Random Access
Memory (RAM)
is the main 'working' memory used by the computer. When the operating
system loads from disk when you first switch on the computer, it is
copied into RAM. The original IBM PC could only use up to 640 KB of
memory (just over half a megabyte), whereas a modern computer can effectively
house as much RAM is you can afford to buy! Commonly 2009 computers
are supplied with over 1Gigabyte of RAM. As a rough rule, a Microsoft
Windows based computer will operate faster if you install more RAM.Data
and programs stored in RAM are volatile (i.e. the information is lost
when you switch off the computer).
Read Only Memory (ROM) as the name suggests
is a special type of memory chip that holds software that can be read
but not written to. A good example is the ROM-BIOS chip, which contains
read-only software. Often network cards and video cards also contain
ROM chips.
The 'Read Only Memory Basic Input Output System'
chip is a chip located on the computer's system (mother) board, which
contains software. This software performs a variety of tasks. When you
first switch on the computer the ROM-BIOS
software performs a self-diagnostic to check that the computer is working
OK. This software then loads your operating system from the disk into
the RAM.
Now computers are actually supplied with a
flash BIOS rather than a ROM-BIOS. This chip contains exactly
the same type of in-built software, but has the advantage that the software
on the chip can be upgraded. This upgrade is achieved by simply running
a small program supplied by the computer manufacturer.
The picture that you see on your screen is
a form of data and this data has to be stored somewhere. The on-screen
pictures are held in special memory chips called video memory chips,
these chips are usually located on the video card. A modern computer
will be supplied with several Megabytes of video
memory.
