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Operating Operating SystemsSystems

The general objectives of The general objectives of this decisionthis decision

explain the concepts and the explain the concepts and the importance of operating systems and importance of operating systems and development and how they work.development and how they work.

explain the types of operating systems ..explain the types of operating systems .. Explain the concept and how to Explain the concept and how to

Processes ManagementProcesses Management clarify the basic algorithms for the clarify the basic algorithms for the

management of various computer sourcesmanagement of various computer sources explain the concept of memory and how explain the concept of memory and how

to manage them and the concept of to manage them and the concept of virtual memory.virtual memory.

IntroductionIntroduction What is an Operating System?What is an Operating System? Mainframe SystemsMainframe Systems Desktop SystemsDesktop Systems Multiprocessor SystemsMultiprocessor Systems Distributed Systems Distributed Systems Clustered SystemClustered System Real -Time SystemsReal -Time Systems

Computer System Computer System ComponentsComponents

1.1. HardwareHardware – provides basic computing – provides basic computing resources (CPU, memory, I/O devices).resources (CPU, memory, I/O devices).

2.2. Operating systemOperating system – controls and – controls and coordinates the use of the hardware among coordinates the use of the hardware among the various application programs for the the various application programs for the various users.various users.

3.3. Applications programsApplications programs – define the – define the ways in which the system resources are ways in which the system resources are used to solve the computing problems of used to solve the computing problems of the users (compilers, database systems, the users (compilers, database systems, video games, business programs).video games, business programs).

4.4. UsersUsers (people, machines, other (people, machines, other computers). computers).

Abstract View of SystemAbstract View of System ComponentsComponents

What is an Operating System?

A program that acts as an A program that acts as an intermediary between a user of a intermediary between a user of a computer and the computer computer and the computer hardware.hardware.

Execute user programs and Execute user programs and make solving user problems make solving user problems easier.easier.

Resource allocator – manages all Resource allocator – manages all resource and decides between resource and decides between confecting requests for efficient confecting requests for efficient and fair resource useand fair resource use

What is an Operating System?

Control program – controls the Control program – controls the execution of user programs and execution of user programs and operations of I/O devices .operations of I/O devices .

Kernel – the one program Kernel – the one program running at all times (all else running at all times (all else being application programs).being application programs).

The evolution of The evolution of Operating System

Simple Batch SystemSimple Batch System

Systems are operating in this modle Systems are operating in this modle has the following properties :-has the following properties :-

1- carrying out a series of tasks one 1- carrying out a series of tasks one after the otherafter the other

2- A operator player of his experience 2- A operator player of his experience and operation of the systemand operation of the system

3- there is an monitor in memory to 3- there is an monitor in memory to load the task an transfer control to load the task an transfer control to the observer againthe observer again

Memory Layout for a Simple Memory Layout for a Simple Batch SystemBatch System

Multi programmed Batch Multi programmed Batch SystemsSystems

Several jobs are kept in main memory at the same time, and the CPU is multiplexed among them.

OS Features Needed for OS Features Needed for Multi programmingMulti programming

I/O routine supplied by the system.I/O routine supplied by the system. Memory management – the system Memory management – the system

must allocate the memory to must allocate the memory to several jobs.several jobs.

CPU scheduling – the system must CPU scheduling – the system must choose among several jobs ready choose among several jobs ready to run.to run.

Allocation of devices.Allocation of devices.

Time-Sharing Systems–Time-Sharing Systems–Interactive Computing Interactive Computing

The CPU is multiplexed among The CPU is multiplexed among several jobs that are kept in several jobs that are kept in memory and on disk (the CPU is memory and on disk (the CPU is allocated to a job only if the job allocated to a job only if the job is in memory).is in memory).

A job swapped in and out of A job swapped in and out of memory to the disk.memory to the disk.

On-line system must be available On-line system must be available for users to access data and code.for users to access data and code.

Desktop SystemsDesktop Systems computer system dedicated to a computer system dedicated to a

single user.single user. User convenience and User convenience and

responsiveness.responsiveness. Do not need advanced CPU Do not need advanced CPU

employment of protection employment of protection features.features.

May run several different types May run several different types of operating systems (Windows, of operating systems (Windows, MacOS, UNIX, Linux)MacOS, UNIX, Linux)

Parallel SystemsParallel Systems Multiprocessor systems with more Multiprocessor systems with more

than on CPU in close communication.than on CPU in close communication. processors share memory and a processors share memory and a

clock; communication usually takes clock; communication usually takes place through the shared memory.place through the shared memory.

Advantages of parallel systemAdvantages of parallel system: : Increased Increased throughputthroughput EconomicalEconomical Increased reliabilityIncreased reliability

Parallel Systems (Cont.)Parallel Systems (Cont.)

Symmetric multiprocessing :-Symmetric multiprocessing :- Each processor runs and identical Each processor runs and identical

copy of the operating system.copy of the operating system. Many processes can run at once Many processes can run at once

without performance deterioration.without performance deterioration. Asymmetric multiprocessing :-Asymmetric multiprocessing :-

Each processor is assigned a Each processor is assigned a specific taskspecific task

More common in extremely large More common in extremely large systemssystems

Distributed SystemsDistributed Systems

Distribute the computation among Distribute the computation among several physical processors.several physical processors.

each processor has its own local each processor has its own local memory; processors communicate memory; processors communicate with one another through various with one another through various communications lines, such as communications lines, such as high-speed buses or telephone high-speed buses or telephone lines.lines.

Advantages of distributed Advantages of distributed systems :-systems :-.. Resources Sharing Resources Sharing Computation speed up – load sharing Computation speed up – load sharing ReliabilityReliability Requires networking infrastructureRequires networking infrastructure

Real-Time SystemsReal-Time Systems

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