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Principles of Operating System and Software application

Principles of Operating System and Software application. Prepared by Ms. Loren Chavez. Lesson Overview. What is an operating system? Brief history of operating systems Activity. The operating system is the software layer between the user applications and the hardware.

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Principles of Operating System and Software application

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  1. Principles of Operating System and Software application Prepared by Ms. Loren Chavez

  2. Lesson Overview • What is an operating system? • Brief history of operating systems • Activity

  3. The operating system is the software layer between the user applications and the hardware. • The OS is “all the code that you didn’t have to write” to implement your application.

  4. Brief History of O.S. …..

  5. In the beginning… • OSeswere runtime libraries The OS was just code you linked with your program and loaded into the computer. • First computer interface was switches and lights, then punched tape and cards.

  6. Back in the transistor-based technology, early mainframes were first run by human operators. The unit of processing was a job, or predefined collection of commands that are executed without human interaction. Operators would handle one job at a time (e.g., submitting punch cards, running the program, and printing out results). Much computer time was wasted.

  7. Later machines came with libraries of programs, which would be linked to a user's program to assist in operations such as input and output and generating computer code from human-readable symbolic code. • This was the genesis of the modern-day computer system. However, machines still ran a single job at a time.

  8. Batch systems were next… • OS was permanently stored in primary memory • It loads a single job into memory(card reader, magnetic tape); • Executes job, creates output (line printer); • Loaded the next job, so on and so forth… • Card readers, line printers were slow, and CPU was idle while they were being used.

  9. Batch system was introduced to collect a batch of jobs before processing them and printing out results. • A batch system consists of three stages— • job collection, • job processing, • and printing out results. All three stages can occur concurrently.

  10. Since CPU processing and I/O processing can occur concurrently, a job that is waiting for its I/O to complete can be overlapped with a job that is using CPU. • This is now the beginning of multiprogramming, or allowing multiple programs to run concurrently.

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