Page 24 - DCAP507_SYSTEM_SOFTWARE

System Software

Notes
Did u know? Operating systems in general, perform similar functions but may have
distinguishing features.
Operating systems can be classified into different categories on different bases. Let us quickly
look at the different types of operating systems.
Single User – Single Processing System

The simplest of all the computer systems is a single use-single processor system. It has a single
processor, runs a single program and interacts with a single user at a time. The operating system
for this system is very simple to design and implement. However, the CPU is not utilized to its
full potential, because it sits idle for most of the time.

Figure 2.1

Application user
program

operating system

hardware

In this configuration, all the computing resources are available to the user all the time. Therefore,
operating system has very simple responsibility.

Example: A representative example of this category of operating system is MS-DOS.

Batch Processing Systems

The main function of a batch processing system is to automatically keep executing one job to the
next job in the batch. The main idea behind a batch processing system is to reduce the interference
of the operator during the processing or execution of jobs by the computer. All functions of a
batch processing system are carried out by the batch monitor. The batch monitor permanently
resides in the low end of the main store. The current jobs out of the whole batch are executed in
the remaining storage area. In other words, a batch monitor is responsible for controlling all the
environment of the system operation. The batch monitor accepts batch initiation commands
from the operator, processes a job, performs the job of job termination and batch termination.
In a batch processing system, we generally make use of the term 'turn around time'. It is defined
as the time from which a user job is given to the time when its output is given back to the user.
This time includes the batch formation time, time taken to execute a batch, time taken to print
results and the time required to physically sort the printed outputs that belong to different jobs.
As the printing and sorting of the results is done for all the jobs of batch together, the turn
around time for a job becomes the function of the execution time requirement of all jobs in the
batch. You can reduce the turn around time for different jobs by recording the jobs or faster input
output media like magnetic tape or disk surfaces. It takes very less time to read a record from

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