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Unformatted text preview: batch processing system.
Notice from the figure that in order to distinguish a control card from data or
program cards, they are identified by a special character or pattern on the card.
Several systems used the dollar-sign character ($) in the first column to identify a
control card, while IBM's JCL used slash marks (//) in the first two columns. Other
systems used some other characters or codes. The basic idea in selection of these
special characters or codes was that no program or data card should have these
characters or code.
Data for program
$JOB, ONGC05839, USER=SINHA
In case of both manual loading and batch processing of jobs, the jobs are loaded
into the system and processed one at a time. That is, once loaded, a job will remain
in the main memory until its execution is completed and the next job will be
loaded only after the completion of the previous job. As shown in Figure 14.3, in
such a situation, the job which is currently loaded and is being executed will be the
sole occupant of the user's area of the main memory (the operating system always
resides in a part of the main memory) and it will have the CPU exclusively
available for itself. The situation shown in Figure 14.3 is that of a uniprogramming
system in which only one job is processed by the system at a time and all the
system resources are exclusively available for the job until it completes.
It was observed that a job does not need the CPU for the entire duration of its
processing. This is because in addition to doing computation (for which CPU is
needed), a job often needs to perform I/O operations (such as reading or writing
some data to a tape or disk, waiting for some data to be input from the keyboard,
and printing some results) during the course of its processing. In fact, depending
on the CPU utilization during the course of processing, jobs are broadly classified
into the following two types: 1. CPU-bound jobs. These jobs mostly perf...
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This document was uploaded on 04/07/2014.
- Spring '14