Batch Processing

When the entire computer system is dedicated to a single job, the system is said to be operating in Batch Processing mode. In this mode each program is run to a conclusion once it is initiated, and other programs have to wait in a queue. Batch Processing was used in all earlier generations of computers. It has the following shortcomings:

1. The Central Processing Unit (CPU) will not be utilized efficiently. For example, if a program calls for input or output operations, the CPU will remain idle during this operation. It is found that for commercial application the CPU efficiency may be as low as 35% in batch processing mode.
2. Batch processing may result in an unnecessarily large elapsed time interval between submitting a program and return of the results. This elapsed time is referred to as the turnaround time. This is because jobs have to wait till the earlier jobs in the queue are fully completed.