Open Site - Computers: Hardware: Components

Top: Computers: Hardware: Components

[ history ]

Central Processing Unit

The Central Processing Unit is the brain of the computer. It is responsible for executing the machine code instruction set that controls the system. The CPU fetches these instructions from memory and these instructions control every aspect of the computer's operations.

Some of the tasks performed by these instructions are:
- Writing and reading data, to and from memory
- Writing and reading the ports in the system. These ports are used to interface with the peripheral devices contained in the system (e.g. - the keyboard, the serial and parallel ports, etc.)
- Controlling the arithmetic processing unit to execute mathematical operations

[ history ]

Memory

The memory sub-system is the work area the CPU uses for reading instructions to execute, and for the reading and writing of data. Memory is frequently referred to as RAM or Random Access Memory. This is because any memory location can be accessed directly through it's address, rather than having to read sequentially through every location to get to a desired address. Another commonly used acronym is ROM which refers to Read-Only Memory.

The information kept in memory is typically temporary; it disappears when the system is shut off or rebooted. However there are some forms of memory where the information is persistent. For example Electrically Erasable Programmable Read-Only Memory or EEPROM's, are memory chips where information is burned into the chip and will persist even after the loss of power or a reboot. Memory that can retain its information permanently is known as non-volatile memory.

ROM's and EEPROM's are important because they contain machine code instructions that basically jump start the computer. These instructions are also known as the Basic Input-Output System or BIOS. If these non-volatile memory chips did not exist in a computer, it would just sit there and do nothing when first powered on. (See the section titled BIOS below.)

[ history ]

BIOS

The Basic Input-Output System BIOS is responsible for initializing a computer system into a usable state. The primary task performed by the BIOS during startup is to check the status and initialize the most important sub-systems and peripherals in the computer system such as memory, the hard disk and more. Any problems that occur during startup are reported to the user. It also is responsible for initializing the operating system (See the section titled Operating System).