The job was in the form of punch cards and at some

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Unformatted text preview: ob was in the form of punch cards, and at some later time the output was generated by the system— user didn’t get to interact with his/her job. The output consisted of the result of the program, as well as a dump of the final memory and register contents for debugging. To speed up processing, operators batched together jobs with similar needs, and ran them through the computer as a group. For example, all FORTRAN programs were complied one after the other. The major task of such an operating system was to transfer control automatically from one job to the next. In this execution environment, the CPU is often idle because the speeds of the mechanical I/O devices such as a tape drive are slower than that of electronic devices. Such systems in which the user does n get to ot interact with his/her jobs and jobs with similar needs are executed in a “batch”, one after the other, are known as batch systems . Digital Equipment Corporation’s VMS is an example of a batch operating system. Figure 2.1 shows the memory layout of a typical computer system, with the system space containing operating system code and data currently in use and the user space containing user programs (processes). In case of a batch system, the user space contains one process at a time because only one process is executing at a given time. Figure 2.1 Memory partitioned into user and system spaces Multi-programmed Systems Multi-programming increases CPU utilization by organizing jobs so that the CPU always has one to ex...
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