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Computer Science by Ian Sinclair

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Computers and programs
same time for any reason other than a total failure of power. The micro also
ensures greater confidentiality of data., because the user can keep confidential
records on a disk which can be carried about, with no central records kept on
a machine to which many others have access. Though micros can be
operated with timesharing and in networks, in which several computers
share data stores and printers, the greatest advantage of the micro is obtained
when it is used as a stand-alone machine, and the use of modems to link
machines through telephone lines makes it possible for the first time to have
work done anywhere, bringing the promise of an end to the business of
moving thousands of people twice a day to sit at a desk and press keys which
they could press on a similar computer at home.
Exercise 1
Discuss the probable computing needs of:
(a) a small hardware store
(b) an agent for a mail-order catalogue
(c) the mail-order catalogue company
(d) a technical college
Computing work
One application of computers which is still a major requirement is numerical
processing. The solution of problems in engineering and science, par-
ticularly examples like the stresses on bridges, the path of airliners, the
positions of planets and weather forecasting all demand equations to be
solved at a rate of up to several millions p*er second. This calls for very fast
processing, and the speed of a computer for such work is measured in a unit
called the megaflop - the number of millions of floating-point arithmetic
operations per second. Work at megaflop speeds requires the use of
specialized mainframes, and for less intensive work, a minicomputer can
cope.
The most recent generation of microcomputers are also capable of
respectable rates of data processing, making them suitable for numerical
work.
Apart from the suitability of the machine, the program that is being used
has to be capable of high performance. The program must be written in a
language that allows for fast arithmetic, and languages are far from equal in
this respect. Some languages allow for this type of work to be carried out by
subprograms that are written in a faster language (assembly language),
others can make use of specialized co-processors. A co-processor is an
extension to a computer circuit that consist of a specialized plug-in module
which will deal with calculations separately, allowing the main unit to
concentrate on input and output. The use of a co-processor can often speed
up arithmetical work by ten to thirty times, depending on the application. In
the earlier days of programming, a programming language called
31

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