A Brief History Of The Operating System | brieflynotes

 A Brief History Of The Operating System

In the beginning, programs were run one at a time. In order to use CPU more efficiently, jobs of similar nature were grouped and made to run in batches. But after program execution, the computer operator manually restarted the next program. To avoid the delay due to manual operation, Automatic Job Sequencing mechanism was introduced. This is called Resident Monitor and this may be the first elementary operating system. If scientific applications had been used in a computer, the CPU was busy with the program, but if business problems had been handled, I/O system was busy and the CPU kept idle.

In order to make the CPU busy, the I/O operations were done in an inexpensive computer, the contents of card reader was transferred in a magnetic tape and which in turn was placed in the computer that performed the business operation. in those days data were stored in cards called punched cards. The next input might be ready in the buffer before the CPU processed the earlier data. When the processing was completed, the CPU sent the Output to the buffer. When the data were ready, an interrupt mechanism interrupted the CPU. The CPU having taken the necessary actions and resumed its original work. At the same time, DMA(Direct Memory Access) mechanism was also created, which allowed transferring data to and from memory without the intervention of the CPU. 



Spooling is a superior to the buffer, because in spooling I/O operations can be overlapped with the working of other jobs but that is not possible with the buffer. While executing one job, the OS, reads next job from card reader into a storage area on the disk and outputs printout of previous job from disk to the printer. Spooling allowed the CPU to choose a particular job for execution leading to the concept called the Job scheduling. The job scheduling led to the concept known as Multi programming. In multi programming, memory is dived into many partitions. multi programming allows many programming was followed by Time sharing concept. Here the CPU allocated a fixed time for each program. In the next cycle, the program that had been considered earlier was taken once again. This process continued until all the programs were executed.

Main Features of the Operating System

As per the number of users, there are two types of the operating systems. they are
  1.  Single User Operating System
  2.  Multi-User Operating System
Single User Operating System

At a time, only one user can operate the system, MS Disk Operating System is an example of Single User Operating System.

Multi-User Operating System:

More than one user operate the same system simultaneously. The multi user Operating System is based on the concept of time-sharing. Unix is an example of Multi-User Operating System.


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