1. المحاضرة الاولى Operating Systems

2. The general objectives of this decision explain the concepts and the importance of operating systems and development and how they work. explain the concepts and the importance of operating systems and development and how they work. explain the types of operating systems.. explain the types of operating systems.. Explain the concept and how to Processes Management Explain the concept and how to Processes Management clarify the basic algorithms for the management of various computer sources clarify the basic algorithms for the management of various computer sources explain the concept of memory and how to manage them and the concept of virtual memory. explain the concept of memory and how to manage them and the concept of virtual memory.

3. Introduction What is an Operating System? Mainframe Systems Desktop Systems Multiprocessor Systems Distributed Systems Clustered System Real -Time Systems

4. Computer System Components 1.Hardware – provides basic computing resources (CPU, memory, I/O devices). 2.Operating system – controls and coordinates the use of the hardware among the various application programs for the various users. 3.Applications programs – define the ways in which the system resources are used to solve the computing problems of the users (compilers, database systems, video games, business programs). 4.Users (people, machines, other computers).

5. Abstract View of System Components

6. What is an Operating System? A program that acts as an intermediary between a user of a computer and the computer hardware. A program that acts as an intermediary between a user of a computer and the computer hardware. Execute user programs and make solving user problems easier. Execute user programs and make solving user problems easier. Resource allocator – manages all resource and decides between confecting requests for efficient and fair resource use Resource allocator – manages all resource and decides between confecting requests for efficient and fair resource use

7. What is an Operating System? Control program – controls the execution of user programs and operations of I/O devices. Control program – controls the execution of user programs and operations of I/O devices. Kernel – the one program running at all times (all else being application programs). Kernel – the one program running at all times (all else being application programs).

8. The evolution of The evolution of Operating System

9. Simple Batch System Systems are operating in this modle has the following properties :- 1- carrying out a series of tasks one after the other 2- A operator player of his experience and operation of the system 3- there is an monitor in memory to load the task an transfer control to the observer again

10. Memory Layout for a Simple Batch System

11. Multi programmed Batch Systems Several jobs are kept in main memory at the same time, and the CPU is multiplexed among them.

12. OS Features Needed for Multi programming I/O routine supplied by the system. I/O routine supplied by the system. Memory management – the system must allocate the memory to several jobs. Memory management – the system must allocate the memory to several jobs. CPU scheduling – the system must choose among several jobs ready to run. CPU scheduling – the system must choose among several jobs ready to run. Allocation of devices. Allocation of devices.

13. Time-Sharing Systems–Interactive Computing The CPU is multiplexed among several jobs that are kept in memory and on disk (the CPU is allocated to a job only if the job is in memory). The CPU is multiplexed among several jobs that are kept in memory and on disk (the CPU is allocated to a job only if the job is in memory). A job swapped in and out of memory to the disk. A job swapped in and out of memory to the disk. On-line system must be available for users to access data and code. On-line system must be available for users to access data and code.

14. Desktop Systems computer system dedicated to a single user. computer system dedicated to a single user. User convenience and responsiveness. User convenience and responsiveness. Do not need advanced CPU employment of protection features. Do not need advanced CPU employment of protection features. May run several different types of operating systems (Windows, MacOS, UNIX, Linux) May run several different types of operating systems (Windows, MacOS, UNIX, Linux)

15. Parallel Systems Multiprocessor systems with more than on CPU in close communication. Multiprocessor systems with more than on CPU in close communication. processors share memory and a clock; communication usually takes place through the shared memory. processors share memory and a clock; communication usually takes place through the shared memory. Advantages of parallel system: Advantages of parallel system: Increased throughput Increased throughput Economical Economical Increased reliability Increased reliability

16. Parallel Systems (Cont.) Symmetric multiprocessing :- Symmetric multiprocessing :- Each processor runs and identical copy of the operating system. Each processor runs and identical copy of the operating system. Many processes can run at once without performance deterioration. Many processes can run at once without performance deterioration. Asymmetric multiprocessing :- Asymmetric multiprocessing :- Each processor is assigned a specific task Each processor is assigned a specific task More common in extremely large systems More common in extremely large systems

17. Distributed Systems Distribute the computation among several physical processors. e each processor has its own local memory; processors communicate with one another through various communications lines, such as high-speed buses or telephone lines. Advantages of distributed systems :-. Resources Sharing Computation speed up – load sharing Reliability Requires networking infrastructure

18. Real-Time Systems Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems.