ABC of Computers Major Definitions
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ABC of Computers Major Definitions

Computer Parts of a computer RAM CPU
Account ASCII
Backups Bits, Bytes, Binary and Digital Buffer
Computer Aids Computer Centres
Default DOS Electronic sources
Files Computer file filenames File Managers
Fonts Format Formatting floppy disks
gremlins, bugs, crashes and illegal operations
Information Data Networks
Password PINnumber
Programs Software
Systems Software Operating Systems Application
Terminals Text file Tools Username
Windows Wordprocessor Text Editor

Computer History: Alan Turing's computable numbers 1935 - hardware and software 1947 - computerising production engineers in 1963 - monster computers in the 1960s - cold war communications in 1969 - Computing 1981 - Computing 1989 - world wide web 1993


Computers started as counting and calculating machines (computers).

Modern computers are very powerful electronic counting and calculating machines that can also convert words into numbers, rearrange them, and convert them back into words (word processing). By similar conversions they can also draw pictures, play music, make a telephone call or control your washing machine. Computers have always processed information. The early computers could only process it in limited ways. Modern computers, however, can also store information in vast quantities, and this information includes stored programs that manipulate data in different ways. What a modern computer does depends, therefore, on the program or software that it is using.

On their own web page:

Keyboard and Mouse Commands

Internet Words

Moving Text

Storing Text


Software listing

Beginners' Guides

The small computers that we use personally are called Personal Computers (PCs).

The usual parts are:

The solid parts of a computer are called Hardware. Click here for the illustrated hardware page.


If you want to keep money in a bank, or borrow from it, you have to open an account with the bank. When many different people use the same computers, each can have an area of the computer's storage memory allocated to his or her use. This is also called your account. To get into your account you usually need a username and a password. Entering your account is called logging in. Leaving your account is called logging off

Apple Macintosh:

A major computer manufacturer whose computers work on different principles from the IBM compatible computers that most people use. Macs or Apple Macs are often used by people who work a lot with pictures. The people who write North Circular, for example, use them. A lot of work has been done to enable Apple Mac and IBM compatible computers to exchange information easily, but there are still problems.

ASCII (Pronounced "ass-key") is an acronym from American Standard Code for Information Interchange. ASCII is a universal computer code for converting the basic English letters and other characters into the binary numbers that computers use. Using this basic set allows information to be moved from application to application and from computer to computer with great ease. See plain text; text file and file conversion.


Backups are copies of computer files made and kept as a safeguard in case of damage or loss of the originals. There are different types of backup. These include Timed and Original backups.

Bits, Bytes, Binary and Digital

These terms all relate to the fact that computers think in twos. Their thinking is all done in combinations of two electrical positions, similar to a light being either on or off.

A bit, or binary digit, is the smallest amount of information a computer handles. Each bit can be on or off representing 1 and 0.

A string of eight bits is a byte. The number of ways eight bits in a line can be on or off is 256. A byte, therefore, has 256 possible patterns. Each of these patterns is used to represent one character, like a, A, b, B, 1, 2, etc.

Binary means doing things with twos. If music has two beats to a bar, it is in binary measure. Two stars that revolve round each other are called a binary star. Binary digits are groups of two numbers (usually 0 and 1, as above) used to count the way that computers do.

Click for more about binary arithmetic

A Digital Computer does all its basic thinking in (binary) numbers. It is a digital device that performs its tasks by turning on or off a series of electronic switches. (a switch turned off representing a binary 0, a switch that is on representing a binary 1). Signals in separate bits, like this, are called digital signals. All modern computers use them, but earlier computers used continuously varying devices like turning wheels or an electronic current smoothly varying its frequency and strength. Smooth signals like this are called analogue signals.

The telephone system is an analog device and so an electrical converter (called a modem) has to be used to translate the signals a computer uses into signals that can travel along the telephone wires.

Because computers think digitally, the adjective digital is used to mean that something is related to computers. For digital technology means the technology of computers.


A working computer keeps some data ready for immediate access. Some of this it is currently working on. Buffers keep information that is waiting to be processed.

The Windows Clipboard is a buffer where data that has been cut or copied from an application is kept incase you want to recall it. The clipboard only keeps the material you last cut or copied. Each time you cut or copy something the previous contents of the clipboard are deleted.

Most applications have similar buffers that keep data you have deleted, incase you want to undo your deletion. WordPerfect 5.1 has a buffer that keeps the previous three items that users delete.

Computer Aids:

Computer Aids are the programs and tools that go with:

Computer Assisted Learning (CAL);
Computer Based Learning (CBL): and
Computer-aided Writing.

The tools include spell-checkers, grammar-checkers and thesauruses. In Windows Applications they are usually available on the tools menu.

Examples of computer based learning programs are Helpdisk!, which is about essay writing and English Language: an introduction to basics.

Computer Centres:

The term Computer Centre is rather general. It could be a shop for selling computers. On the other hand, it could be a computer resource centre, or part of a resource centre, that specialises in resources for using and learning to use computers. As such it will have computers for people to use and professionals to help them use them. Each campus of Middlesex University has a Computer Centre like this.

Computer resource centres may become more common as the Government's IT for All programme takes effect. The computer resource centre for Hackney residents, however, opened in 1999 and closed later the same year!


In every-day English, to default is to fail in one's obligations. In computing it does not have a moral meaning.

The default settings of a computer program are the options it selects if you do not instruct it to do otherwise.

For example, if you just start a wordprocessor it will probably provide A4 size pages with one inch margins.

If you give a computer instructions that it cannot follow, it may default to another instruction.

For example, if you type in a web address that does not exist, the browser may default (go) to a web page that tells you it does not exist and advises you how to look for the page you want. Sometimes it will default to the home page of the site.


DOS stands for Disk Operating System. That is a program without which your disk will not operate. The operating system is automatically loaded into a computer when it is switched on.
It is also used:

    1) As an abbreviation for MS-DOS, a disk operating system sold by Microsoft .

    In this sense, it is contrasted with Windows (which is also sold by Microsoft).

    When you switch on a computer with a Microsoft DOS older than Windows 95, you usually get a black screen with a c:\>_ (or a:\>_) prompt at the side of the screen.

    Commands (code words like wp or win or copy) typed in at the prompt are acted on when ENTER is pressed.

    Some of these commands will start other programs if they can be found on the disk. The command win, for example, will probably start Windows 3.1

    Versions of Windows from Windows95 go straight to a Windows screen when the computer is switched on. A computer can easily be told to do the same with Windows 3.1.

    2) To refer to applications designed to run on MS-DOS as distinct from Windows.

    WP5.1 (Wordperfect for Dos version 5.1) is an example.

    DOS applications can always be run from the DOS prompt.

    In most cases they can also be run in Windows. If WP5.1 is run in Windows, one can switch backwards and forwards between WP5.1 and other applications (like an internet browser or an email mailer) in the same way as between Windows applications.

    Applications designed to be run under Windows can not be run from the DOS prompt.

Electronic sources and electronic communication:

These include wireless and television, telephone, computer files, CD-ROM, video and film, and the internet.

Internet resources


A computer file: is a collection of electronic information stored under one name. Computer programs are stored in files, but the computer files that students use store data.

Compare this to paper files

file names:
(Based on Johnson, R. 1996/electronic pp 20-21):

Filenames on computers are much more important than labels on paper files. As well as being a label for the contents of the file, they are part of the system that records its location on the

The more clearly and systematically you name files, the easier it will be to find documents.

There are differences in the way operating systems and wordprocessors name a file. Some wordprocessors (the Apple-Mac) and some operating systems (Windows 95) allow you to give full titles as filenames. You could call the name of a document wordprocessing or essay-on- Freud.

On most other personal computers, however, the filename can only have up to eight characters, plus an optional full stop and a three-letter extension.

In general form this is shown as *.*, where the asterisk before the dot indicates any name up to eight characters; the asterisk after the dot, an extension of up to three characters.

This might let you call the files wordproc.ess or essay.fre. However, Windows Applications tend to use the extension to indicate what the file format is. A file called:

*.TXT being a text file
*.WRI a Write file,
*.DOC a Word for Windows file,
*.WPD a Wordperfect for Windows file etc.

The art of file naming, therefore, is really to find eight letter titles that are as descriptive of the file's contents as possible.

File managers:

File managers on computers allow you to organise your files and directories. You can look at the way files are organised on a disk, move and copy files, search them, look inside a file, delete files, create directories, travel around a directory tree and do a multitude of other things. The WordPerfect 5.1 file manager is called List because it lists the files in a directory.

The file manager on MS Windows versions since Windows95 is called My Computer.

When you open it, it looks something like this:



The word font comes from the printing trade. It has changed its meaning slightly in moving from the description of metallic typeface to electronic letters. Fonts give shapes and sizes to the basic characters that are used in wordprocessing. ASCII text does not have any font. The usual font for essays is the typeface Times in size point 12.


The word format comes from Latin for shape. In English it was traditionally used for the style and shape of books. Computing has used it for at least three different things:

1) Formatting text: Nearest to the traditional use is when we use it to mean shaping text. The format of the text refers to everything that we add to the basic letters: the margins of the page, the line spacing, page length, size of letters, type of letter ( font) etc.

2) File formats: The format of the text produced by a wordprocessor is something that we can see. The computer file also has a hidden format (shape) that is different with every make of wordprocessor. The file format of a Wordperfect 5.1. file is different from a Word for Windows file, for example. For any wordprocessor to read files created by a different type of wordprocessor, the file format has to be converted.

3) Formatting disks: The magnetic particles on a computer disk have to be shaped before the disk can store information. This shaping is also called formatting.

Formatting floppy disks:

If the floppy disks you buy are not pre-formatted, you can do it yourself from the DOS prompt, or in Windows File Manager.


Information in computers includes programs and data

gremlins, bugs, crashes and illegal operations

Gremlins are mythical little people, evil spirits, mischievous devils, which cause sudden and unexplained faults in machines.

Gremlins were invented by the United Kingdom Air Force (Royal Air Force) during world war two to explain some of the things that happened to their planes.

Computer gremlins, sudden crashes, systems that stop working, faults that continually reappear (etc), have definite causes, but the computer user does not know what they are, or cannot solve them.

In the United States, computer experts suggested that mysterious failures of machines might be due to an insect (bug in American) getting into the computer. If you find the insect and remove it, the computer would work again. Of course, it is usually the computer program that has one or more faults. Finding and removing faults in computer programs is, therefore called de-bugging

A crash is when a computer program or the computer stops working suddenly. You may get a message that the program has performed an illegal operation, and will be closed down.

If a computer programmer creates a gremlin/bug and puts it on other people's computers, it is called a virus.

Although erring is human, and fouling things up completely uses computers, psychological survival requires forgiving yourself, humanity, and computers. Kicking is a bad idea.

log in   log on

These terms were invented in the 1960s and 1970s by people who made computer systems. They mean providing the details you need to enter your own account on a shared computer or computerised system. Usually these are a user name and a password

log out   log off

This means leaving your account space - but doing so in such a way that it cannot be entered without the username and password (or whatever).


Computer networks are made by linking computers by cables and wires over which they communicate electronically.

Millions of computers around the world are linked in different networks through fibre optic cables, phone lines and satellites. With a modem any computer can link into large parts of these networks. Middlesex University [1999] has Local Area Networks (LANs) on each campus, which are linked together in a Wide Area Network (WAN). This Middlesex University WAN is linked by the internet to networks throughout the world.

PIN number

A password is a word you have to give before you are allowed to pass. Accounts and sometimes files on computers are protected by passwords in order to keep out people who have no business with them, but they just as often keep out people who have. You need to think carefully about how you are going to remember your passwords.

Usually you have to remember two things: A userid (User ID, User Identification) and a password.

Sometimes you need more.

PIN number:
Personal Identification Number People with cash machine cards have secret pin numbers they type in to identify themselves. People
with accounts on computers use username and password to do the same. The computer catalogues in Middlesex University libraries ask you for a PIN number if you want to order a book. Fortunately you can just type in 111111. (As long as you do not alter it to make your PIN number a personal secret).


A program (or software) is a sequence of instructions, in computer language, that tells the computer what to do. One program can be replaced by another, so the computer becomes a machine for doing whatever it can successfully be told to do by a program.

The program you are using at the moment is probably an internet browser like Netscape.
Many people are busy writing new programs to get computers to do new things.

Programs are stored on your disk as computer files with the extensions .EXE or .COM


Software is a general term for all programs that can be used on a computer. There is little difference between "software" and "program", but software may include associated documentation.

An application is software that performs a function directly for a user, like a wordprocessor or browser.

Systems software includes programs that control the way the computer operates, like DOS and Windows. These are called operating systems.

Software listed


Take care of yourself. You are precious. In a different way, so is your work. Ways of taking care of this include, keeping copies of work that you hand in for assessment; taking backups of work that you are doing on a computer; and knowing the escape or cancel key when working in a computer program.


Computer terminals are usually screens connected to large computers elsewhere.

Text file:

Text files are the simplest form in which documents can be stored on a computer. They are also called ASCII files and Dos Text files. Text files have just the basic printable characters (a, b, c, etc) with just a few codes that can format or shape the text. These codes control things like tabs, page breaks and the divisions between lines. Text files do not include more complex formatting like bold, underlining, italics and fonts. Files with this, more complex, formatting are called binary-files. Computer programs that edit text files are called text editors. Computer programs that edit binary document files are called word processors. Word processors can import text files. They can also convert their documents to text files. In converting to text files formatting like bold, underlining, italics and fonts is lost. Because text files are the simplest form of computer document they are useful for moving words between different programs. A document can be exported from a word processor, imported into an email program, sent across the internet as an email, exported as a text file and imported into a different word processor.

Plain text in a computer file is not a text file unless it is saved as a text file. If it is saved in the format a wordprocessor uses it will not be a text file because it will contain extra characters used by the wordprocessor.


Tools or utilities are programs on computers that enable you to perform a specific task or small group of tasks. The tool may be part of a larger application, or it may be a separate program. See computer aids.

Userid or User ID or User Name

ID is an abbreviated form of saying identification or identity.

Your userID or username is the code by which you identify yourself to a machine or a computer system. See

Different meanings of "windows":

Windows are rectangular areas on the screen in which you can view an application or document.

Using windows as a sceen display system is a way of having different applications, parts of them, or documents, displayed on the screen at the same time.
This is a simple example of a window. Normally you cannot write on a web page, but the window on the right allows you to do so.

Windows, in this sense, are used by DOS applications as well as by those normally called Windows. For example, in the DOS wordprocessor WordPerfect 5.1, you can split the screen into two editing windows, each with a different document.

Apple Macintosh, and then Microsoft Windows, used this windows idea as part of a graphical screen which users intuitively respond to by clicking on icons with a mouse. The browser you are reading this in is almost certainly running on such a windows system. It may be running full screen (taking up the whole screen), but it can be diplayed as a window that only occupies part of the screen.

On such a windows system, you can split the screen into several windows, each with its own frame. Each window can be moved, opened, closed and resized without affecting the others. There is normally a small button in the top right corner of the screen or window that allows you to switch between windows display and full screen dispay.

To switch between windows you move the mouse pointer to the window you want to work with, click on it once and it becomes active. You can often reduce a window to an icon or enlarge it to fill the whole screen. Sometimes windows are displayed within other windows.


Windows Windows (with a capital W) is a Microsoft trademark for its operating system which uses windows.

  • Windows 3.1 ran on top of the DOS operating system.

  • From the user's point of view, Windows 95 and later versions run as if they are the only operating system. This means you just start with a user friendly screen layout)

Windows Applications:

A Windows application is software that is designed to run in Microsoft's Windows and does not run without Windows (see DOS).

Large numbers of Windows applications are made by firms other than Microsoft. Well known examples include the wordprocessor Wordperfect for Windows,   the browser Netscape,   the graphics converter Graphic Workshop   and the mailer Pegasus

All Windows applications have common features to their screen layout and use common commands by mouse or keyboard


Wordprocessing is electronically writing, editing, and storing what you write. To do this, you use a Wordprocessor or Text Editor.

Wordprocessors and Text Editors

A "wordprocessor" can mean two different things:

    It can mean:

  • A small computer which is used as a typewriter to produce letters and other documents. An example is the Sharp wordprocessor.

    But, the most usual meaning is:

  • Computer software that allows you to write, edit and print letters and other documents. Examples are Microsoft Word and WordPerfect

A Text Editor works in ASCII text. It is much smaller than a wordprocessor as it does not include any formatting, or the extras like graphics that modern wordprocessors provide. Examples are Windows Notepad and TextPad

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