CPU — Central Processing Unit
The supposed brain of a computer. It is the CPU that carries out instructions (from a program), in order to perform tasks. Each instruction takes so many cycles to be performed. The chip oscillates in accordance with the megahertz (or chip speed). A 133 MHz chip produces 133,000 cycles per second. The more cycles per second, the more instructions can be carried out in that time, hence the faster the machine.
Bus — 16-bit or 32-bit
The bus is a series of "wires" that carry data and commands around the computer. The CPU, memory and expansion card slots are all located on the bus. Each wire is capable of carrying a high (ON) or low (OFF) binary digit. Therefore, a 16-bit bus is capable of transmitting two bytes (1byte = 8 bits) at any one time. Consequently, a 32-bit bus can carry four bytes at a time. The wider the bus, the more data can be carried, greatly aiding machine performance.
IRQ — Interrupt ReQuest
Every piece of hardware — such as the mouse, modem, printer, graphics driver — needs to know when a command issued is for a particular device. For example, when the computer wants to print something, a command is sent to the printer. How does the printer know the command is for itself? The answer is the IRQ.
Every device has a unique IRQ number (ranging from 1 to 16). When instructions are designed for a particular device, the IRQ line is used. This goes two ways. Not only can the CPU send commands to a device (such as a printer), but also devices can send the CPU commands too (such as the mouse).
IRQ instructions are constantly scanned and are intermingled with general processing. This gives the computer the chance for an instant response when many things are happening at once. For example, the computer may be printing a document while the mouse is moving and the screen is being updated.
It is essential that devices do not try to share the same IRQ number. If this happens, a hardware error occurs as two devices are trying to process the same command. This is generally known as a "hardware conflict." Most devices can have their IRQ's changed, but not all.
BIOS — Basic Input / Output System
The BIOS is mainly concerned with the ability of a computer to fetch and store data. To this end, it is primarily concerned with disks. This is an extremely important function, particularly for a machine like the PC whose operating system lives on disk rather than specialised ROM's.
