Read Only Memory (ROM)

1. Stores instructions that are used by the CPU
• Tells the CPU how to be the kind of computer it is, for example a Windows, Macintosh, or Play Station computers.
• Tells the CPU how to work with the different parts of the computer
• ROM can also hold programs that are directly accessed by the CPU.  One such program is the self-test when the computer is first turned on.  The self-test tests to seem if all the parts on the main circuit board (mother board) are working correctly.
2. The instructions in ROM can not usually be changed
• The instructions are built into the electronic circuits of the chips
• These instructions in ROM are called firmware
• To change the instructions in ROM you need to usually change the chips or do some other special process that is normally not available to an average user.
3. The instructions in ROM are nonvolatile.  They stay in ROM even when the computer is turned off.
4. Access to information is random access.
• Random access means that any piece of information in ROM can be accessed at any given time without access other information first.  It is a lot like the tracks on a music CD.  You can access any track at any time and in any order.
• The other kind of access is sequential access.  You must access the information in the order that they are located.  This is a lot like a music tape.  You must play the songs in order, or you have to fast forward past songs to get to the one you want.