5.3.1 Computer memory
|Candidates are expected to be able
- identify the difference between
RAM and ROM, describing their
Internal memory is usually referred to as RAM
Memory) because data can be
stored and accessed from any area of the memory chip. It is usually
measured in mega-bytes (MB) so a typical desktop computer might be sold with
512MB of RAM.
All computers have
main/internal memory to store programs and
data while the computer is
running. This memory is in the form of memory chips and the contents are
lost when the computer is switched off (it
is also know as 'volatile' memory).
is a type of memory chip which only allows data to be
read from it. You cannot therefore change
the data stored on ROM. In a computer, ROM it is used often used to store
permanent programs and/or data needed to run the hardware. In an
embedded computer, such as
in a washing machine, the ROM stores the program that controls the machine. The contents of ROM are not lost (it
is 'non-volatile') when a computer is
The motherboard BIOS (Basic Input/Output System) memory chip typically
contains program code called firmware to access fundamental hardware components
such as the keyboard, floppy drives, ATA (IDE) hard disk controllers, USB human
interfaces, and storage devices. By providing access to the system hardware the
BIOS enables the running of higher-level operating systems (DOS, Windows etc.)
that are loaded from backing storage.
Early computer BIOS chips were ROM so the program could not be altered. As
the need for updates grew, hardware manufacturers needed to issue BIOS updates
to upgrade their products, improve compatibility and remove bugs. A modern
motherboard BIOS therefore is made up of ROM and RAM, a small battery on the
motherboard providing the power to maintain the contents of the RAM.