Memory
As opposed to hard drives, this memory is volatile and will be cleared when a computer powers down. It is theoretically possible for computers to function without RAM, by software only using the stack for data storage. However, typically software requires RAM to function. In particular, the firmware contained in newly obtained computers requires a decent amount to function.
How much memory is needed depends on the operating system. OpenOS II runs with a single 2M module, Linux needs at least 8M. The Z80 processor has memory built in, so CP/M needs no module. Also see the getting started manual entry.
Computers have to be shut down before installing or removing this component. Installing it while the computer is running will have no effect, removing it may lead to system errors.