There are many types of microcomputers. Here, we will use an IBM Personal Computer (PC) to illustrate the primary components of a microcomputer. Other brands and models of microcomputers exhibit difference in appearance and operations. An IBM PC is shown in the figure. Its primary hardware components are the main frame, the monitor, the keyboard, and many peripherals such as the disk drive, hard disk, printer, and mouse, all of which are hardwired to the main frame. The main frame is the heart of a microcomputer system. It contains the Central Processing Unit (CPU), a chip that controls the major operations of the computer and the main memory.
The typical secondary storage medium of a microcomputer is the floppy and hard disks. A floppy disk, or diskette, is a thin circular piece of flexible polyester coated with a magnetic material. The data are recorded on a series of concentric circles called tracks. The access mechanism steps from track to track, reading or writing one track at a time. A track is subdivided into sectors. To distinguish the sectors, they are sequentially addressed by natural numbers 0,1,2and so on .A sector is a primitive access unit.Most microcomputers use floppy diskettes of 5 1/4 inches and 3 1/2inches in diameter. The following figure shows a 3 1/2 inches floppy diskette. Hard disks, or fixed disks, can be either fixed in the mainframe as a part of the internal hard disks reside permanently within the microcomputer and are removed only for servicing or replacement. External hard disks can be purchased alone and then attached to the microcomputer with cables; they are used for backing up large amounts of data or for additional storage capacity. Hard disks provide tremendous storage capacities ranging from hundreds of megabytes to several gigabytes.