What exactly is computer memory? Is it the disk? Is it RAM or ROM?

First of all, sometimes the term "memory" is used in conjunction with the storage of data magnetically on hard or floppy disks. This is incorrect. Magnetic data storage on disks is not memory. Computer memory consists of electronic chips installed in sockets on the main circuit board thatís inside your computerís case. Two kinds of memory are used in personal computers -- ROM and RAM.

ROM stands for "Read Only Memory." Data is permanently stored in a ROM chip. It can only be read, or "played back," and no new data can be written, or "recorded." This is analogous to an audio CD, which can play back but canít record music. ROM is used to store setup and initialization data which the computer needs to properly start up, or "boot.'

The second kind of PC memory is RAM, which stands for "Random Access Memory." These types of chips are like a cassette deck, in that data can be temporarily recorded, played back, and erased during your computing session. When you run a program, the computer instructions that make up the program are copied to the RAM chips. Data that you generate as you use the program is also temporarily kept in RAM. When you save your data and exit the program, the data is copied from the RAM chips to a disk (either hard or floppy, depending on your personal routine) and the program instructions are erased. RAM is also called "volatile" memory, because it only holds data as long as it is energized by electricity. This means you can kiss your data good-bye if the document youíre writing or the spreadsheet youíre working on hasnít yet been saved to disk, and a power failure occurs; or you make a mysterious move that locks up the keyboard, and youíre forced to restart the computer. Sound like a reason to save data frequently? I donít think I need to draw you a diagRAM to illustrate the RAMifications of not pROMptly saving data when it changes significantly fROM time to time.

K.O.P.C.Online home > table of contents > memory