Evolution of Operating Systems

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Serial Processing:

– No operating system

• Machines run from a console with display lights, toggle switches, input device, and printer

• Schedule time, e.g. sign up

• Setup included loading the compiler and source program, saving compiled program, loading and linking

• Simple Batch Systems

– Monitor

• Software that controls the sequence of events

• Batch jobs together

• Program branches back to monitor when Finished

Job Control Language (JCL)

• Special type of programming language

• Provides instruction to the monitor, e.g.

– What compiler to use

– What data to use

· Uniprogramming

• Processor must wait for I/O instruction to complete before preceding


· Multiprogramming

• When one job needs to wait for I/O, the processor can switch to the other job


· Time Sharing

• Using multiprogramming to handle multiple interactive jobs

• Processor’s time is shared among multiple users

• Multiple users simultaneously access the system through terminals

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