• Less expensive per unit than primary memory. Quick yak: Secondary storage can be illustrated by examples on • Books • Note books • Telephone book etc.
©LPU CSE101 C Programming Operating System • Operating systems A collection of programs that manages resources of a computer, such as - processors - memory - input/output devices – Perform basic tasks – Manage transitions between jobs – Increased throughput • Amount of work computers process • Multiprogramming – Many jobs or tasks sharing a computer’s resources – “Simultaneous” operation of many jobs. • Timesharing – Perform a small portion of one user’s job then moves on to service the next user
©LPU CSE101 C Programming Batch Processing systems • First computer used batch OS in which computer ran batches of jobs without stop. • A 'batch' is the name given to the task of doing the same job over and over again • Programs were punched into card that were copied to tape for processing. • OS runs the series of jobs sequentially without user intervention. • When computer finished one job it would immediately start next one on tape.
©LPU CSE101 C Programming Batch Operating Systems • Jobs, together with input data, are fed into the system in a batch. • The jobs are then run one after another. • No job can be started until previous job is completed
©LPU CSE101 C Programming The Advantages of batch based systems: • Significant savings • Reproducibility / elimination of human error • Transference of computer workload from prime (expensive) daytime to cheaper overnight off-peak times.
©LPU CSE101 C Programming The Disadvantages of batch based systems 1. Lack of interaction between the user and job. 2. Inconvenient for users as users not interacted with machine. Only professional operator used this for stream. 3. CPU is often idle, because the speeds of the mechanical I/O devices is slower than CPU. • Examples of batch operating system are as follows: 1) DOS (Disk operating system) 2) IBM OS/2 3) Windows 1,2,3 95, 98 and ME
©LPU CSE101 C Programming Time sharing Operating Systems • In 1960’s time shared replaced batch OS. • It allows many users to share the computer resources simultaneously. • Each user is given a time slice to interact with the CPU. • The size of the time slice will depend on the system. • Each user is served in sequence.
©LPU CSE101 C Programming Example
©LPU CSE101 C Programming • Advantages of Timesharing operating systems • Provide advantage of quick response. • Reduces CPU idle time. • Disadvantages of Timesharing operating systems • Problem of reliability. • Question of security and integrity of user programs and data. • Problem of data communication.
©LPU CSE101 C Programming Generations of Operating System Operating systems have evolved through a number of distinct phases or generations : • First Generation • Second Generation • Third Generation • Fourth Generation • Fifth Generation
©LPU CSE101 C Programming Generation Duration Memory Device Features Example First (No operating system) 1942-1955 Vacuum Tubes or Valves used vacuum tubes as electronic circuit magnetic drum for primary storage punch-card used as secondary storage machine level programming used operating speed was used in terms of millisecond Mark-I, UNIVAC, ENIAC etc.
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