Volatile memory needs to have power in order to function. This is because memory is implemented in terms of stored capacitance (DRAM), or requires an active bistable latch (SRAM). As soon as the power is removed, their ability to retain storage is lost. For example, a DRAM has a retention time of about 100ms.
The mains types of volatile memory are latches, flip-flops, SRAM and DRAM
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