Random-access memory (RAM) is a volatile form of semiconductor data storage for computer and other electronics. Information stored in this kind of memory can be accessed and modified very quickly. However, a small amount of constant power is required to retain information. For these reasons, it is generally used as temporary memory, which contains variables and values used by the operating system and other software for a short time. Any valuable information stored in RAM must be copied to non-volatile memory (which does not require power to retain information) before power is disconnected from the RAM, since the RAM resets when powered off.
RAM chips have continued to improve over time. As a result, there are a number of varieties of RAM, which are not reverse or forward compatible. Therefore, a newer computer using DDR3 could not use DDR2 from an older device.