Introduction to Operating System

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Introduction
An operating system (OS) is the software component of a computer system that is responsible for the management and coordination of activities and the sharing of the resources of the computer. The OS acts as a host for application programs that are run on the machine. As a host, one of the purposes of an OS is to handle the details of the operation of the hardware. This relieves application programs from having to manage these details and makes it easier to write applications. Almost all computers use an OS of some type.

OSs offer a number of services to application programs and users. Applications access these services through application programming interfaces (APIs) or system calls. By using these interfaces, the application can request a service from the OS, pass parameters, and receive the results of the operation. Users may also interact with the OS by typing commands or using a graphical user interfacDesign

Linux is a modular Unix-like OS. It derives much of its basic design from principles established in Unix during the 1970s and 1980s. Linux uses a monolithic kernel which handles process control, networking, and peripheral and file system access. The device drivers are integrated directly with the kernel. Much of Linux’s higher-level functionality is provided by seperate projects which interface with the kernel. The GNU userland is an important part of most Linux systems, providing the shell and Unix tools which carry out many basic OS tasks. On top of the kernel, these tools form a Linux system with a GUI that can be used, usually running in the X Windows System .An operating system (OS) is software that manages computer hardware and software resources and provides common services for computer programs. The operating system is an essential component of the system software in a computer system. Application programs usually require an operating system to function.Batch operating system
The users of batch operating system do not interact with the computer directly. Each user prepares his job on an off-line device like punch cards and submits it to the computer operator. To speed up processing, jobs with similar needs are batched together and run as a group. Thus, the programmers left their programs with the operator. The operator then sorts programs into batches with similar requirements.

The problems with Batch Systems are following.

Lack of interaction between the user and job.

CPU is often idle, because the speeds of the mechanical I/O devices is slower than CPU.

Difficult to provide the desired priority.

Time-sharing operating systems
Time sharing is a technique which enables many people, located at various terminals, to use a particular computer system at the same time. Time-sharing or multitasking is a logical extension of multiprogramming. Processor's time which is shared among multiple users simultaneously is termed as time-sharing. The main difference between Multiprogrammed Batch Systems and Time-Sharing Systems is that in case of Multiprogrammed batch systems, objective is to maximize processor use, whereas in Time-Sharing Systems objective is to minimize response time.

Multiple jobs are executed by the CPU by switching between them, but the switches occur so frequently. Thus, the user can receives an immediate response. For example, in a transaction processing, processor execute each user program in a short burst or quantum of computation. That is if n users are present, each user can get time quantum. When the user submits the command, the response time is in few seconds at most.Network operating System
Network Operating System runs on a server and and provides server the capability to manage data, users, groups, security, applications, and other networking functions. The primary purpose of the network operating system is to allow shared file and printer access among multiple computers in a network, typically a local area network (LAN), a private network or to other networks. Examples of network operating systems are Microsoft Windows Server 2003, Microsoft Windows Server 2008, UNIX, Linux, Mac OS X, Novell NetWare, and BSD.

The advantages of network operating systems are following.

Centralized servers are highly stable.

Security is server managed.

Upgrades to new technologies and hardwares can be easily integrated into the system.

Remote access to servers is possible from different locations and types of systems.

The disadvantages of network operating systems are following.

High cost of buying and running a server.

Dependency on a central location for most operations.
Real Time operating System
Real time system is defines as a data processing system in which the time interval required to process and respond to inputs is so small that it controls the environment. Real time processing is always on line whereas on line system need not be real time. The time taken by the system to respond to an input and display of required updated information is termed as response time. So in this method response time is very less as compared to the online processing.
Regular maintenance and updates are required.

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The operating system is the most important program that runs on a computer Every general purpose computer must has an operating system that runs other programs and applications. Operating systems performs basic tasks that are recognizing input from the keyboard sending output to the display screen keeping track of files and directories on the disk and controlling devices like disk drives and printers etc.
For large systems the operating system has even greater responsibilities and powers. It make sure that different programs and users running at the same time do not interfere with each other or operate each other. The operating system is also responsible for the security that an unauthorized users do not access the system.
All major computer platforms that are hardware and software require and sometimes include an operating system like Linux, Windows, OS-400, Aix, and z/OS windows 7,windows Vista,windows Server are all examples of operating systems.
Early computers were built to perform a series of single tasklike a calculator thing and Basic operating system features were developed in the 1950's.
There are many operating systems that were useful in their day but are no longer so, such as AmigaOS , OS/2 from IBM and Microsoft, Mac OS, the non-Unix precursor to Apple Mac OSX.
The memory management among other all other things such as multiprogramming operating system kernel must be responsible for managing the all system memory which is currently in use by programs and this ensures that a program does not interfere with memory already in use by another program. Since programs time shares and the each program must have independent access to memory and with thist the use of virtual memory addressing means that the kernel can choose what memory each program may use at any given time and allowing the operating system to use the same memory locations for multiple tasks.

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Introduction to Operating System
Abstract:
The operating system is the most important program that runs on a computer. An operating system (sometimes abbreviated as "OS") is the program that, after being initially loaded into the computer by a boot program, manages all the other programs in a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.
Introduction:
An Operating system is a program that controls the execution of application programs and acts as an interface between the user of a computer and the computer hardware. An Operating system is concerned with the allocation of resources and services, such as memory, processors, devices and information. The Operating System correspondingly includes programs to manage these resources, such as a traffic controller, a scheduler, memory management module, I/O programs, and a file system.
Operating systems provide a software platform on top of which other programs, called application programs, can run. The application programs must be written to run on top of a particular operating system. Your choice of operating system, therefore, determines to a great extent the applications you can run. For PCs, the most popular operating systems are DOS, OS/2, and Windows, but others are available, such as Linux.
We can classify Operating systems in the following terms:
• Multi-user: Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.
• Multiprocessing : Supports running a program on more than one CPU.
• Multitasking : Allows more than one program to run concurrently.
• Multithreading : Allows different parts of a single program to run concurrently.
• Real time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.

Operating systems have been evolving through the years. Following table shows the history of OS.
Generations Years devices used Devices
First 1945 – 55 - Vacuum tubes - Plug boards
Second 1955 – 1965 - Transistors - Batch system
Third 1965 – 1980 - Integrated - Circuit (IC) - Multiprogramming
Fourth Since 1980 - Large scale integration - PC

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An Operating system is software that manages computer hardware and software resources and provides common services for computer programs. The operating system is an essential component of the system software in a computer system. Application programs need an operating system to function. It is low-level software that supports computer basic functions, such as scheduling task and controlling peripherals (disk drives, printer etc.) Basically it is software that runs when you turn on your PC and it is the last software you see when you turn off your computer.
INTRODUCTION:
Operating system is a most important program that runs in a computer, every general-purpose computer must have operating system to run other programs. Operating system performs basic tasks such as recognizing input from the keyboard, sending signals to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices. On the first computers, with no operating system, every program the full hardware specification to run correctly and perform standard task, and its own drivers for peripheral devices like printers and punched paper card readers. The growing complexity of hardware and application programs made operating system a necessity for everyday use.
An operating system is the software component of a computer system that is responsible for the management and coordination of activities and the sharing of the resources of the computer. The operating system acts as a host for application programs that are run on the machine. As a host, one of the purposes of an operating system is to handle the details of the operation of the hardware. This relieves application programs from having to manage these details and makes it easier to write applications. Almost all computers use an operating system of some type. Some of the operating system used in computers is LINUX, Windows, and Macintosh etc.
In others words computer is nothing without an operating system, operating system is necessary in all type of computers without it you cannot apply anything in your computer. Operating system is only way of communication between user and computer