Disadvantages Of Serial Processing Operating System

Example of serial processing operating system Any operating system running on the single processor is an example of the serial operating system. Note that one processor complete one task at a given time and other tasks wait in a queue. In an operating system, there may be running multiple programs and each program has multiple tasks running.

Batch processing Batch processing is a technique in which an Operating System collects the programs and data together in a batch before processing starts. An operating system does the following activities related to batch processing − • The OS defines a job which has predefined sequence of commands, programs and data as a single unit.

• The OS keeps a number a jobs in memory and executes them without any manual information. • Jobs are processed in the order of submission, i.e., first come first served fashion. • When a job completes its execution, its memory is released and the output for the job gets copied into an output spool for later printing or processing. Advantages • Batch processing takes much of the work of the operator to the computer. • Increased performance as a new job get started as soon as the previous job is finished, without any manual intervention.

Disadvantages • Difficult to debug program. • A job could enter an infinite loop. • Due to lack of protection scheme, one batch job can affect pending jobs. Multitasking Multitasking is when multiple jobs are executed by the CPU simultaneously by switching between them.

Switches occur so frequently that the users may interact with each program while it is running. An OS does the following activities related to multitasking − • The user gives instructions to the operating system or to a program directly, and receives an immediate response.

• The OS handles multitasking in the way that it can handle multiple operations/executes multiple programs at a time. • Multitasking Operating Systems are also known as Time-sharing systems. • These Operating Systems were developed to provide interactive use of a computer system at a reasonable cost. • A time-shared operating system uses the concept of CPU scheduling and multiprogramming to provide each user with a small portion of a time-shared CPU. • Each user has at least one separate program in memory.

• A program that is loaded into memory and is executing is commonly referred to as a process. • When a process executes, it typically executes for only a very short time before it either finishes or needs to perform I/O. • Since interactive I/O typically runs at slower speeds, it may take a long time to complete. During this time, a CPU can be utilized by another process.

• The operating system allows the users to share the computer simultaneously. Since each action or command in a time-shared system tends to be short, only a little CPU time is needed for each user. • As the system switches CPU rapidly from one user/program to the next, each user is given the impression that he/she has his/her own CPU, whereas actually one CPU is being shared among many users. Multiprogramming Sharing the processor, when two or more programs reside in memory at the same time, is referred as multiprogramming. Multiprogramming assumes a single shared processor. Multiprogramming increases CPU utilization by organizing jobs so that the CPU always has one to execute.