-Random access M (RAM) holds data, programs and part of the operating system currently in use
- often known as Immediate Access store (IAS)
- all data being used in programs needs to be transferred to the RAM
- Memory is made up of an address and its content; address identifies the location of data and instructions
- all memory location are unique
- primary memory also includes read-only memory (ROM) which cannot be altered, contains the start- up routines for the computer