A videotex keyboard terminal can be connected to a telephone jack and any television set. The user can request and receive any kind of information stored in the central computer. Some of the online services use this type of equipment (see section about online information systems on page 20). Many farmers are also using handheld programmable calculators. These are convenient to use in the field, and can record often repeated data, such as daily milk production. They have little memory (usually 2K) and their output can be printed on 2-inch paper tape. They are much cheaper than the microcomputer. Farmers use them to record daily milk production, formulate dairy and beef rations, estimate value of dairy forages, estimate cost of operating farm machinery, and calculate depreciation and investment tax credit. Some very large farm operations use minicomputers, which are larger, have more memory, can do more functions than the microcomputers, and can support multiple users. However, the newer microcomputers have more memory and more functions, and the difference between minicomputers and microcomputers has narrowed. =Computer System Components= [Illustration: Printer; Display Screen; Telephone/Modem; Disk Drive; Floppy Disk; and Central Processor with Keyboard] =Components of a Microcomputer= One way to understand how a microcomputer works is to see its key components. The =central processing unit= (CPU) is the silicon chip that is the "brain" of the computer. It does all the computation and controls all the other processing. The CPU stores =memory= of several kinds. Part of the memory is wired into the computer permanently by the manufacturer. This is called Read Only Memory (ROM). It contains such things as the operating system and program language. Random Access Memory (RAM) is the memory bank that includes the computer program or instructions, as well as the data. Your storage devices--tape cassettes, floppy disks, or hard disks--that store computer programs and data, are sometimes called external memory. The computer system also needs =input devices= and =output devices=. Your keyboard is an input device; disk drives and tape drives are also input devices. The output will probably be a cathode ray tube (CRT), which looks like a video monitor. The printer is the other output device you may choose to include in your computer system. Make sure the microcomputer has an adequate number of input and output ports for future needs. If you use your computer for communications, you'll need a telephone =modem=. Here is a possible shopping list of hardware for a farmer's starting microcomputer system: CPU (computer) with 48K or 64K of memory. CRT or monitor with adequate character width for the programs you plan to use. One or two disk drives, either 5¼ or 8 inches in diameter. Dot matrix printer (optional). Modem for communication with large computer (optional). =Try it Out=