Computer Definitions

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These are not in alphabetical order, but in an order to help you try to better understand your computer system as you get into it. These are not any official definitions but they are my terminology used for my classes.

Computer System: Consists of Computer, Monitor, Keyboard, Mouse, Printer, and Surge protector. It may also consist of a scanner and other optional devices.

Selecting a Computer: See separate document but understand difference of clone and manufacturer specific computer below.

Clone: The term clone came about early in the computer evolution when the Japanese copied the original IBM XT and following generations. The Chinese soon joined in this cloning. Clones were usually half the price of the actual IBM computer. They were usually equal or better in quality and features. Clones quickly caught on and competed with IBM's original design. They had the same size motherboard and mounting holes as the original IBM's and the keyboard and power connections were the same. Also the slot spacing was the same. A clone motherboard would fit in an actual IBM XT or AT case for repair or upgrade. This also became known as a "generic design". Presently, as of this writing , over 200 manufacturers of clone motherboards have outsold all other name brand manufactures combined including IBM, Compaq, Dell, Gateway, Packard Bell, Sony, HP, and many others. Clones are not generally advertised. They usually sell themselves as they are usually of much higher quality than most "mass manufactured highly competitive and low cost" computers today. Motherboards for clones are called "generic" because of the standard size, mounting, standard connections, and ability to interchange between the various generic designed boards and cases. Generic motherboards do not fit in manufacturer specific cases from major manufacturers. Designs from the 286, 386, 486, and Pentium use the "AT" design. Pentium II and Pentium III use the "ATX" design. An ATX motherboard does not fit in the AT case, and visa versa. The are many reasons for this.

Compatible: Refers to any computer that is usually software compatible with the PC type computers, but not necessarily hardware compatible. This usually refers to "Manufacturer Specific Designs". Most major manufacturers of computers including IBM, Compaq, Dell, Gateway, Packard Bell, HP, Sony, and numerous others, design computers where their system motherboards are designed of a size and shape that no other main motherboard will fit in that case. When it comes time to repair (replace the motherboard) or upgrade, no other board will fit in place except that manufacturers board. The manufacturer can charge whatever they please including board exchange prices typically upwards of $600 or more.

Computer Box or CASE: Contains the system motherboard, power supply, floppy and hard drive, expansion cards. May also contain CD ROM drive and a backup device such as a tape drive or zip drive. See also items below for explanation of these items.

Monitor is a television like device to display the operations of the computer. There are several generations that may not be compatible with each other.

Printer: Device to give paper print out from the computer of documents you create. There are several types including thermal, daisy wheel, dot matrix, ink, and laserjet. Ink is the post popular because of its low cost.

Keyboard: A typewriter like device to type letters and numbers as well as punctuation marks into the computer. Older PCs and XTs used a keyboard that will not work with newer computers, even though the connector is the same.

Mouse: Hand sized device that is moved around on the desk to control the pointer on the display monitor.

Joystick: Game device used for games where left to right, forward to reverse, and push buttons are used to control direction and speed as well as fire weapons and drop bombs.

Motherboard or Main System Board: Contains the main processor chip or CPU, main system memory, BIOS, CMOS, Clock, Battery, Chipset, Expansion Slots, Keyboard Connector, Power supply connector, control panel connectors, jumpers, and other support circuits.

Power Supply: A sealed box within the computer case that converts 120 volt AC into 5 and 12 volts DC for the computer boards and drives. This should never be opened because of dangerous shock hazzard. There are no user servicable parts or fuse.

CPU: Central Processing Unit or processor (a integrated circuit chip) that is the main brain of the computer such as a 386, 486, or Pentium.

Expansion Slots: Slots where you can plug in optional cards from various manufacturers such as the display card or interface, modem, network card, sound card, and sometimes drive controllers and extra ports.

Expansion Cards: Any card that plugs into an expansion slot. Expansion cards give flexability to change to new technology or replace defective cards.

VLB: VESA Local BUS expansion slots are one common standard 32 bit slot used for higher performance display cards and controllers of 386 or 486 computers. There were some other less common local bus slots including proprietary 32 bit slots.

Opti Local Bus: 32 bit bus designed by Opti that never became a standard.

EISA Slots: Extended expansion slots that offered some higher performance in an attempt to increase performance with a competing standard. This standard appears to be close to dead.

Microchannel Slots: An IBM Proprietary standard expansion slot used in IBM PS2 computers and some other ones licensed by IBM.

PCI Slots:Peripheral Control Interface or PCI is the new interface used on Pentium motherboards that has a 32/64 bit interface to the bus.

AGP Slot: New display card slot with faster access to the computer bus.

System Memory: The memory chips that hold the program and data while you are processing. This is temporary memory and it only holds information while the computer is on. Typically, it is 640k, 1M, 4M, 8M, 16m, 32M, 64M, or 128MB.

BIOS: One or two computer chips that has the first computer instructions that test and start the boot process of a computer. It can also be a chip on a controller card that has instructions for that card. The last instruction of the BIOS is to look for an operating system on either a floppy or hard drive.

CMOS: The memory where the computer's configuration is stored including date and time, how many and what type of floppy drives, the hard drive geometry, how much system memory, and the type display card. Many times other boot options as well as timing options are set and stored here. This CMOS is usually part of a "chipset" rather than an individual chip. This memory is kept alive by a battery which usually dies and leaves your computer inoperative after several years of age. What CMOS stands for has nothing to do with what it actually is (complementary metal oxide semiconductor). Sometimes, this chip is separate and removable such as the "Dallas Clock". It is also possible that a memory conflict can change or wipe out the CMOS information.

Real Time Clock: Part of CMOS. Keeps date and time.

Setup: A program that controls access to the CMOS or real time clock for configuration that can be software or firmware. Many newer "setups" are accessed by a keystroke such as hitting the DEL key, F2, or Control Alt ESC or S just before the computer boots. Note that the information in setup or CMOS is critical and that if accidently or otherwise changed, will render the conputer useless. Specific setup information should be recorded near or on the computer - specifically the hard drive cylinders, heads, and sectors per track.

Hard Drive Geometry: Specific cylinder count, head count, and sectors per track of your hard drive as it was set up. These numbers may not be exactly the physical numbers of actual components, but a translated set of numbers that the computer can work with. It is also possible that different combinations of numbers could be used other than the ones intended, a technicians choice when originally set up, and that specific set must be used when the battery dies or you will not be able to get to your programs or data if that alternate set of numbers was used. These numbers can be autodetected in newer computers in the CMOS setup.

Clock: Your computer has an internal clock signal , a signal generator, that drives the processor, bus, and other components that determines how fast data is transferred or how fast something happens. This clock drives the processor at a given speed. An original PC or XT computer had a clock of 4.77 MHZ while the latest computers have clock speeds of 100, 133, 166, and 200 MHZ. The clock speed and the BUS width determine how powerful the computer really is. System Memory: Memory chips that store information including the operating system, programs, and data as you use the computer and it is processing. All information in these chips is gone and lost when the power is turned off.

Control Panel: Usually a group of switches and lights on the front panel of the computer case that allows the user to control some functions and determine status of other functions. Typically: a reset switch, a turbo switch, a hard drive light, a turbo light, and a power on light. Sometimes a keyboard lock.

Turbo Switch: A push botton switch on many computers used to slow down the computer or put it in its normal high speed. The switch should normally be on for fastest processing. Most Pentium computers no longer use this.

Drive Bays: Openings in the computer case for floppy, hard, CD Rom, and tape drives. Cases come with 1 to 8 drive openings and you should plan how many you need in the future if you have that option. There are 3 1/2 inch and 5 1/4 inch openings. These include internal bays for internal hard drives.

Openings: Drive bays may or may not open to the outside. If you want a 3.5" and 5.25" floppy, a CD ROM drive, and a tape drive, you need at least 4 external openings.

Power Supply Connector: This connector is on the motherboard where the power supply connects to the motherboard. Care should be taken to make sure you do not accidently unplug this if you are working inside and particularly not reverse these connections if you should accidently pull them off. The power supply supplies several different voltages to the system board and drives. There is +5, -5, +12, and -12 in addition to common and power good signals.

Power Switch: A switch to turn on and off the AC Power. The AT design actually switches AC power on or off. The ATX design on newer computers uses a "soft switch" that electronically shuts off the computer, but doesn't actually shut off the AC 120 volts. It works on a momentary pulse to turn on or off the computer. The supply is actually always on.

Jumpers: Little wire jumpers that can be changed on the motherboard and expansion cards to determine features and addresses of ports and interfaces.

Keyboard Connector: This is where the keyboard plugs into the motherboard and is usually in the rear center of most computers. There are 2 type plugs, the standard AT type and the PS2 type which is smaller.

Chipset: Refers to specific manufactured chips that contain what used to be hundreds of individual integrated circuits chips on a motherboard that have been combined by certain various manufacturers to give a personality to the computer including specific features.

BUS: A parallel path thru the computer in which groups of bits are passed from the processor to memory and expansion cards or other components of the computer. The original PC or XT was an 8 bit computer where 8 bits of data were passed from the processor to memory and expansion cards at one instance. The 286 AT computer was a 16 bit computer where twice as many bits were passed at any one instance. This made for a computer that was twice as powerful as an 8 bit computer. The 386 and 486 computers were 32 bit computers. The processor and memory passed data at 32 bits per clock cycle or instance. There were some low cost computers that had 386 or 486 32 bit processors that addressed memory at only 16 bits and they were not as efficient. The Pentium is a 64 bit computer and it should address memory and the rest of the computer with a 64 bit parallel path. Some manufacturers do not do this. A non Intel 586 processor (64 bit) is sometimes found on 32 bit 486 motherboard by some computer manufacturers to try to compete with Intel's Pentium. Although some diagnostics show remarkable processing power, they still do not stack up to the real Pentium, overall. These 586 chips do have some performance gain over the 486.

Floppy Drive: A device that reads a floppy disk that is used to install programs or save data from the computer. Typically, a floppy disk today holds 1.44 MB of data on a 3 1/2 inch disk. There is also an older 3 1/2 inch 720K disk that isn't used much anymore and an even older 5 1/4 inch 1.2 MB or 360 K drive and disk that is obsolete. 720K and 360K are referred to as DSDD or double sided double density while 1.44M or 1.2 M are referred to as DSHD (double sided high density). There is also a 3 1/2 inch 2.88 MB EHD (extra high density disk). The EHD is not common. A new format called LS-120 holds 120 MB on a special disk, but also reads the 1.44 floppy.

Hard Drive: A disk drive that is normally sealed (fixed), internal to the computer, that stores the operating system, programs, and data. The computer loads the operating system (boots) from the hard drive into system memory, and then loads programs that are stored on the hard drive into the system memory so the computer can use the program. See more details below.

CD ROM Drive: Similar to a audio CD for music, these disks store about 680 MB of computer programs or 74 minutes of music. They are normally read from and not written to. There are several compatibilities over the last years and older CD ROM drives may not read certain newer formats. CD ROM drives are rated 2 ways, first by data transfer rate and secondly by access speed. 2X refers to twice the rate of 150KB per second and 8X refers to 1200KB per second. There were several generations before the 150K transfer that were even slower. As of this writing, 32X and 40X are fairly common CD ROM drives, with faster ones promised. Access speed is also quite importance but most forget that this is important to. Under 200 MS access is good with lower numbers even better. A CD ROM recorder can be used to make single CD Disks.

DVD Drive:A newer type of CD ROM drive that also holds up to 4 GB or more of data including a full length digital video movie. There are several formats including "DVD" digital versital disk, single sided and double sided, and 4 GB to about 17 GB of data storage.

Display Card: Usually an interface card that plugs into the motherboard that contains circuitry to interface to the display monitor. SVGA and VGA monitors use a 15 pin high density connector to this card. Some low cost computers do not have a separate card, but have the display circuitry integrated on the motherboard, a BIG mistake.

Modem: Device that connects to the computer in an expansion slot or external to the computer on the serial port that is used to convert digital data to a signal that can be used on a phone line for communications.

Sound Card: A card that plugs into an expansion slot that picks up digital sound from the software and computer bus. It can also digitize sound to record into the computer. There are several different sound standards and there are several different sound card manufacturers with their own different cards to make this happen. A company called Creative Labs has the standard that others try to copy. We recommend only using the actual Sound Blaster 16 serial of cards to avoid any software problems or incompatabilities. Note that the SB32 is not a 32 bit card, but a 16 bit card with 32 voices. There are also two distinct audio methods of storing music on a CD, the one used as a music format such as what you buy in a music store and a digitized method that a sound card picks up. A cable between the CD ROM drive and the sound card combines these sounds.


Hardware: Physical computer equipment such as the computer, monitor, printer, keyboard, a controller card or any expansion card, cable, memory chip.

Software: A computer program, the data you create, the operating system, or a device driver.

Firmware: A Computer program in a chip

Chip: A integrated circuit module containing more than one, up to thousands of transistors. They are used in a computer or other electronics devices.

BIT: A single 0 or 1. Computers only understand 1's and 0's at their lowest level of computing.

BYTE: A group of 8 bits is called a BYTE. Sometimes, a byte is also called a "word". It can represent a letter or number as well as instructions within the computer.

KB: Kilo is 1000 or 1,024 bytes exactly.

MB: Mega is 1,000,000 or 1,048,576 bytes exactly.

GB: 1 billion bytes.

HEX: A specific numeric counting system that computers use to count and address various memory locations in the computer. Counting in hex is 0 1 2 3 4 5 6 7 8 9 A B C D E F which is 16 bits.

Operating System: Software instructions that load after the BIOS instructions that load into the computers memory to prepare the computer to operate with other software and the components of the computer. DOS (disk operating system), Unix, OS2, Windows 95, or Windows NT are examples of operating systems.

Programs: Software instructions that load into the computer's memory from a floppy or hard drive (or CD ROM drive) that allows the computer to perform a task or tasks such as word processing or data base management.

DATA: The information you create including letters, spreadsheets, and mailing lists.

Driver: Software used to interface hardware with software. Because there are numerous manufacturers making various models of computer components used with computers and all having different features, software is used to tell hardware how to use the add on devices. Mouse', display cards, printers, scanners, sound cards, CD ROM drives, and modems are examples of devices requiring these drivers.

File: A program or data containing information. Configuration files:Simple computer files containing data as to how a computer or programs are set up. Word Processor: A program that takes typed data and formats it so it can be manipulated.

Text Editor: A simple program to type words into a computer file without any fancy formating.

Spreadsheet: A program that manipulates rows and columns of data. This can do mathmatical functions that may be programed into it. Data Base:A program to manage information such as names, address, phone numbers, and other data about persons or companies.

Utilities: Computer programs that do maintanence functions or otherwise manage other programs on your computer.

Multi-media: A term used to describe a computer having a CD ROM drive, a sound card, a display card with at least 256 color capability, a large hard drive, and a fast processor.


Booting: The process of the computer turning on and preparing itself for use including the loading of the operating system.


Conventional Memory: Only the first 640 K of your computer is called conventional memory, no matter whether you have only 640K or 32 MB of memory in your computer. This is a key area and it must be managed or set up properly for your computer to function properly.

Extended Memory: The amount of memory above 1 MB of system memory typically reaching 8, 16, or 32 MB, although certain special applications may require additional extended memory beyond these numbers. Windows knows how to use this extended memory to the fullest extent.

UMB Memory: The area just above 640K to the 1 MB point is special because there are barriers and blocks used for certain devices. There are also some open address blocks within this area. The display card uses one or two blocks, your hard drive controller uses another block, and the system BIOS uses another. Additional controllers or devices may use additional blocks of this memory. Each has a specific address range. Memory managers can usually use these vacant addresses to load certain software drivers into them.

Expanded Memory: Managed memory set up by a memory manager for certain software that uses this type of memory. It pages it by blocks into a vacant UMB.

SIMM: A common type of memory module for system memory. A SIMM can be a 30 pin, 32 pin, 68 pin, 72 pin, or other pin conbination printer circuit board containing individual memory chips. Although many computers use standard SIMM modules, there are some very popular named computers that use proprietary SIMM modules and you must use the proper modules for that computer. Memory must also be installed in banks. SIPP: An older memory module similar to a SIMM, but with wire leads.

BANKS: Memory banks are a specified number of memory modules to make up a ligitement group so the computer recognizes the memory. For instance, a 486 processor is a 32 bit processor which addresses memory at 32 bits at a time. It takes 4 30 pin SIMMs to make up a 32 bit path to the processor since the 30 Pin SIMMS are each 8 bit. Some cheaper 486 computers use only 2 modules and have only a 16 bit path to the processor. Pentiums are 64 bit machines and to operate most effeciently, require 2 72 pin SIMMs as these 72 pin SIMMS are each 32 bit modules. RAM Randon access memory usually refers to individual system memory chips although it can describe system memory as a whole.

CACHE Special very high speed memory chips in quality computers that store certain memory instructions that may be repeated frequently. This memory is located close in circuitry to the processor and most times in it and can speed up performance significantly.

VRAM Special memory on the display card that determines how many colors and at what resolution the display card is capable of. Virtual Memory: Simulated system memory allocated as space on a hard drive. Expansion Slots: Slots on the motherboard in which expansion cards can be plugged in to. There are 8 bit, 16 bit, 32 & 64 bit slots and there are several standards that the card must adhere to for that computer. The bigger the bit path to the slot, the more effecient the card may be capable of. See next definitions. ISA Slots: Standard 8 and 16 bit slots found on most computers other than IBM PS2 series or EISA computers.


Parallel Port: Your computer has a parallel port on the rear which is used to connect to a parallel printer. It is a 25 pin female jack or connector and usually the computer has only one, although additional ports can be added. There are also external tape drives, hard drives, and CD ROM drives that can also be connected to the parallel port if they are so designed.

Serial Port: Your computer usually has 2 serial ports as standard. One is sometimes used for a mouse connection and the other is sometimes used for an external modem. Many modems are found inside the computer, rather than externally.

Game Port A port (15 pin) used in gaming to connect a joystick. An analog device rather than digital device. Usually found on a sound card.

USB Port: Universal Serial Bus is a new serial port just being released for future use to outdate the present system of serial and parallel ports and to give a faster interface for future faster modems and other devices. It will also connect mouse', keyboards, and printers.

PS-2 Mouse Port: Special serial port connected to the motherboard bus that uses different resources than the real serial ports. It also has a special small round "Din" connector.

Bus Mouse Port: A special mouse port that is on an interface card that is different than the PS-2 mouse port. Rarely used any more.


Parallel: A method of transferring data in groups of 8 bits at one instance of a clock cycle.

Serial: A method of transferring data one bit at a time, followed by another bit and another, etc.


ADDRESSES: Most expansion cards and onboard devices in the computer communicate with the processor and other parts of the computer on address lines and get attention of the processor on Interupt (IRQ) and DMA channels which must be unique to the various devices. Groups of addresses are reserved for various functions.

Serial ports use addresses of hex 3f8, 2f8, 3e8, and 2e8 in that order. Serial ports use IRQ channels 4 & 3 and are shared. Serial port 1 shares the IRQ of port 3 and 2 shares the IRQ of port 4. If you have a serial mouse on Com 1, you can NOT have a modem on Com 3 unless you go to a non standard IRQ. Newer modems allow different IRQ channels to avoid some conflicts but software must also comply.

Parallel ports use hex 378, 278, and 3BC and IRQ channels of 7 and 5. A third LPT port has to be shared.

CD ROM drives and sound cards must also be properly configured and conflicts between any address, IRQ, or DMA channel can bring a computer to a halt. CD Rom drives and sound cards can use many different addresses and you must be carefull that you do not conflict with other devices.

Plug & Play: Plug and play is supposed to make life easier by letting the operating system set addresses for various cards instead of setting switches or jumpers on cards. In reality, it usually doesn't because plug and play addresses are changed by software and software conflicts change them with out your knowledge. Just re-plugging in a PNP card can change its address.

IRQ Channels

IRQ 0 System Timer

DMA 0 Memory refresh

Some Common Addresses Addresses

01F0 Primary hard drive controller (HDC)

0170 Secondary HDC

01E8 Third HDC (usually on a sound card for CD ROM)

0168 Ch 4 HDC (usually on sound card for CD ROM)

0200 Game port

03F8 Com 1

02F8 Com 2

03E8 Com 3

02E8 Com 4

03BC Old LPT 1 or LPT 3

0378 New LPT 1

0278 New LPT 2

0220 Sound

0330 MIDI

0388 Music Synthesizer

0360 Network

3A0 SDLC Bis 1

380 SDLC Bis 2

3DO CGA adapter

3F0 Disk Drive Controller

0F8 Math Coprocessor

0F0 "

0F1 "

000 DMA Controller #1

0C0 DMA Controller #2

020 Interupt Controller

0A0 Interupt Controller #2

040 Timer

060 Keyboard Controller

070 Real Time Clock

080 DMA Page Registers

Controller: usually refers to the floppy and hard drive controllers which may be on an expansion card or on the motherboard. Pentiums with plug and play require the controller to be on the motherboard so that the mother-board BIOS can configure them. Pentiums usually also have a secondary IDE hard drive controller for additional drives beyond 2 hard drives or CDROM drives.

Hard Disk Drive: A fixed disk of a given capacity that normally does not have removable media used to store the operating system, programs, data, and utilities. Recording/playback heads glide over a cushon of air above magnetically coated platters inside this sealed unit where air, smoke and dust is sealed out. While operating, a hard drive is very delicate and should not vibrate or get banged as the heads should never come in contact with the surface of the platter. Older hard drives of 10, 20, 30, 40, 65, or 80 MB capacity used an interface and controller called MFM or RLL which is not used any more making them obsolete and unreplacable. IDE hard drives are usually 100 MB and higher in capacity with the newest EIDE drives from 1 to 20 GB in size and larger as well as much faster.

ESDI: Almost obsolete high performance and expensive type of interface between a hard drive and controller.

SCSI: "Small computer systems interface" type of interface for hard drives, CDROM drives, scanners, tape backup drives, and other equipment. 7 devices can exist on a standard SCSI interface. (much more expensive)

IDE: Refers to the type interface between the hard drive or CDROM drive and their controllers. There are also other type controllers, either of older technology or for different needs. Only 2 drives, a master and a slave can connect to an IDE controller.

EIDE: A newer version of the IDE interface for higher performance.

Utlta 66: High performance hard drives used on an IDE controller and computer that is ultra 66 capable.

Ribbon Cable: Usually the cable that connects floppy, hard, CD ROM, and tape drives to their interface controllers. Floppy drives use a 34 wire ribbon cable while IDE drives use a 40 wire cable. SCSI uses a 50 wire cable.

Hard Drive Preparation: Series of steps to prepare a hard drive for use: Low level format, partitioning, high level format, installing operating system

Internal components of hard drive:

Platter: Flat round magnetically coated disk inside a hard drive which stores data.

Head: Recording and playback heads that mount on an arm and slides back and forth over the platters to transfer information.

Track: An electronic concentric circle on the platter. There are hundreds of these tracks on each side of each platter.

Cylinder: The total number of all tracks on all sides of each platter in a hard drive.

Sector: An electronic division or grouping of each track. A sector is 512 bytes in size. Data is stored in these sectors.

Cluster: Group of sectors. May be 4K, 8K, 16K, or 32K in size

Addresses: There is an electronic address at the start of each sector so that each sector can be found.

FAT: File allocation table: An address collection of each sector and which data is stored there including which addresses are available.

Low Level Format: First step in preparing a hard drive. An IDE hard drive should only be low level formatted at the factory. This is a process where tracks of information on the hard drive platter are divided up into sectors and addresses are placed in front of each sector.

Partition; The process of writing information to the hard drive in which is stored how the drive may be divided, which operating system is used on it, and some other necessary informatio.

Partition Table:Information about how the hard drive may be divided and the DOS version as well as which partition is bootable.

Master Boot Record:A record of information called BIOS parameter block or BPB immediately after the partition table that has the cylinder, head, and sector information as well as cluster and directory size. It also runs a bootstrap program to load the main operating system.

Format: DOS format verifies addresses and builds a file allocation table om the hard drive. This format on a floppy disk also places these addresses on each sector.

Directories/Folders: DOS allows the creation of additional directories or folders from the main or root directory to group files, similar to file folders in a file cabinet so files can be organized. Each program or group of files for a program should be stored in its own directory.


Tape Backup Drive that backs up hard drive data onto tape. These drives do 40, 120, 250, 350, 800, and 3 or 4 GB and more of backup data.

Surge Protector: A device that protects electronic equipment from damaging high voltage spikes over the power line or phone line. Computer chips typically use 5 volt devices and anything much over 5 volts will damage them. Surges can come over phone lines and cause extreme damage to computers because these overhead wires act as antennas and pick up stray electricity induced into them similar to the way a transformer works. UPS or Uninteruptable Power Supply is a battery power pack that typically operates your computer during a short power outage or long enough to shut down any software that may be in use. Many programs can not cut off without properly closing them down without causing data loss and program crashes.

Backup: Data loss can be inconvenient or costly. Computer failures happen for various reasons including component failure, human error, power interuption, software conflict, virus, or other reasons. If you create or obtain data, back it up to other sources including floppy disk, tape, or other means including keeping copies at another location because of fire or theft.

Virus: A program created by a computer programmer that causes damage or annoyance to a computer user. Contrary to popular belief, they do not grow out of no where nor are they picked up from human diseases short of warped mines. They are spread by sharing floppy disks or received over a modem

Common Connectors:

DB25 Male D shapped 25 pin connector used for serial or parallel connection.

DB9 Male D shapped 9 pin connector used for serial connection.

DB9 Female D shapped 9 pin connector used on Digital RGB Mono, CGA, and EGA.

HD DB15 D shapped high density connector used for the analog VGA monitor connection

DB15 D shapped 15 pin connector used for joystick game device.

DIN Round connector with several sizes and pin configurations for keyboards and mouse connections

Centronics Larger D shapped 50 pin Connector with an island like center where the connections are made.

Male Connector with pins sticking out

Female Connector with socket for male pins to insert into

NOTE: The difference between the 9 & 15HD video connections is so you do not plug the wrong monitor to the wrong card or visa versa - damage to the monitor and card will most likely result).

Video Display: This is usually an expansion card that plugs into an expansion slot so you can upgrade or replace the card should it become necessary. Newer cards for Pentium computers are PCI bus for higher performance. You can also get accellerator cards for special applications that can speed up graphical performance. See additional information later on in this document.

8 BIT Video cards were a standard in monochrome, CGA, EGA, and early VGA video cards. They are rarely used except in the remaining older computers.

16 BIT VGA Video Cards are still around in 386 and 486 computers. Many do not work in or will slow down a Pentium computer.

PCI VGA cards are the standard in Pentium computers because they allow more display information to be passed from the computer bus to the display card faster, 32/64 bits at a time.

AGP A new very fast video bus, connector, and display card found on the latest Pentium IIs.

Video Memory: Memory on the video card that determines what resolution and how many colors are displayed at that resolution. 1 MB of Display memory is a minimum in multimedia computers. Typical memory numbers are 256K, 512K, and 1 Meg of memory in older cards. Newer cards can come with 2, 4, or 8 MB or memory on the display card. Most people don't need the higher amounts.

Raster The scanned lines, blank or information, on the monitor screen.

Scan lines: Three electron beams, red, green, and blue, are electro-magnetically generated and controlled by the picture tube in the monitor to scan across the picture tube in a perfect line starting at the upper left and going across to the right, then turning off and going back to the next line, turning on and scanning the next line down from left to right,eventually ending up at the botton and starting over. The red beam is aligned to hits red dots of phospher on the screen as is the green beam aligned to hit the green dots of phospher, as is the blue beam aligned to hit the blue dots. The 3 beams change intensity extremely rapidly as needed to lite the correct phosphers and show the intended image on the screen.

Resolution: The number of vertical and horizontal scanning lines displaying the image determine the resolution. Display cards and monitors can operate in various modes as shown in a chart below. The higher the resolution, the more detailed the image but also at a smaller size.

Diagonal Monitor screens are rated by diagonal measurements in inches which is the picture tube size and not what you actually see. A typical 14 inch monitor can be 12.5 to 13 inches in actual usable diameter.

Dot Pitch:The smallest combined dot of a red, green, and blue phospher. The smaller the dot, the better the quality. It is a metric measurement in millimeters. The acceptable dot is .28 millimeter for a 14 or 15 inch monitor. Larger dot sizes of .31, .39, .41, and .52 are not acceptable for high quality SVGA today. Beware cheap monitors! They are still around and some are not what they are marked as. You get what you pay for. High quality 17 & 20 inch monitors should have a dot pitch of .25 or .26.

NI or Non Interlaced:Non-Interlaced refers to a scanning lines 1,2,3,4,5,6,7, 8,9 and so forth down to the bottom in order on the monitor. In cheaper monitors, Interlaced scanning at 1024 resolution takes place meaning lines are scanned every other line 1,3,5,7,9, and all odd number lines to the bottom, returning back to the top to scan lines 2,4,6,8, etc to the bottom of the screen and then starting over. This is a poorer quality, but is also standard on all regular television sets.

RGB RGB or Red, Green, Blue, means the video signal is carried as 3 separate colors, red, green, and blue from the display card to the monitor. This a standard with computer monitors. RGB can be carried in 2 forms to confuse you more: Digital and Analog.

Composite:Combined red, green, and blue video information combined with sync signals over a single shielded wire as in a TV to VCR connection. Some older computers such as Apple & Commodore used a composite connection.

NTSC National television standard sync signals used in America as opposed to PAL standards in Europe.

RF A low power radio frequency signal used to carry a video signal from one device to another connecting to the antenna connection as in TV channel 2, 3, or 4 from the computer to the monitor.

Mono Black & white or green or amber (one color) monitors or display cards used before color became popular.

Hercules A manufacturer who created a high resolution monochrome standard.

CGA The first IBM color computer standard with 4 colors and low resolution. CGA is color graphics adapter.Now considered obsolete. EGA Enhanced color adapter, 16 colors and a better resolution over CGA.

PGA Professional graphics adapter, a try at a standard that didn't make it.

VGA Video graphics array is the latest color standard presently used that works in 16, 256, 32,000, 64000, and 16 million colors. It is also backwards compatible to CGA and EGA scanning resolutions. Its basic mode is 640 by 480 line resolution with 16 colors, even if you have a super vga card and monitor. Software drivers are required to place display cards into extended resolutions and higher color modes. The term super vga or svga has changed over the years and unless you specify specific resolutions, you are not sure what you expect. You rarely use 800 by 600 or 1024 by 768 line resolution unless you\ have specific need as the information on the screen gets very small. The capability of running 16 million colors at 640 by 480 lines and 256 colors at 1024 by 768 resloution is usually desired in todays systems.

SVGA Extended resolutions usually referring to resolutions 800 by 600 and higher but also referring to 640 by 480 at 256 colors. Different manufacturers have different definitions and you should not assume you have a specific SVGA product because SVGA was used to describe it. You should know what you want in resolution and colors.

8514A An IBM VGA mode and refers to their monitor model number. XGA IBM's term for their high resolution standard. Not normally used by other manufacturers.

UVGA Unofficial term for resolutions of 1280 by 1024 and higher but some manufacturers have used this for much lessor resolutions.

Accellerator: Display card with video processors to speed up graphics information getting placed on the screen.

NTSC Converter: A box or circuit on a card that converts VGA information to standard TV scan rates so it can be recorded or displayed on a big screen TV.

MULTI-SYNC or MULTI-MODE refers to monitors that switch or can be switched with the various video standards. NEC made a 3D that did CGA, EGA, and VGA without switching a switch.

SOFTWARE DRIVERS: Each video card comes with a disk of software drivers. These are small programs that are loaded into Windows or into a DOS application program to make them compatable with your video card and program. DOS programs usually run without drivers unless you need special resolutions, but some Windows programs need higher color modes to make them work, such as the 256 color mode.

MAGIC COMBO:A manufacturers special video cards that can do monochrome and color meaning that you can switch between a mono monitor or CGA color monitor with the same card. It can also run CGA color graphics on a mono monitor if switched properly.

SPECIAL NOTES If you have a EGA Card, You can NOT use a CGA Monitor and visa versa except under some instances with only a few special monitors that will do both. BEWARE if you have a VGA Card and or a VGA Multisync Monitor that is switchable between digital and analog. If the switches are set wrong, you can do damage to either the card or monitor or both that would not be covered by warranty.

Some Common Video Specs in Chart Form

Mode, Resolution, Colors

MDA 80 Col x 25 Row

Hercules 720 x 348 lines

CGA 640 x 200 or 320 x 200 (4 colors or shades)

EGA 640 x 350 or 640 x 200 or 320 x 200 (16 colors or shades only)

VGA 640 x 480 (monochrome mode/monitor)

VGA 640 x 480 (16, 256, 32,000, 65,000, or 16 million colors)

SVGA 800 x 600 (16, 256, 32,000,65,000, 16 million colors)

CGA .52

EGA .42 or.39

VGA .52, .42, .39, .31

SVGA .52, .42, .39, .31, .29, .28, .27, .26, .25