Glossary of Microcomputer Terms
Absolute Error - The sum of all the individual sources of error for an analog-to-digital converter. Absolute error is usually expressed as a percentage of the measured reading + one bit of resolution.
Acoustic Coupler - A type of modem that connects to the telephone handset in two rubber cushions so that sound gets to and from the modem without any direct electrical connection.
Acronym - A word made up of letters from other words. For example, RAM is an acronym for Read-Only Memory.
Active Cell - The cell where the cursor is located in an electronic spreadsheet.
ADC or A/D - Analog-to-digital converter. A device that converts an analog signal (voltage, current, etc.) into digital data that can be interpreted by the digital electronics of a computer.
Address - A number used by the CPU to specify a particular memory location.
Alphanumeric - A word made from alphabetic and numeric. It stands for any data that contains numbers, letters of the alphabet, and other commonly used symbols such as $, %, and @.
Analog Signal - A signal that is capable of being continuously varied.
Application Software - Software written to perform a specific task such as a word processing, spreadsheet analysis, or database management.
Argument - The data or expression that a function evaluates. In this example, X is the argument for the LOG function: LOG(X).
ASCII - American Standard Code for Information Interchange. This is a method of encoding alphanumeric characters and control sequences so that information transmitted by one computer can be understood by another. There are 127 characters currently defined by the ASCII code.
ASCII File - This is sometimes referred to as a text file. This is a data file in which each character of the data is stored as its normal ASCII equivalent.
Assembler - A program that converts assembly language instructions into machine language.
Assembly Language - A low level programming language that uses a set of mnemonics to give instructions to the computer. An assembler converts these mnemonics to machine language.
Asynchronous Transmission - A form of data transmission in which the interval between transmitted characters is not equal. Typing (for most people) is a form of asynchronous transmission of data to the computer.
Autoexec.bat - A file that is read by DOS when the computer is first started. This file contains commands that the computer automatically executes.
BASIC - An acronym for Beginner's All-Purpose Symbolic Instruction Code. This is a high-level programming language developed at Dartmouth College in 1965.
Baud - A measure of the speed of transmission of data to or from a computer. The baud rate is roughly equal to the number of bits of information transmitted per second. It is not a direct measure of data transfer because some of the bits that are sent are used for control and parity checking.
Baudot - A 5-bit binary data coding scheme.
Bit - An abbreviation for binary digit. This is the fundamental unit of information used by a computer. It is often represented as a 1 or 0, but the computer recognizes it as one of two possible states (on/off, +5V/-5V, etc.).
Bits-per-second - Abbreviated bps. The number of bits that are transferred in one second by a computer.
Boot - Boot is short for bootstrap, as in "pull yourself up by your bootstraps". It describes the process by which a computer or computer program starts itself up. To boot a computer or a computer program is to start it. The information a computer needs to boot itself is contained in ROM.
Boot Record - A machine language program located on a disk that contains the instructions for loading DOS into RAM.
Bubble Sort - A sorting technique where each number is compared to the number that follows it, swapping the two numbers if one is large (or smaller, depending on the direction of the sort) than the other. This process is repeated until no more swaps can be made.
Buffer - A storage area in RAM memory for information that is not going to be used right away but which needs to be kept together. Data comes out of a buffer in the same order that it went in, so buffers are used for storing data that will not be processed immediately. Buffers are used for handling data that is coming to or from a disk, transmission line, or printer.
Bug - Either an error in the hardware or in the software. Software bugs can either be due to typographical errors, incorrect syntax, or faulty program logic.
Bus - A group of wires along which travel the signals that go from the CPU to or from I/O devices.
Byte - A unit of memory storage or data that is typically 8 bits long. An 8 bit byte can be used to represent any number between 0 and 255. Normally, one byte will hold one character of data.
Cell - The intersection of a row and column in an electronic spreadsheet.
Centronics - The industry standard parallel printer interface.
CGA - Color Graphics Adapter. Maximum resolution is 640 X 200.
Character - Any single letter, number, punctuation mark, etc., that can be typed from the keyboard, put on the screen, or sent over the communication line.
Chip - (See DIP.) A small piece of silicon containing a large number of electronic circuits. Usually this piece of silicon is packaged in a plastic case with wire leads extending from it. This entire package is sometimes called the chip.
Clock - An electronic device (usually crystal controlled) that sends out a timing signal to synchronize the operations of the computer.
Clone - A computer manufactured by one company to operate like a computer from another company.
Cluster - A collection of sectors. A cluster is the smallest amount of storage space allocated to a file.
Compiler - A program that converts another program that was written in a high level language into assembly or machine language. The program before it is compiled is called the source code. After the program is compiled, it is called object code.
Command Processor - The portion of DOS that accepts commands and executes them. The command processor contains the internal DOS commands.
Composite Monitor - Either a monochrome or color monitor that works with signals much like those used by an ordinary television. The resolution of a composite monitor is not as good as that of the corresponding RGB or TTL monitor.
Concatenation - The process of adding strings together. An example of concatenation would be adding two words together to produce a single word: "kilo" + "byte" = "kilobyte".
Config.sys - A file that is read by DOS when the computer is first started. This file contains information about the hardware configuration of the computer.
Coprocessor - This usually refers to a math coprocessor which is a chip that handles arithmetic operations in hardware instead of software. This greatly accelerates the speed of math intensive software if the software is written in a language that can address the math coprocessor. The math coprocessor that corresponded to the old 8088 CPU was the 8087.
CPU - Central Processing Unit. This is the brain of any computer. The CPU performs all the arithmetic and logic operations of the computer. A microcomputer has the CPU on a single chip.
CRT - Cathode Ray Tube. This is the most common output device for microcomputers. It is also called a VDT (video display tube).
Cursor - The on-screen character that indicates where the next action from the user will take effect.
Cylinder - a term related to disk storage. A cylinder consists of all the same numbered tracks from all the surfaces of a floppy or hard disk.
DAC or D/A - Digital-to-analog converter. A device that converts digital data from a computer into an analog signal.
Database - A collection of files. Sometimes the word database is used to mean a collection of records (see file).
Data File - A set of data saved to tape or disk under a single name.
Data Word - A character as sent over the communication line. It consists of a character up to 8 bits in length, together with a start bit, a stop bit, and possibly a parity bit.
DBMS - Data Base Management System. This is a program that manages large amounts of data and allows for retrieving data and writing reports based on indexes.
DCE - Data Communications Equipment.
Debug - The process of going through the hardware or software and locating the errors that exist.
Delimiter - A character used to separate two or more items so you can tell where one ends and the next begins. Common examples of delimiters are the comma, the space, and the carriage return.
Differential Input - The input to an electronic device that outputs the difference in voltage between the two input leads. Noise common to both leads is cancelled by this arrangement.
DIP - An acronym for Dual In-line Package. This is the plastic case, wire leads, and silicon chip that make up an integrated circuit. A DIP switch is a plastic case containing one or more rocker switches that fit in the same type of socket as an integrated circuit.
Displayed Format Code (DFC) - A method of applying text formatting, such as underlining and italics, that is displayed on the screen as special characters.
DMA - Direct Memory Access. This is a technique that allows an I/O device to take control of the CPU and write or retrieve information directly to or from memory.
DOS - Disk Operating System. This is a program that handles all the work required to send and receive information from a disk. DOS will typically contain utilities that allow you to rename a file, delete a file, get a directory of your files, etc. Common examples of DOS's are MS-DOS (for the IBM and compatibles), TRSDOS (for the Radio Shack line of 8-bit computers), and Apple DOS.
Dot Matrix Printer - A printer that forms characters from a series of dots created by striking a set of vertically arranged pins in the print head.
Double-ended Input - This is the same thing as a differential input.
Drive Spec - The drive spec(ification) is the part of a file name that indicates the drive on which the file is located. The drive spec is separated from the rest of the file name by a colon.
DTE - Data Terminal Equipment.
Dumb Terminal - A device that is capable only of sending and receiving data. It has no way of storing data or any other advanced functions.
Dump - Writing the contents of memory to some output device such as a printer or disk file.
Duplex - This can be either half or full. Half duplex is a communications protocol for sending and receiving data but not simultaneously. Full duplex allows simultaneous exchange of data between two terminals.
Dynamic Link - A method of linking different files such that a change in the contents of one file will automatically update the contents of other related files.
EBCDIC - Extended Binary Coded Decimal Interchange Code. This is an 8 bit code used primarily by IBM mini and mainframe computers in place of ASCII. EBCDIC and ASCII can be interchanged if a converter program is used.
Echo - The process of sending back to the originating computer all characters as they are received. This allows the sending computer to determine if any transmission errors occurred.
EISA - Extended Industry Standard Architecture. This is a bus bus design that expands the standard IBM-AT 16-bit bus to 32-bit operation while remaining compatible with the earlier design.
EEPROM - Electrically Erasable Programmable Read Only Memory.
EGA - Enhanced Graphics Adapter. Maximum resolution is 640 X 350.
EPROM - Erasable Programmable Read Only Memory.
Execute - The process of performing the indicated operation.
Expansion Slot - A connector attached to the bus of a computer. Electronic components such as video adapters and serial interface cards plug directly into expansion slots.
Export - The ability of a program to create files in formats that are compatible with the programs of other vendors.
Extension - Up to three characters that are added to the end of a file name and are separated by a period from the file name. Extensions are usually used to identify classes of files. For example, Microsoft Excel assigns the extension XLS to spreadsheet files when they are saved to disk.
External Commands - DOS commands that are not in RAM at all times. These commands must be called from disk when they are needed. Examples of external commands are FORMAT, DISKCOPY, and DISKCOMP.
FAT - An acronym for File Allocation Table. This is the section of a disk that contains information about where files are located on the disk and how the space on the disk is organized.
Field - An individual entry in the record of a file.
File - Information saved on disk and assigned a name. A file could be a program or data created or saved by a program. In DBMS terminology, a file is a collection of records.
File Name - The name assigned to a file. Under MS-DOS, file names may be up to eight characters in length. A file name may contain an extension which can be three characters in length and is separated from the file name by a period.
Firmware - Software that is stored in ROM.
Flat-file Manager - A data management system that can work with the records in only one file at a time.
Floppy Disk - A secondary storage device using magnetic media coated on a flexible mylar disk.
Fortran - FORmula TRANslator. A high level language used primarily for scientific applications on large computers.
Format - The process of recording signals on a disk that indicate where sectors and tracks begin and end.
Framing Error - An error in data transmission which is the result of an improper start bit or stop bit.
Frequency Shift Keying - A method of transmitting digital data over telephone lines using alternating frequencies to represent 1's and 0's.
Full Duplex - A communications protocol that allows data to be sent and received at the same time.
Function Keys - The "F" keys on the IBM keyboard. These keys are used to perform special functions as defined by the particular software being used.
Gain Error - One of several types of nonlinearity errors associated with the analog to digital conversion process. Gain error represents an increasing deviation of the values output by the ADC from the actual input voltages.
GIGO - This is an acronym for Garbage In, Garbage Out. In other words, the information you get out of the computer is only as good as the data you put into it.
GPIB - General Purpose Interface Bus. This is another name for the HPIB or IEEE-488 bus.
Ground Loop Current - A source of noise in an electrical system that results from attaching each end of the shield on a shielded cable to devices that are at different electrical potentials. A shielded cable should have only one end of the shield grounded.
GUI - Graphical User Interface. Microsoft Windows and the Macintosh operating system are examples of a GUIs.
Half Duplex - A communications protocol that allows data to be sent and received but not at the same time.
Handshaking - The process of sending signals back and forth between two devices so that they stay synchronized.
Hard Boot - Starting a computer by turning on the power or restarting a computer by turning the power off and then on again. Some computers contain a reset button that performs a hard boot. This is also called a cold boot.
Hard Copy - a paper printed copy of information stored in the computer.
Hard Disk - A secondary storage device using magnetic media coated on a rigid metal platter. Hard disks are capable of storing large amounts (gigabytes) of data and can rapidly access the data.
Hardware - All the electronic and mechanical devices that constitute a computer system.
Head Crash - A situation that occurs when the head of a hard disk comes in contact with the disk surface. This usually results in the loss of data from the disk.
Hexadecimal - A base 16 number system. Two hexadecimal digits can be used to represent one byte.
High Level Language - Any programming language that uses easy to understand words to represent commands to the computer. Examples of HLL's include BASIC, Fortran, Pascal, JAVA, and C++. A single statement in a high level language may represent several instructions to the computer.
High Pass Filter - Any device or mechanism that allows high frequencies to pass through while filtering out low frequencies.
HPIB - Hewlett-Packard Interface Bus. This is another name for the GPIB or IEEE-488 bus.
IC - Integrated Circuit. An electronic device that packs many components onto a single silicon chip.
IEEE-488 - An industry standard parallel interface for connecting laboratory instruments to each other and to computers. It is also called the HPIB and GPIB bus.
Impact Printer - A printer that operates by striking a character generating device (pin or lever) against the ribbon and paper in the printer.
Import - The ability of a program to read the files created by programs from other vendors.
Index - A data file that is sorted on a particular field and contains pointers to the same records in the original data file. Indexing speeds up the process of finding records when the search is based on the field used to create the index.
Input Device - Any device which is designed to enter data into a computer. Input devices include keyboards, disk drives, light pens, etc.
Integrated Circuit - An electronic device that contains a variety of components (transistors, resistors, etc.) on a single silicon wafer.
ISA - Industry Standard Architecture. The 16-bit bus design used in the IBM-AT microcomputer.
Internal Commands - DOS commands that are loaded with the command processor and are always in RAM. Examples of internal commands are COPY, REN, and DEL.
Interpreter - A program that converts a high level language into machine instructions. An interpreter converts and then executes each line as it comes to it.
I/O Handler - The portion of DOS that controls all I/O. The I/O handler consists of two hidden files on the system disk called MSDOS.SYS and IO.SYS.
K - An abbreviation for the prefix kilo which means 1000 of something. In computer terminology, kilo actually stands for 1024, the closest you can get to 1000 by raising two to a power (210). For example, 64K actually means 65536 bytes of storage (64 X 1024).
LAN - Local Area Network. A collection of microcomputers and peripherals connected together in such a way that data can be shared among the devices.
LIMS - Laboratory Information Management System. A computer with associated hardware and software designed to automate sample logging, sample tracking, and report writing for chemical analysis laboratories.
Lock-in Amplifier - An instrument used to preserve a signal while filtering noise. The original signal is modulated at a fixed frequency. The detector is tuned to lock-in on the modulation frequency and receive the signal. Since any noise present in the signal path is not modulated, it cannot be detected.
Low Level Languages - Computer languages that use instructions that directly manipulate data in the CPU. Low level languages are more difficult to program but produce code that executes faster than that of high level languages.
Low Pass Filter - Any device or mechanism that allows low frequencies to pass through while filtering out high frequencies.
LSB - Least Significant Bit. The bit with the lowest place value in a binary number.
Machine Language - This is the lowest level language in which a computer can be programmed. Machine language requires no additional conversion before the computer can use it.
Macro - A collection of keystrokes or commands that is executed by one or two simple keystrokes.
MCA - Micro-Channel Architecture. A bus design introduced with the IBM PS/2 line of microcomputers.
Mnemonic - A memory aid. Assembly language instructions are also referred to as mnemonics because they are easier to remember than the corresponding machine language instructions. Load register A might be abbreviated as LDA.
Modem - MOdulator/DEModulator - This is a device that converts the signals sent from a computer into audio tones that can then be sent over phone lines. Both the sending and receiving computer must be equipped with a modem.
Monitor - The video display device of a computer.
Monochrome - Two color video display.
Motherboard - The main circuit board of a microcomputer. This board usually contains the CPU, most of the RAM, the ROM, the power supply, the video controller, and the expansion slots.
MSB - Most Significant Bit. The bit with the highest place value in a binary number.
Nibble - A group of four bits (or half a byte). A nibble can be represented by a single hexadecimal character. This is sometimes spelled nybble.
Noise - The undesirable components of a signal.
Nonlinearity - Any deviation from the ideal straight line relationship that should exist between the voltage input to an ADC and the value output by the converter.
Numeric Keypad - The group of keys on the right side of the keyboard that contains keys for numbers, arithmetic operators, and cursor control.
Nyquist Theorem - The sampling frequency of an ADC must be at least twice the signal frequency to avoid excessively distorting the signal.
Object Code - The machine level code produced from a compiler or assembler. Object code can be immediately executed since it is machine language. See source code.
Offset Error - One of several types of nonlinearity errors associated with the analog to digital conversion process. Offset error occurs when the output of the ADC always differs by a fixed amount from the actual input voltage.
Op Amp - Operational Amplifier. An electronic component that is used to build amplifiers, integrators, and comparators.
Output Device - Any device that is designed to accept data from the computer. Output devices include video monitors, printers, and disk drives.
Overrun Error - An error caused by the receiving UART getting data faster than it can process it.
Parallel Transmission - This is a transmission mode in which two or more bits (typically a byte) are sent simultaneously over parallel connecting wires.
Parity Bit - A bit that can be added to each data word to make the sum of the 1 bits either even or odd. This is used for error checking.
Pick Up Noise - Noise that is added to a signal due to the signal leads acting as an antenna and picking up stray electrical signals from the environment.
Primary Memory - This usually refers to electronic memory such as RAM or ROM.
PROM - Programmable Read Only Memory.
Quantizing Error - This is the minimum uncertainty contributed to the conversion of an analog voltage to a digital signal by the ADC. It represents the maximum resolution of the ADC and is usually +½ lsb.
Query - The process of extracting information from a database.
QWERTY - The name given to keyboards that have a standard typewriter layout. The first six letters of the second row spell QWERTY.
RAM - Random Access Memory. This type of memory is volatile and is used for "scratch pad" space by the computer.
Random Access File - A data file in which the individual records that comprise the data can be accessed in any order.
Read-Write Slot - The oblong opening in a floppy disk through which the read-write head accesses the disk.
Record - The smallest unit of a random access file that can be read from or written to disk. A group of related fields in a database.
Relational Database Manager - A data management system that can work with the records in more than one file provided the files have at least one common field.
RGB Monitor - A high resolution color (Red-Green-Blue) monitor. An RGB monitor cannot be used with a composite video interface.
ROM - Read Only Memory - This is nonvolatile memory. It comes preprogrammed with the computer.
RS-232c - This is an industry standard serial interface.
Savitzky-Golay Smoothing - A mathematical smoothing technique for noisy data that uses a polynomial based on the values of a specified number of data points that surround a given point.
Secondary Memory - This refers to data storage devices such as floppy disks, hard disks, and tape.
Sector - The parts into which a track is divided. IBM microcomputers (and their compatibles) divide each track on a 3.5" floppy disk into eighteen sectors. Each sector holds 512 bytes of data.
Serial Transmission - The process of sending information one bit at a time. This is the simplest form of data transmission and is typically performed using the RS-232c standard.
Sequential Access File - A data storage method in which the entire file must be loaded from disk into memory in order to access a single piece of information from the file.
Shielded Cable - A type of cable that consists of an insulated inner conductor (or set of conductors) surrounded by a metallic foil or wire braid. The outer foil (or braid) serves to shield the conducting wire(s) from stray electrical noise.
Signal Averaging - A noise reduction method that operates by summing a large number of repeated measurements. Any random noise present in the measurements will cancel out. The signal will not cancel.
Signal-to-noise Ratio - The ratio of the value of the experimental signal to the average amount of noise present in the signal. This ratio is used to indicate how much the signal exceeds the noise level and is an indication of how "clean" the signal is. This is usually abbreviated S/N.
Soft Boot - Restarting the computer by pressing the <CTRL><ALT><DEL> sequence. This clears all programs from RAM but does not execute all of the hardware testing that accompanies a hard boot. This is also called a warm boot.
Software - The programs that control the operation of a computer. A computer is unable to perform any function without some sort of software to direct it.
Source Code - The code produced by a programming language prior to assembly or compilation. Source code cannot be executed. See object code.
Spreadsheet - A method for organizing and manipulating numbers by rows and columns.
Start bit - A bit that is added at the beginning of each data word during serial transmission to indicate that data are coming.
Stop bit - A bit (or bits) that is added at the end of a data word during serial transmission to indicate the end of that particular data word.
System Clock - The crystal controlled clock that synchronizes all of the signals moving through the computer.
Text File - This is the same as an ASCII file. The file contains only text with no control codes.
Track - Concentric circles of data storage on a disk. IBM microcomputers divide each surface of a floppy disk into 80 tracks (numbered 0 - 79). Corresponding tracks on opposite sides of a disk are referred to as a cylinder. Each track of a floppy disk is divided into eighteen sectors. Each sector holds 512 bytes of data. Total storage on a 3.5 " floppy disk is determined by the following: 80 tracks/side X 18 sectors/track X 512 bytes/sector X 2 sides = 1,474,560 bytes.
Transducer - A device that converts a physical/chemical phenomena to an electrical signal.
TTL Monitor - A high resolution monochrome monitor. (TTL stands for transistor-to-transistor logic.) A TTL monitor cannot be used with a composite monitor interface.
Twisted Pair - A type of signal wiring that consists of two wires twisted around each other along their length. Twisted pair wiring rejects noise better than parallel wiring.
UART - Universal Asynchronous Receiver Transmitter - The device used to convert parallel data from the computer into serial data during serial transmission. A UART is part of any RS-232c interface. The UART also converts serial data back into parallel data at the receiving end.
VGA - Video Graphics Adapter. Maximum resolution is 640 X 480. Super VGA, or SVGA, has a resoluton of 800 X 600. The Extended Graphics Adapter, or XGA, has a resolution of 1024 X 768.
Video Display Adapter - A circuit board that plugs into an expansion slot and allows the computer to interface with the video monitor.
Virtual Memory - A memory management technique where data appears to be in RAM when it is actually located on a secondary storage device. Data is shuffled back and forth between primary and secondary memory.
Wild Card - A character that takes the place of one or more characters in a file name or instruction. In MS-DOS, the questions mark can be used to replace any single character and the asterisk will replace multiple characters. For example, the command COPY DAT*.* B: will copy all files beginning with the three letters "DAT" and having any extension from the current drive to drive B.
Word - The number of bits that the CPU can work with during any single arithmetic or logic process. The greater the word length, the more powerful the computer.
Word Wrap - A feature of word processors that will place a whole word on a new line if it does not fit on the preceding line.
Write-Protect Tab - A sliding plastic tab that is placed over the write-protect notch on a floppy disk. When the notch is covered, data can be written to the disk. When the notch is open, the disk is said to be write-protected.
WYSIWYG - What You See Is What You Get (pronounced wizeewig). This name applies to a class of applications software which shows you on the screen exactly what will appear on the printed copy.
XON/XOFF - A handshaking protocol used with serial transmission devices.