The basic idea in selection of these special

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: itted batch were processed, the operator would separate the printed output for each job and keep them at the reception counter so that the programmers could collect them later. The batch processing mechanism helped in reducing the idle time of a computer system to a great extent because transition from one job to another did not require any operator intervention. Another major time saving made possible by batch processing was reduction in set-up time by batching of similar jobs together by the operator. For example, if all FORTRAN compilation jobs are batched together, the system needs to load the FORTRAN compiler only once for processing all these jobs. The obvious question is how the computer separates one job from another from a batch of jobs for automatic job-to-job transition. Moreover, how does the system know which compiler or what hardware devices are to be used by a particular job when there is no operator intervention? To facilitate all these, control statements and job control languages (JCLs) were introduced along with the concept of batch processing. The control statements are used by the operating system to identify a new job and to determine what resources are needed by the job during its execution. These control statements are written in a language known as the job control language. Usually every program and data sets are preceded and followed by JCL statements. When a program is prepared for a computer run, it is necessary to prepare the job control statements and place them in proper order along with the program, before the program is fed to the computer system. Thus, each program has, besides the program itself, a set of instructions called JCL instructions, which instruct the operating system on the identity and requirements of the job. JCL statements tell the operating system things such as the name of the job, the user's name and account number, the I/O devices to be used during processing, the assembler or compiler to be used if language translation is required, and so on. Figure 14.2 shows a sample deck of cards prepared for the compilation and execution of a COBOL program in a...
View Full Document

This document was uploaded on 04/07/2014.

Ask a homework question - tutors are online