C.P.U. Stands for central processing unit, the brains of the computer. Receives information, makes calculations, comparisons, alterations and transmits the results. Memory There are two basic types of memory: ''Read only memory'' (ROM) refers to knowledge permanently built into a computer. ''Random access memory'' (RAM) refers to the computer's capacity to store information while it is turned on. If the information is to be reviewed at a later time, it must be transferred to ''mass storage'' (see below); otherwise, the information will be lost when the computer is turned off.

Mass storage

An ordinary tape cassette deck can be used to store information. However, it has some distinct disadvantages: it can be very timeconsuming to transfer the information, and, if the recording is poor or if the tape stretches, the stored data may be lost. A more expensive, but more reliable, system, is disk storage. Disks look like 45-r.p.m. records, slip in and out of a vertical turnstile, and can record and recall information at very high speeds. Keyboard Designed like a standard typewriter keyboard, it permits the operator to tell the computer what to do. Terminal This is the video screen linked to the computer via the typewriter keyboard (see above). The screen allows a person to pose questions and read the computer's answers as well as display games and draw graphics. Computers have black-and-white or color screens or hook up to an ordinary television set. Modem A device that uses an ordinary telephone to connect one home computer with other computers, including several central computer services. These large ''data banks'' give consumers access to vast amounts of information, including news, movie reviews, stock prices and banking services. Subscribers, who pay hookup fees, can even write letters or converse (using their keyboards) with other subscribers. Graphics By using the keyboard or a kind of electronic sketch pad, a person can draw designs and pictures on the screen in color or black and white, depending on the terminal. Speech synthesis and music

Some computers have a device that converts written information into audio signals that mimic speech and music. Conversational courses in foreign languages, using the home television's speaker, are available, as are programs that permit the operator to write and listen to music. Printer Automatic typewriters that print paper records of computer activity, including calculations, letters, recipes. Since printers can cost as much as the computer, few homeowners buy them initially. Program Instructions given the computer to perform a specific task. The program is written in computer language. Programs are called software, to distinguish them from the physical hardware of the computer itself. In addition, firmware are programs that are permanently programmed into the computer's ''read only memory.'' Language The computer has two languages: an internal, machine language, which uses the binary system, stringing 1's and 0's together; and an external language, consisting of English letters, numbers and symbols. To translate from binary to English, a language program is needed.

Most home computers are programmed to understand BASIC (Beginners All-purpose Symbolic Instructional Code). BASIC allows the operator to communicate with the computer by typing English words and abbreviations into the keyboard. The BASIC program automatically translates them into assigned binary codes.