Describe briefly about the major types of random memory?

Answer 1

The most common type of RAM is 'dynamic' RAM, so named because the information is stored as a charge on small capacitors on the chip. This charge tends to 'leak' through het sourounding semiconductor memory and must be 'refreshed' periodically adn so the memory is constantly running, even when the CPU is not requestion that anything be read out or stored.
The next most common type is calles 'static' RAM and is so named because each 'bit' of information is actually stored in the state of a 'flip-flop' (or bistable multivibrator) circuit. This type of ram doesn't need to be constantly refreshed and so uses very little power when not being read or written to.
The least common type of RAM (which is also one of the very first types of 'high-speed' memory) is called 'core' memory. In core memory, the information is stored in the magnetization of a small ferrite toroid (or 'doughnut') and read out by supplying currents to cause the magnetization state to 'flip' and generate a small pulse of voltage. This type of RAM tends to be fairly slow (800 nS or so) but it has the great advantage that it can store data with absolutely no external power. It is still used in some deep-space probes for that reason.

HTH

Doug