•	Main memory contents can be accessed directly by the CPU. It has very fast access times and it has a relatively small capacity.
•	The contents of RAM are lost when the computer is turned off (volatile). The contents of ROM are retained (non-volatile).
•	ROM is memory that cannot be changed by a program or user. It retains its memory even after the computer is turned off. It is used to store the instructions for the computer to boot up when it is turned on. It is also used to store software that needs to be available when the computer is turned on (such as the instructions for booting the computer) or software that will ‘never’ change such as the BIOS. With Von Neumann architecture the program(s) being run are kept in the computer memory as well as the data that is currently being processed.
•	RAM is a fast temporary type of memory in which programs, applications and data are held.