Personal
computers are supposed to appear in the late 1970s. One of the first and
most popular personal computers was the Apple II, introduced in 1977 by
Apple Computer. During the late 1970s and early 1980s, new models and
competitive operating systems seemed to appear daily. Then, in 1981, IBM
entered the fray with its first personal computer, known as the IBM PC. The
IBM PC quickly became the personal computer of choice, and most other
personal computer manufacturers fell by the way-side. One of the few
companies to survive IBM’s onslaught was Apple Computer, which is sure to
remain a major player in the personal computer marketplace. In less than a
decade the microcomputer has been transformed from a calculator and
hobbyist’s toy into a personal computer for almost everyone.
What is a personal computer? How can this device be characterized?
First, a personal computer being microprocessor-based,
its central processing unit, called
a microprocessor unit, or MPU, is concentrated on a single silicon chip.
Second, a PC has a memory and word size that are smaller than those of
minicomputers and large computers. Typical word sizes are 8 or 16 bits, and
main memories range in size from 16
Ê
to 512 K.
Third, a personal computer uses smaller, less expensive, and less powerful
input, output and storage components than do large computer systems. Most
often, input is by means of a keyboard, soft-copy output being displayed on
a cathode-ray tube screen. Hard-copy output is produced on a low-speed
character printer.
A PC employs floppy disks as the principal online and offline storage
devices and also as input and output me dia.
Finally, a PC is a general-purpose, stand-alone system that can begin to
work when plugged in and be moved from place to place. Probably the most distinguishing feature of a personal computer is that it is used by an individual, usually in an interactive mode. Regardless of the purpose for which it is used, either for leisure activities in the home or for business applications in the office, we can consider it to be a personal computer. |