Batch Operating System
Batch Operating System – Computer were extremely large machines in early times which run from console. Generally, devices used for I/O were tape driver or card readers for input and tape derives, punch cards and line printers for output. Users did not have direct interaction with system and execution of jobs were done in batched system this kinds of systems called as batched operating systems in which user have to prepare a jo separately to get them executed. There are two types of batched system
- Simple batched system
- Multiprogrammed batched system
Simple Batched System
In simple batch operating system user did not directly interact with computer system for job execution rather, the user required to prepare a job which entailed of the program the control information and data about the nature of job the control cards. Then this job was submitted to the computer operator which were usually in the form of punch card. Output appeared after some time it may took minutes, hours or days. The output of the program was consisted of results as well as registers and dumps of memory in case of program errors.
Its main task was to transfer the control from one job to the next in automatic manners. To enhance the processing speed jobs with similar needs were bathed together and were run as a group through the processor. The programmers used the operators in programs to make the batches with similar requirements. Computer run the batches one by one when it became available. This system usually reads a stream of separate jobs and each has its own control cads with predefined job’s task.
The delay in turnaround time may result from the amount of computing needed or from delays before the operating system starts to process a job. In this case of execution environment, the CPU is often idle. spooling process were used to pint the output from the line printer in which card reader was used to take the input and disk is use copy the command into system buffer and written to the disk CPU read command from dick execute it and send back to disk then ultimately output is printed at line printer.
Multiprogrammed Batched System
Spooling deals with several jobs that have already been read waiting on disk ready to run. Disk which contains a pool of jobs allows operating system to select job to run next for sack of CPU’s proper utilization. When jobs come in direct manner on magnetic tape or cards jobs cannot run in a different order. Jobs execute on the bases of first come, first serve so they must run in sequential fashion. Jobs scheduling become possible when several jobs are on a direct access device such as disk. The main characteristic of job scheduling is the ability to multiprogram. Spooling and offline operations for overlapped I/O have their limitations. In general, a single user cannot keep the I/O devices and CPU buys at all time.
In this case jobs are organized in such a way that CPU execute one job at a time to increase the CPU utilization. Several jobs are kept by operating system in memory at a time. Operating system pick the one job and begin to execute it in the memory. Ultimately the job has to wait for some task such as a tape to be mounted on an I/O operation to complete. In case of multiprogramming system do not sit idle because operating system switches to another job. Whenever on job is on wait condition and current job finished then it gets the CPU back.
Multiprogramming operating system is very sophisticated because it must make decisions for the user.