Random Access Memory

Random Access Memory (RAM) is a very common type of memory where any data can be accessed immediately, as opposed to sequential access memory, where the entire memory must be searched through in order to find the data desired. Typically, RAM also implies that the memory is read/write memory, but this is not strictly true.

Here is a simple model:

address +--------+
   bus  | Memory |
---/----|        |
   8    |  256   |
        | bytes  |
  data  |        |
   bus  |        |
---/----|        |
   8    |        |
        |        |
read/   |        |
 write  |        |
--------|        |
        +--------+

Here, the memory is internally divided into 256 bytes, each of which is a register holding 8 bits. Each of these registers can be accessed individually by placing the address of the byte upon the address bus. Then, depending upon the assertion level of the "read/write" line, the accessed byte will either have its data placed on the data bus, or will have the data on the data bus stored into it.

See also Read Only Memory, Flip-Flop, bus.