Time sharing versus batch

[1] The computer is a very expensive machine which is capable of executing 1
jobs at an extremely fast rate. Since computer time is very costly, time
sharing techniques were devised in order to use the central processing
unit more efficiently by leaving it idle as little as possible. These
techniques, of which multiprogramming is one, allow a number of users 5
to share the resources of the computer concurrently. Multiprogramming
is when more than one program can be present at different storage
locations of the memory at the same time. When the CPU needs to work
on a specific part of a program, it fetches it, processes it and, while the
results are being printed or being stored on an on-line disk, the CPU 10

fetches a part of another or the same program for processing. Consequently, although only one program is being executed at any one time, it is as though the CPU is working on various programs simultaneously. What actually happens is that the CPU is kept in action while programming operations, such as printing, are being carried out. 15 The means by which the computer knows which programs to work on is determined by its operating system, which schedules and monitors the various programs being processed simultaneously.

[2] Computer systems capable of time sharing programs facilitate real time

programming, which means that a user can interact with the computer 20
by asking it to perform a desired task and have the task completed
within a matter of seconds. An example of this is when an airline ticket
reservation clerk, using a terminal, asks the computer about the
availability of seats on a certain flight. In a few seconds the computer,
having checked its updated data bank, gives back the answer. 25

[3] In real time processing, the user doesn't have to wait long to receive
answers to his other questions. Moreover, an up-to-date view of the
situation is provided. In contrast to real time processing, batch
processing is done on programs which do not require interaction with
the computer from a terminal, and which may involve lengthy input, 30

output, and processing. Rather than being keyed in from a terminal, the input may come from cards, disk, or tape, while the output is usually on a high-speed printer. An example of a batch job is a computerized company payroll system.

Exercises

Main idea

Which statement best expresses the main idea of the text? Why did you

eliminate the other choices?

1. Multiprogramming is a very efficient technique for using the

central processing unit.

2. There are basically two ways of processing information by the

computer: real time and batch mode.

3. Real time programming requires that information in data banks

be constantly updated.

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