RAM memories may be made out of flip-flops, using gates, but this is often too expensive. Such RAM is called SRAM or static RAM because the values in the memory cells stay around (are static) as long as the power is on. Some cache memories used SRAM, but they are both expensive and use a lot of chip real estate.

The main RAM of the computer, the figure heard when a salesperson boasts that this new model has 16 Megabytes of RAM, for instance, is usually of DRAM, or dynamic RAM. This technology breaks a chip surface into millions of small squares which function as capacitors, each storing 1 bit of information.