Computer Terminology


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Computer Terms Tutorial Overview

Topics covered in this tutorial (click link to jump to topic):

1. CPU 8. Hard Disk Drive
2. BIT, BYTES and BINARY 9. Floppy Disk
3. Hardware 10. Input Devices
4. Software 11. Output Devices
5. Operating System 12. Types of Computers
6. ROM 13. Booting
7. RAM    



CPU stands for central processing unit. This is where all the computer's data processing is handled - all the data manipulation, calculations and formatting data for output. When you buy a computer you will become more focused on the CPU and its capabilities.

The execution of the instructions within the computer system is extremely fast and is measured in cycles of time and referred to as megahertz. For this reason the Mhz of a computer’s processor is sometimes referred to as it’s clock speed. Think of CPUs (and aligned circuitry) pulsing like a heart, this pulsing is expressed as "MHz" e.g. 2400Mhz.

The CPU pulsing is turning electrical current on and off. An electrical circuit can be either open or closed, and the power is either running through or not; that is, it is either on or off. This two-state situation is called binary, and the two states are controlled by binary digits or bits. The two bits of a computer are zero and one. For you to talk to your computer your message must be translated into binary form, a series of ones and zeros.

The CPU is located usually around the centre of the motherboard, and under a giant fan employed to keep it cool. The motherboard is the main piece of circuitry of your computer. It houses the CPU, the ROM and RAM, a variety of computer cards for receiving signals from other input devices, the power supply, hard drive and so on.

When buying computer you may choose between AMD processors and Intel processors. AMD and Intel a computer chip manufacturers. They have ben vying for market share for some years now. Each manufacturer has different ranges of processors aimed at different markets and applications. E.g. AMD's Semperon and Intel Celebrant were both entry level processors shipped in budget systems. Generally speaking the greater the speed of a computer the more expensive it will be.

The term CPU is sometimes used to refer to the case that houses the computers components, but technically the CPU is only one chip inside the computers case. The case is sometimes described as the "tower" which means the case stands on the floor on its narrow side. Whereas a "desktop" machine sits on your desk and generally has the monitor placed on it.

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RAM means "ready access memory" (or sometimes "ready access memory"). It is like a temporary notepad where your computer sends information it has processed before writing it to disk, or where instructions from other input devices (keyboard, mouse floppy drive) are stored. The words "random access" indicate that memory locations in RAM are accessible in any order unlike sequential access of a data cassette tape, for example.

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Hard Disk Drive

Your computers hard disk drive is like an audio CD that you have at home - accept the your computer can read and write to it. On other words, your computer can take data off your hard drive (to process it in the CPU or place it in RAM to work with) or it can record the results of the work it does back to the disk, this is called "writing to disk". The abbreviation HDD means "hard disk drive".

If you opened up your HDD (not recommended as this usually voids the manufacturer's warranty), you would find a pancake stack on double sided disks.

Each side of each disk had a arm that holds a "head". The head is responsible for writing data to the disk. When you handle a disk, carry a computer or laptop you should be careful to not bang the case as this can force the heads to collide with the surface of the disk and potentially damage it.

Hard disks are "formatted" to make them writable In this process "clusters", "sectors" and a "file allocation table" are created. With these mechanisms the computer writes information to the disk and can retrieve it later.

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Floppy Disk

You can also read and write data to a floppy disk. It is simply smaller than your HDD and portable - you can take it to another computer and read from it there. Floppy disks are sometimes known as "secondary storage devices". Today’s floppy disks are not floppy. They were called floppy originally because they used to be 5 inches in width and floppy. They could carry about 720kb of data. Today however floppy disks are smaller and rigid and can carry more data (1.44Mb).

New floppy drive options are appearing on the market. Zip disks by Iomega are high volume floppy system that allows you to store up to 250MB on a floppy-like cartridge.

Newer USB drives come in sizes up to 4GB and are much faster than either floppy or zip disks. They are smaller too, making them more portable (and prone to being lost). The write times to USB drives is very fast now making saving and backing up easier. The old floppies were also highly susceptible to damage and corruption. USB drives on the other hand are robust.

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A bit stands for Binary Digit. A byte is 8 bits. A kilobyte (kb) is 1,000 bytes. A megabyte (MB) is approximately 1,000,000 bytes. A gigabyte (GB) 1,000,000,000 bytes - that’s a lot of bits!!!

A bit is the smallest information parcel on your computer. A computer file can be made up of many hundreds of bytes and many thousand of bits. The bits are like switches, the are represented by 0’s and 1’s. Characters on your keyboard are therefore represented by 1’s and 0’s, so a "P" may be 01010000 to your computer - it knows when it sees those on/off instructions that you mean to output a "P".

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Hardware is the term given to all the physical parts of a computer system. Hardware includes the monitor, the keyboard, the mouse, the main case which houses the RAM, CPU and the motherboard.

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Software is the term used to describe the instructions needed to make the computer work. Software is not tangible; you can not touch it. Software is also called a "program" and is a set of computer files that are used to perform various actions on the computer. You may have a program for word processing, for example. Software can be transported on compact disk and floppy disks, but usually sit on the computers hard drive waiting to be "run".

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Operating System

Every computer needs a set of programs called the operating system to run the system and make all the other programs work. Your word processor, database or spreadsheet programs can not operate unless the operating system is present. Programs written for one operating system will not work on a different operating system.

Common operating systems include: Windows (current version is Vista), Linux (there are many versions aimed at different uses) and Macintosh OSX. Windows dominates

Windows Vista 18%
Windows XP 67 %
Windows 98 less than 1%
Windows 2000 1 %
Linux 4%
MacOS X 6%

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ROM means read only memory. Your computer’s ROM is a chip on the motherboard that stores a permanent set of start-up instructions for your computer. The familiar term for ROM is "BIOS", short for "basic input output system".

ROM is sometimes referred to as "firmware" (as opposed to software) because it is permanently housed inside the hardware. Instructions in ROM remain intact when the power is off.

Generally you can not alter the information in ROM; it is fixed at the time of manufacture. Some manufacturers provide updates to the ROM of their chips. The process of installing these updates is called "flashing the bios". This is only recommended for advanced users and only after all other avenues of repair are explored.

Your audio CDs at home are ROM, meaning you can only play them, or "read" them, but not record on them or "write" to them.

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Input Devices

An input device is anything used to give a command or information to your computer.

1. The Keyboard

The big flat thing you type on. The keys are arranged much like those of a type writer, except a computer keyboard has a row of "function" keys that provided extra instructions for the computer e.g. F3 instructs the computer to find.

2. The Mouse

The mouse is a pointing device. It is often operated in conjunction with the keyboard. The mouse appears as a small, white arrow on the screen. When you move the mouse around on the "mouse pad", the white arrow makes the same movement on screen. The mouse allows you the place the cursor on the screen, block text and to drag and drop files.

For gamers the mouse can be replayed by a joystick or a console.

3. Other

Other common input devices may be a microphone, a scanner, a tape drive or a video camera. For WindowsMobile, a plain plastic stylus acts as the mouse.

Things that are plugged into the computer are often called "peripherals". The word peripheral when related to computers means "outside" or "external". Peripheral devices are hardware devices that are outside the systems unit but can be attached to it so that they can communicate with the CPU.

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Output Devices

1. Printer

Prints a file to paper. A printer is likely to be a laser jet printer at work or an ink jet printer at home.

Ink jet printers thermally generate bubbles to eject streams of ink. The electrical current is generated by the printer’s microprocessor. This activates a tiny heating element in the ink nozzle. Intense heat causes the bubble to burst and spray ink onto the page. Provides cheap colour printing.

Laser printers beam a pattern of fine dots onto a rotating drum that is coated with light-sensing electrostatic material often called "toner". Electronically charged particles of toner are pressed onto the paper as it passes over the drum. The particles are then heated until they set. Laser printers are the most silent and produce very high quality printing.

2. Monitor

The Monitor or VDU ("visual display unit") provides a temporary way of outputting text or graphics. The visual display seen on the screen is actually a group of dots of light known as pixels (abbrev. from "picture elements"). The great the number of pixels, the greater the resolution of the image and the clearer and sharper the picture is.

3. Speakers

The speakers simply output sound. Speakers are plugged into a sound card attached to the motherboard. Sound cards vary in quality. Most modern sound cards provide stereo sound.

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A modem is used to receive and send computer files over telephone lines. Modem means "mo"dulate and "dem"odulate. A modem is device for converting the analogue signal of a telephone line to a digital signal so your computer can understand it. And doing the reverse, taking the digital signal of your computer and turning it into an analogue signal. A modem can be internal - a card plugged into your computers motherboard, or external, a separate box plugged into one of the COMS ports of your computer. A modem’s speed is measure in kilobytes per second, or kbps.


In the Windows environment the user encounters, pop-up or drop down menus. A menu is a list of functions you can choose. They provide the user with quick access to some of your software’s more frequently used functions.

Look for "…" after menu options; this means there is another menu or a "sub-menu" under this option. Likewise for the character "u". Options that appear in pale gray on a menu can not be accessed. It get access to them you may have to highlight some text or a picture file.

Also note that there is an underscore under a letter of a menu option. This indicates that you can push the <Ctrl> key and that letter concurrently to activate a function rather than selecting it off the menu with several mouse clicks.

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Types of Computers

1. Personal Computers

Personal computers or just the "PC" is a medium-sized, desktop computer. Today’s PCs are many, many times fastest and have much more storage capacity than their early forerunners. Today’s PC’s perform a huge range of functions that were barely conceived of only 10 years ago. Generally a PC is not connected to other computers or "networked" but it can easily be connected to a network with the edition of a network card and cables. A "Laptop" is a PC, but just smaller and therefore portable.

2. Personal Digital Assistants

Personal Digital or PDA is a small (they can be as small as pager or the size of a small paper back book) computing device with a cut-down operating system and cut-down applications. They are miniaturised computers with limited storage ability and no hard disk. All the files they need to operate, and the program files, are stored in RAM. Generally, today, they are "Internet ready" meaning that you can connect to the Internet with a PDA, send and receive mail and browse the World Wide Web.

3. Mainframe

A mainframe computer is a very large computer, sometimes taking up the space of a whole room. It can process very large amounts of data at very high speeds and is used by large companies and corporations and government departments. A mainframe may have many other computers or terminals attached to it so many people can use it at once.


The term "booting" refers to the start up of the computer and the loading of the required parts of the operating system into RAM.

When the computer is first switched on:

  1. The permanent instructions residing in ROM start up. They test the machine to see that all the physically parts are present and working. BIOS information will be displayed on screen at this time (look for the rectangular box enclosed in double white lines).
  2. The computer then carries out a quick test of the machine’s memory locations (see the RAM ticking over on screen).
  3. Then the system will head to the hard disk drive or the C: drive and will start to load the operating system.
  4. It finds the system files, io.sys, msdos.sys and loads them into RAM.
  5. If there are peripherals that windows does not recognise an autoexec.bat file will execute
  6. Windows then loads over the top of DOS (disk operating system)

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