1. By Mr. Abdalla A. Shaame

2.  An operating system is a software component that acts as the core of a computer system.  It performs various functions and is essentially the interface that connects your computer and its supported components.  An interface between users and hardware - an environment "architecture”  Provides information protection  Gives each user a slice of the resources  Acts as a control program.

3.  Convenience ◦ Makes the computer more convenient to use  Efficiency ◦ Allows computer system resources to be used in an efficient manner  Ability to evolve ◦ Permit effective development, testing, and introduction of new system functions without interfering with service 3

4. 1: Operating Systems Overview4 The Layers Of A System Program Interface Humans User Programs O.S. Interface O.S. Hardware Interface/ Privileged Instructions Disk/Tape/Memo ry

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6.  Program development ◦ Editors and debuggers  Program execution  Access to I/O devices  Controlled access to files  System access 6

7.  Error detection and response ◦ Internal and external hardware errors  Memory error  Device failure ◦ Software errors  Arithmetic overflow  Access forbidden memory locations ◦ Operating system cannot grant request of application  Accounting ◦ Collect usage statistics ◦ Monitor performance ◦ Used to anticipate future enhancements ◦ Used for billing purposes 7

8.  Responsible for managing resources  Functions same way as ordinary computer software ◦ It is program that is executed  Operating system give up control of the processor 8

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10.  Portion of operating system that is in main memory  Contains most frequently used functions  Also called the nucleus 10