Read Only Memory - ROM is a special type of memory that contains instructions that are activated each time the computer is turned on.   These instructions are set at the time the computer is assembled and cannot be changed. ROM can only be "read", not written to. ROM chips are considered as Von-volatile memory. This means that the contents of the memory chip are retained even when the power is turned off.

  • One of the most important uses of the ROM chip is to store a series of programs that provide basic control of the computer. These programs together are called the "Basic Input/Output System" or BIOS.

  • These "BIOS" programs control the computer's startup processes and other basic components such as the keyboard, monitor/display, disk drives, etc.  The BIOS is always on a ROM Chip or version of ROM such as EPROM, etc.

The ROM may be in chips that look something like this:

ROM MEMORY is reserved for use by operating systems (DOS, Win95, NT, etc.), and hardware devices, BIOS, CMOS, etc. You cannot use this memory for applications such as MS-WORD, buffers, etc.

During system operation the ROM BIOS controls communications between the CPU, the Operating System and installed hardware.

The version of the ROM BIOS can be a key factor in whether your computer is compatable with certain hardware devices.

If the version is too old, you may not be able to use a hard disk larger than 4.5GB on your system without the aid of 3rd party software.