Read Only Memory (ROM)
Read Only Memory (ROM) is a special type of non volatile memory that is used for certain functions, e.g. to store the computer system's Basic Input/Output System and also to store instructions that are required to be carried out when the computer is first switched on, e.g. Power On Self Test (POST). This test is used to check all of the hardware attached to the computer to see if it is working. If something fails the POST, e.g. a RAM fault, then the computer will issue a series of audible beeps. For each possible error there is a different set of beeps.
Once the computer has completed its POST it will look at its ROM and carry out the other instructions stored there. One of the key instructions is that to tell the computer to boot up the operating system.
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