Static RAM, SRAM:
The storage cells consist of bistable circuitry elements with a functionality similar to that of a flip-flop. The information is not volatile; it is stored until the storage element concerned is rewritten. SRAMs are significantly more expensive than DRAMs.
Memories made out of semiconductor elements which are generally integrated into computers as the main memory and used to prepare large volumes of data and programs.
A distinction is made between:
ROM:
Read-only memory. Memory content can be neither modified nor erased. Non-volatile type of memory. Programming via masks during fabrication.
RAM:
Random-access memory; volatile type of memory. Programming and erasure are performed electrically.
PROM:
Programmable read-only memory. Programming is performed electrically, erasure is not possible. Non-volatile type of memory.
Erasable programmable read-only memory; programming is performed electrically, erasure via UV light radiation. Non-volatile type of memory.
Electrically erasable programmable read-only memory; programming is performed electrically; non-volatile type of memory.
EAROM:
Electrically alterable read-only memory; programming is performed electrically, electrical erasure is also possible a word at a time. Non-volatile type of memory. Highly suitable for machine controls.
Dynamic RAM, DRAM:
The information appears as an electrical charge, which then leaks away again. To prevent it being lost, the charge is renewed at short intervals (of a few ms). This occurs automatically via the processor.
DRAM is currently available up to 1 Mbit.