Presentation On Os.pptx

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Introduction of Operating system Meaning of Operating system Objective of Operating system Generation of Operating system Types of Operating system Classification of Operating system

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The 1960’s definition of an Operating system is “the software that controls the hardware.” However, today, due to microcode we need a better definition. The most important program that runs on a computer. Every general-purpose computer must have an Operating system to run other programs. For large systems, the Operating system has even greater responsibilites and power. It is like a traffic cop.

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Some examples of operating system are LINUX , UNIX, Ms-Windows, MS-DOS, VMS, MVS, VM ETC.

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An Operating system (OS) is an interface between hardware and user which is responsible for the management and coordination of activities and that acts as a host for computing applications run on the machine. An Operating system (OS) is software, consisting of programs and data, that runs on computer hardware resources and provide common services for efficient execution of various applications software.

The two main objectives of OPERATING SYSTEM is: Making a computer system user friendly:A computer system consist of one or more processors, main memory and many type of I/O devices such as disks, tapes, terminals, network interface, etc. Writing programs for using these hardware resources correctly and efficiently is an extremely difficult job. The gradually evolved solution to handle this problem is to put a layer of software on top of the bare hardware, to manage all the parts of system

And present the user with an interface or virtual machine that is easier to program and use. This layer of software is called OPERATING SYSTEM.  Managing there sources of a computer system:The second most important job of Operating system is to manage the various resources of the computer system. This involves performing such tasks as keeping track of ‘who is using which resources,’ granting resources requests, accounting for resources usage, and mediating conflicting requests from different program and users.

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The 1940’s - FIRST GENERATION The 1950’ - SECOND GENERATION The 1960’s - THIRD GENERATION Onward 1960’s - FOURTH GENERATION

There are two type of Operating System are as follows: Single user OPERATING SYSTEM (for example MS-DOS)  Multi user OPERATING SYSTEM (for example LINUX, WINDOWS, etc.)

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MS-DOS MICROSOFT WINDOWS 3.1 AND 3.11 MICROSOFT WINDOWS 98 WINDOWS 98 SE MICROSOFT WINDOWS 2000 WINDOWS 7 MAC 059 MICROSOFT WINDOWS XP MICROSOFT WINDOWS ME

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Multi user OPERATING SYSTEM Multi tasking OPERATING SYSTEM Multiprocessing OPERATING SYSTEM Multithreading OPERATING SYSTEM Real time OPERATING SYSTEM Disturbed OPERATING SYSTEM Embedded OPERATING SYSTEM

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Multi user Operating system allows concurrent access by multiple users of computers. Time sharing systems are most batch processing systems for mainframe computers are multi users system. An example is LINUX server where multiple remote users have access to the shell prompt at the same time.

Multi programming system are designed to maximize CPU usage. In fact, depending on CPU utilization during the course of processing, jobs are broadly classified into following two types: CPU-BOUND JOBS – These jobs mostly perform numerical calculation, with little I/O operations. They are so called because they heavily utilized the CPU during the course of their processing. Programs used for scientific and engineering computations usually fall in this category of jobs.  I/O -BOUND JOBS – These jobs normally input vast amount of data, perform very little computation, and output large amount of info.

These is because during the course of their processing, their CPU utilization is very low and most of the time, they perform I/O operations. Programs used for commercial data processing applications usually, fall in this category of this jobs. Requirements of multi user system Multi user systems have better throughput then uniprogramming system because the CPU idle time is drastically reduce. However, Multi user system are fairly sophisticated because they require the following additional hardware and software features.

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Large memory Memory protection Job status preservation Proper job mix CPU scheduling

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Multitasking allows more than one program to run concurrently. Multitasking is a method by which multiple tasks, also known as processes, share common processing resources such as a CPU. In multitasking, only one CPU is involved, but it switches from one program to another so quickly that it gives the appearance of executing all the programs at the same time.

Multitasking solves the problem by scheduling which task may be the one running at any time, and when another waiting task gets a turn. The act of reassigning a CPU from one task to another one os called a CONTEXT SWITCH. When context switches occur frequently enough the illusion of parallelism is achived. Even on computers with more than one CPU (called multiprocessor machines), multitasking allows many more task to be run than there are CPUs.

Diffrence between multi user and multi tasking:Difference between Multi user and Multi tasking is the concurrent execution of multiple jobs (of same or different users) in a Multi user system, while Multitasking is the concurrent execution of multiple jobs (often referred to as task of same user) in a singleuser system.

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Multi processing, in a general , refers to the utilization of multiple CPUs in a single computer system. Multi processing operating systems enable several programs to run concurrently. Linux is one of the most widely used Multi processing systems, but there are many others, including Os/2 for high – end PCs.

Operating system must allocate resources to competing processes in a reasonable manner.  It is also called as Parallel Processing. Multi processing systems are basically of two types namely: Tightly and loosely coupled Multiprocessing systems.  Loosely coupled Multiprocessing systems. Advantages of Multi processing OS: Better performance  Better reliability 

Limitations of Multiprocessing: Require very sophisticated Operating system.  Such OS is complex and time taking job.  This are expensive to procure and maintain.

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Multi threading allows different parts of a single program to run concurrently. It is the ability of an Operating system to execute different parts of a program called Threads, simultaneously. Multi threading is generally done in java programming. Threads are popular way to improve applications performance.

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In traditional Operating systems, the basic unit of CPU utilization is a process. Each process has its own program counter. On the other hand, in Operating system, with threads facility, the basic unit of CPU utilization is thread. Each thread of a process has its own program counter.

Difference between Multi user and Multi processing:

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Multi programming is interleaved execution of two or more processes by a single-CPU computer system. On the other hand, Multi processing is the simultaneous execution of two or more processes by a computer system having more than one CPU.