The Central Memory

The central memory, also called random access memory (RAM) or direct access memory, is a volatile memory. It is the memory you use for writing and reading. The information it contains disappears
when the central unit is switched off. RAM can be used directly by the microprocessor. This memory is measured in thousands of characters.

The unit of memory measurement is the byte, also called a character.
1 kb = 1024 characters (bytes)
1 Mb = 1024 × 1024 characters (bytes)
1 Gb = 1024 × 1024 × 1024 characters (bytes)

To run Windows 3.1, your PC requires a minimum of 2 Mb of RAM.
To run Windows 95, your PC requires a minimum of 16 Mb of RAM.
To run Windows 98, your PC requires a minimum of 24 Mb of RAM.

The RAM capacity of a standard PC is between 128 Mb and 512 Mb of RAM.
The RAM linear arrays are plugged into memory expansion slots. If you go to a shop to buy more basic memory for your PC, you will probably be asked if you want additional linear arrays of 4, 8, 16,
32, 64 or 128 Mb. You will be asked if you want a particular speed to match that of your currently installed memory. This is usually too complicated for most users, even those with some experience
of computers. For some time, the trend has been towards simplification, especially when you are equipped with standard hardware. A reputable dealer should be able to advise you on your purchase.

Division of the RAM

The RAM is divided into three main categories:

• Conventional memory: memory consisting of the first 640 kb.

• Upper memory: memory situated between the conventional memory and the first megabyte (from 640 to 1024 kb).

• Extended or high memory: memory situated beyond the first megabyte (above 1024 Mb).

There is another category that merits special attention. Memory between 64 and 128 Mb creates problems for certain top-ofthe- range configurations. There is a bug that, under certain conditions,
drastically reduces computer performance. Fortunately it affects only Windows 95 machines and has been eradicated in Windows 98.