Page 13 - DCAP103_Principle of operating system

Principles of Operating Systems
Notes
6 LOVELY PROFESSIONAL UNIVERSITY
personal computer of the late 1990s could easily outperform the advanced minicomputers of
that era. Since the terms “personal computer” and “PC” have been introduced to vernacular
language, their meanings and scope have changed somewhat. The first generations of personal
microcomputers were usually sold as kits or merely instructions, and required a somewhat
skilled person to assemble and operate them. These were usually called microcomputers, but
personal computer was also used. Later generations were sometimes interchangeably called by
the names “home computer” and “personal computer”. By the mid-1980s, “home computer” was
becoming a less common label in favour of “personal computer”. These computers were pre-
assembled and required little to no technical knowledge to operate. In today’s common usage,
personal computer and PC usually indicate an IBM PC compatible. Because of this association,
some manufacturers of personal computers that are not IBM PCs avoid explicitly using the terms
to describe their products. Mostly, the term PC is used to describe personal computers that use
Microsoft Windows operating systems.
Figure 1.2: Random-Access Memory
A four-megabyte RAM card measuring about 22 by 15 inches; made for the VAX 8600
minicomputer (circa 1986). Dual in-line package (DIP) Integrated circuits populate nearly the
whole board; the RAM chips are in the majority located in the rectangular areas to the left
and right. One early use of “personal computer” appeared in a 3 November 1962, New York
Times article reporting John W. Mauchly’s vision of future computing as detailed at a recent
meeting of the American Institute of Industrial Engineers. Mauchly stated, “There is no reason
to suppose the average boy or girl cannot be master of a personal computer.” Some of the
first computers that might be called “personal” were early minicomputers such as the LINC
and PDP-8. By today’s standards they were very large (about the size of a refrigerator) and
cost-prohibitive (typically tens of thousands of US dollars), and thus were rarely purchased
by an individual. However, they were much smaller, less expensive, and generally simpler to
operate than many of the mainframe computers of the time. Therefore, they were accessible for
individual laboratories and research projects. Minicomputers largely freed these organizations
from the batch processing and bureaucracy of a commercial or university computing centre. In
addition, minicomputers were relatively interactive and soon had their own operating systems.
Eventually, the minicomputer included VAX and larger minicomputers from Data General,
Prime, and others. The minicomputer era largely was a precursor to personal computer usage
and an intermediary step from mainframes.