - device which communicates with other modems via a telephone line.
MOS   (Metal Oxide Semiconductor) - memory chip which does not require a highly regulated +5 V DC power supply
Motherboard   The motherboard is the large primary board in the PC to which all other devices directly or indirectly connect. The motherboards is also known as the System board, main logic board, planar board, or mainboard.
Multitasking   The ability of a computer to run several programs at the same time.




NIC   A Network Interface Card, used to connect a PC to a network.
NTSC   (National Television Standards Committee) - US television standard
Null modem cable   A RS-232 cable used to connect two computers physically close to one other, using their serial ports.
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Odd parity   Parity checking where the parity bit is used to make the total numbers of 1s contained in the character an odd number.
Output device   Any peripheral device that accepts computer output. E.g. monitor, modem, printer.




Parity   Parity is an error-checking system where 1 bit is added to every 8 which move in and out of system memory. This bit is called the parity bit, and will change to be a 1 or 0 depending on the number of 1 or zeroes in the 8 bits it accompanies. The system compares this bit to what it expects, and any inconsistencies generate a parity error. Not all memory uses parity.
Partition   An isolated section of a hard drive which is assigned its own drive letter.
PC bus   8-bit bus architecture used in the original IBM PC
PCI   A PCI (Peripheral Component Interconnect) bus slot is a 32 and 64-bit modern expansion slot in a PC. PCI replaces ISA and EISA.
PCMCIA   PCMCIA (Personal Computer Memory Card International Association) slots are 16-bit expansion slots for portable PCs, using credit-card sized cards, called PC Cards. The slots support hot-swapping.
PIF   A PIF (Program Information file) file is a type of file in Windows that holds information about how Windows should run a non-Windows application, such as a DOS application. In Windows 95, PIF files appear as shortcus.
Pitch   Numbers of characters per inch
Pixel   Smallest unit of a display image
PnP   PnP (Plug and Play) is the ability of a computer system to automatically detect and configure expansion boards and other devices. PnP was first introduced to PCs with Windows 95.
Processor   See CPU
Program Manager   The primary user interface in Windows 3.x.




RAM   RAM (Random Access Memory) is temporary, fast access data storage. See Domain 4 of the 220-101 Study Guide for information on specific RAM types.
Real-time clock   See RTC
Registry   The Registry is a database of settings for Windows, Windows applications, users, and installed hardware.
Resolution   Monitor - number of dots per scan line x number of scans per picture

Printer - number of dots per linear inch of print space.

ROM   ROM (Read-Only Memory) is a pre-programmed chip containing firmware. There are several different types of ROM chips, including PROM, EPROM, EEPROM.
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SCSI   SCSI (Small Computer System Interface) is a parallel interface used to connect peripherals. Devices are connected in a daisy chain, meaning each device is connected to the next in a chain. Each SCSI device must have a unique SCSI ID number, with 8 IDs available (0-7), ID 7 in use by the SCSI adapter itself. Each end of a daisy chain must have a terminator. A SCSI bus allows faster data access and uses only 1 IRQ per adapter.
SIMM   A SIMM (Single Inline Memory Module) is a 32-pin or 70-pin RAM module with a 32-bit bus to the individual chips.
SRAM   A SRAM (Static Random Access Memory) is a type of RAM which can store data indefinitely as long as power is applied to it.
SVGA   SVGA (Super VGA) is the modern standard for display adapters, and allows up to 1600x1200 resolution, with up to 16 million colors.
Swap file   See Virtual memory




Task switching   Changing of one program to another under the control of a multitaking operating system environment.
Terminator   A resistor which must be at both ends of a SCSI chain to prevent signals from reflecting back down the bus.
Toner   A very fine powder bonded to iron particles used to generate images in laser printers. Comprised primarily of iron oxide and plastic resin.
Twisted pair   10BaseT or 100BaseT network cabling which uses RJ45 end connectors.




UART   UART (Universal Asynchronous Receiver Transmitter) - a serial interface IC used for conversions required for asynchronous data transmission.
UMB   The UMB (Upper Memory Band) is the memory range from 640k-1024k, and is used for DOS device drivers, to free up conventional memory.
UNC   Windows 95 Universal Naming Convention (UNC) for networks follows the format \\COMPUTERNAME\SHARENAME.
UPS   A UPS (Uninterruptible Power Supply) is a device which protects against power sags and loss by providing battery backup power.
URL   An URL (Universal Resource Locator) is a unique address on the World Wide Web used to access a website.
USB   USB (Universal Serial Bus) is a new external bus standard that supports data transfer rates of 12 Mbps, in 8, 16, 32, or 64 byte packets. A single USB port can be used to connect up to 127 peripheral devices. USB also supports hot-swapping.
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VGA   VGA (Video Graphics Array) is a video standard which is an industry base standard. It supports 320x200 resolution at 256 colors, or 640x480 at 16 colors.
Virtual Memory   A file on a hard disk, known as a swap file, which behaves like memory when needed.
VM   VM (Virtual Machine) - a self-contained operating environment that behaves as if it is a separate computer.




WAN   A Wide Area Network, such as a network which spans the U.S. Usually comprised of 2 or more LANs.




XMS   XMS (Extended Memory) is the memory above 1088k which is used for DOS programs requiring more than memory than available in conventional memory.
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