computer memory

Understand different types of computer memory such as RAM (random-access memory), ROM (read-only memory) and distinguish between them

What is RAM

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 as you can afford to buy.
Commonly modern computers are supplied with over 128 MB of RAM. As a rough rule,
a Microsoft Windows based computer will operate faster if you install more RAM.
When adverts refer to a computer having 128 Mbytes of memory, it is this RAM
that they are talking about. Data and programs stored in RAM are volatile (i.e.
the information is lost when you switch off the computer).

What is ROM

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.

What is the ROM-BIOS

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.

What is flash BIOS

Most modern 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.

What is video (graphics) memory

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.