Computer Mission Impossible

By Cormac Betts


Everything inside the computer is connected to a circuit board called the 'motherboard'. The motherboard has sockets for low-level programming (BIOS), the computer's brain, called a CPU; the computer's memory (RAM, ROM and CMOS); and for add-on cards to control the video (picture), audio (sound), printer and anything else that might be connected to the computer. You may also find a modem inside on an add-on card.


stands for 'Central Processing Unit' and is the 'brain' of the computer. Most CPU's today are made by Intel and bear such names as 'Pentium', 'Pentium Pro' and 'Pentium II'. Older Intel CPU's include the 80486 and 80386 families. Other manufacturers also make CPU's: Motorola for the Macintosh, AMD and Cirrus for PC's and others. The 'speed' of a CPU's processing is measured in megahertz. The CPU is the place that holds info about the operating system (DOS or Windows, for example


RAM is what you know as “Memory”, as in how much memory does your computer have? It is not permanent memory - the RAM is erased when the computer turns off. Permanent memory is stored on the hard drive. Memory is measured in increments of bits and bytes. Generally the least memory you should ever have with a Pentium computer is 64 MB (megabytes: look up kilo-, mega-, and giga- for more info), and more is much better. There are places on the motherboard (called “slots”) for memory modules. The memory modules are small printed circuit boards with memory chips on them and are usually either SIMM’s (Single Inline Memory Modules) or DIMM’s (Dual Inline Memory Module).

Don't confuse this with RO

expansion board

This is an add-in or expansion board such as a video card, sound card or modem. On every motherboard there are places to add circuit boards to extend the capabilities of the computer. The most common circuit boards used are the internal modem, sound card, and the video display adapter. There are various types of expansion slots that may be on the motherboard. The ISA (Industry Standards Association) expansion slot is the older type and most of the older circuit boards used this type of slot.

hard drive

The hard drive uses disks that are made of aluminum or glass (and therefore 'hard'). Each disk can store much more information than either a floppy or CD-ROM. Sometimes, there may be several disks in a hard drive. However, the disks in a normal hard drive can not be removed or replaced. Today, hard drives are measured in gigabytes. That's one thousand million bytes. 1 gigabyte is about 11/3 CD-ROM disks. Sometimes a special cache is used for quick retrieval of often-used information (such as web pages). This is just a separate directory on the hard drive..


A modem allows your computer to connect to another computer using the normal telephone line. It converts data from a computer format, which requires many wires, into a format that can be sent using only the two wires of a telephone line. At the other end of the telephone wires the process is reversed. Data transfer rates from the modem vary from 14.4Kbs to 56Kbs. (14.4Kbs, 28.8Kbs, 33.6Kbs, 56Kbs) There are special types of modems such as cable modems that can communicate at much higher data rates.


At one time there was the PC keyboard, the AT keyboard, and the 101 key enhanced keyboard, which had F9 through F12 keys and a separate numeric keypad. Now the 101 key enhanced keyboard is the standard type and keyboards are named according to the type of connection it makes to the computer. The two common types of connectors that go from the keyboard to the computer motherboard are the AT and the PS/2. The AT is the larger older type, and the PS/2 is a newer type and communicates better with he computer.


CD-ROM stands for Compact Disk – Read Only Memory. The original name was WORM drive, which meant Write Once Read Many. So the term CD-ROM is not really very accurate, but it is the name that has stuck.