OPERATING SYSTEM
by sumit kumar
Features of Operating System - Concept of OS, OS DOS, Windows 98
Features of Operating System. In this article, Everything will be told about Operating System like what is What is an OS, Concept of Operating system, Types of Operating Systems EOS commands, Features of Windows 98 etc
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| Computer Operating System |
Concept of Operating System
An Operating System (OS) is a software that controls the internal activities of the computer hardware and provides user interface. All application programs need to be grogrammed in such a way that they talk with the operating system for interacting and use hardware resources.
It is the first program loaded (copied) into the computer's memory after the computer is switched on. Popular operating systems are Windows XP Windows vista, OS/2 and Unix. IBM Mainfrme computer uses MVS, VM or DOS/VSE operating system.
NOTE - One of the promary jobs of the Operating System is to provide an interface between the user and the hardware. This interface enbles a user to us hardware resources efficiently.
Operating System (OS) is primarily concerned with allocating and deallocating computer resources to one or more jobs. In fact, it can be looked upon as a cover on the hardware. Thus, an OS is an important prat of every computer system.
Operating system that support a single user at a time is a single-user operating system such as Windows XP. Some, like Linux Unix eetc. support multiple users at a time.
An operating system performs the following function:
Processor Management : The operating system assigns processors (if a computer has more than one processor ) to the different tasks that must be performed by the computer system.
Memory Management : It (OS) allocates the main memory and secondary memory to the system programs, user programs and data.
Input/Output Management : It carries out the input/Output management and co-ordinates and assigns different input and output devices.
File Management : It manages files on various storage devices and the transfer of these files from one storage device to another. It also allows all files to be easily changed and modified through the use of text editors or some other file manipulation software packages.
Schelduling : It establishes and enforces the job priority. That is, it determines and maintains the order in which jobs are to be executed in the computer system.
Timesharing : It co-ordinates and assigns compilers, assemblers, utility programs, and other softwre packages to various users working on the computer system.
Security Management : It establishes data security and integity. That is, it keps different programs and data in such a manner that they do not interfere with each other. Moreover, it also protects data from being deestroyed b y any other user.
NOTE : Some of the popular operating systems are MS-DOS, WINDOWS XP, VISTA, UNIX, LUNUX, SOLARIS and OS/2.
All operating systems can be classified into four categories.
Single User Operating System : Operating system which allows only one user to work on a computer at a time is known as single user operating system. Examples include DOS, Windows, etc.
Multiuser Operatinbg System : A Multiuser operating system allows a number of users to work to gether ona single computer. Each user will b e provided a terminal connected to a single computer. Examples include Linux, Unix, Windows 2000, etc.
Single tasking Operating System : Operating System which can execute only a single task at a time is known as single tasking operating system. eg. DOS.
Multitasking Operating System : Multitasking operating system supports execution of more than one job at a time. Most of today's operating systems such as Windows 2000, OS/2, UNIX, LINUX etc. support multitasking.
Why OS is required?
User interacts with the application programs but the application programs do not access the hardware resources directly. Hardware resources include input/output devices, primary Memory, secondary Memory (like Hard Disk, etc. ) and the microporcessor. Therefore, an aperating system is required to access and use these resources. The application programs are so created that they talk with the operating system to get access to the resources. (See Figure 1.1)
NOTE : An Operatinbg System (OS) is the first program that is loaded (copied) into the computer's main memory, when a computer is switched on. The efficiency of any operating system measured in terms of its throughput, turn around time and response time.
The two primary objectives of an operating system are:
- To enable running of Application programs.
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| program talk with an OS loaded in a computer |
- To manage the different computer resources.
:- Examples of Operating System
An overview of the different types of operating system are :
- Single-user Operating System
- Multiuser Operating System
- Single-tasking Operating System
- Multitasking Operating System
- Real-time Operating System
- Multiprogramming
- Network Operating System
- Distributed Operating System
Single-user Operating System
Operating system which allows only one user to work on a computer at a time is known as single user operating system. Examples include MS-DOS, windows etc.
Multiuser Operating System
A Multiuser operating system allows a number of users to work together on a single computer. UNIX is a multiuser operating system. It is not that all users will bump on a computer at the same time. Each user will be provided with a terminal and all such terminals will be connected to the single computer. Examples of multiuser operating systems are Linux, Unix, Windows 2000.
NOTE : Multiuser operating system running on a computer will manage the work of all users, without letting them know that they all are actually working on a single computer.
Single-tasking Operating System
Operating System which can execute a single job at a time is known as Single-tasking operating system. For example, MS-DOS is a single tasking operating system because you can open and run only one application in DOS, at one time.
Multitasking OPerating System
Multitasking operating system allows the user to perform more than one job at the same time on a computer. Most of today's operating system such as Windows, OS/2, UNIX, LINUX tc. support multitasking. For example, when you open MS-Word and Internet Explorer at the same time, the Windows operating system is doing multitasking. Thee operating system is able to keep track of where you are in each of these applications and switch from one to another without losing track.
Real Tme vs Time Sharing Operating Systems
Time Sharing System : Time Sharring is a mode of processing in which more than one user uses the CPU time. It is so named because th procssor time is shared among multiple users. Tme sharing uses multiprogramming.
NOTE : Development of time sharing operating system was motivated by the desire to provie fast response to user requests.
Thus, time sharing is a term used to describe a computer system that has a number of independent, relatively low sped, on-line, simultaneously usable terminals. Each terminal provides direct access to the CPU. In other words, time shaing refers to the allocation of computer resources in a time-dependent fashion to several users simultaneously. Main purpose of a time sharing system is to provide a large number of users direct access to the computer for problem solving.
Time sharing is accomplished by providing a separat terminal to each user. All these terminals are connected to the main computer system. Thus, a time sharing system has many terminals linked up to the same coputer at the same time. This is shown in Figure 1.2. In time sharing, the CPU time is divided among all the users on a scheduled basis.
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| Concept of a time sharing system |
Realtime System : Realtime Systems are online computer systems which provide immediate processing and also respond to user's commands immediately. They can respond to transaactions by updating the coresponding master files right away. Although the term is commonly used in reference to business application, it is most appropriately used in process contro and scientfic processing like airplane control and spacee vechicle operations.
NOTE : Realtime also refers to simulated operations that are performed in the same timeframe as a real operation.
Multiprogramming
Most medium and large computers use multiprogramming operaing systems. Multiprogramming is the nam given to the interleaved execution of two or more different and independent programs by the same computer. In multiprogramming several programs are processed by a computer simultaneously. Usually a CPU is much fastr as compared to I/O devices. While I/O devices are performing certain tasks the CPU may not be doing any task, it may be lying idle. To keep CPU busy for most of the time, it is desirable to process a number of programs concurrently. This is achieved by overlapping CPU and I/O operations when several programs are running simultaneously.
Scheduling various tasks such as Input/Output, processing etc are an important activity of an operating system (OS). As the processor is very fast compared to the speed of the Input/Output devices, the expensive processor will be kept idle during the Input/Output procedures. Hence operating systems have benn developed which can supervise the processing and manage the Input/Output and memory allocations of more than one program simultaneously.
Such OS are called multiprogramming OS. Let program A, B and C be concurrently processed by a computer . Suppose that program A processes a file and at time t, ti needs some input. The OS instructs the input device to transfer the required data. During this time the processor is free and the OS starts executing the second program B. Ehen B needs some Input or Output, if A is ready, the processor is switched back to A and if not is switched to C. The Figure 1.3 explai6ns this procedure clearly.
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| Concept of multiprogramming system |
The input data are collected in Buffers while other task is being procsed. The buffers can receive input at the speed of the input devices and release them at electronic speed to the processor. Similarly, output data are collected in output buffers which receives data at high speed and rlas them at the speeds of the output device. Such multiprogramming requires highly sophisticated OS compared to the single program OS. OS software for PCs used to be single task OS while concurrent and timesharing OS were availablee for bigger machines. Nowadays multi-user operating systems are available for PCs also.
Network Operating System (NOS)
Network Operating System (NOS) is an operating system specifically designed to support interconnection of several computers. NOS provides support for multiuser operations as well as administrative, security and network management functions. Some examples of NOSs are Novell's Netware, Microsoft's Windows NT, Artisoft's LANtastic etc.
NOTE : A network operating system has to acknowledge and respond to requests from many workstaions, managing network access, resourc allocation and sharing, data protction as well as error control. It provids for printer, file-system, database and application sharing.
Distributed Operating System
A Distributed Operating System hides the existence of multiple computers (interconnected by a network) from the user. That is, the user remains unaware of the fact that many computers are being used to process the data. These computers may be located at many places around the globe. Distributed Operating System provides single-system image to its users. Each computer in a distributed computing system processes a part of the global distributed operating system. All these computers work in close coordination with each other. Processes and system resources are managd globally, and controlled from specific locations.
NOTE : Users view the complete system as a "virtual uniprocessor" and not as a collection of machines. The distributed operating system works towards generatgion this illusion.
NOTE : Degree of autonomy of individual computers in an environment that uses network operating system is very high whereas the degree of autonomy of individual computers in an environment that uses distributed operating system is considerably low.
Input/Output Bound Programs
The programs perform very little computation but handle a hige amount of data and imformation. The commercial data procesing and educational data processing environment the input and output data in large amount but computations are very little. Therefore, such programs that utilize maximum time in I/O operations arre called I/O bound programs.
CPU Bound Programs
The program, which needs very little time for I/O operations but requires large amount of time to calculate are calleed CPU bound programs. The operating speed of CPU is much faster than that of I/O operation therefore the CPU can provide the services to several programs instead of remaining idle when one program is busy with input/out operations.
On-line Processing/Random Access Processing
On-line processing premits transaction data to be fed, under CPU control, directl into secondary on-line storage devices from the point where data originates. These data may be keyed in by the use of typewriter-like terminal, or they may be prduced b y a variety of other data collection and transaction recording devices. The access to, and retrieval of, any record in quick and direct Thus, on-line processing systems feature random amd rapid input of transactions and immediate and direct access to record contents as and when needed. A simplified concept of on-line processing is illustrated.
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| On-line processing |
Multiprocessing Operating System
Multiprocessing is simultaneous processing with two or more processors in one computer or two or more computers that are processing together. When two or more computers are used, they are tied together with a high-speed channel and share the general workload between them. In the even one fails to operate, the other takes over automatically. Some large computer and powerful minicomputers contain two or more CPUs. These CUPs operate in parallel under the integrated control of an operating system to handle one task or job.
Embedded System
The operating systems designed for being used in embedded computer system are known as embedded operating systems. They are designed to operate on small machines like PDAs with jess autonomy. They are able to operate with a limited number of resources. They are very compact and extremely efficient by design. Windows CE, Free BSD and MInix 3 are some examples of embedded operating systems.
The operating system thus contribute to the simplification of the human interaction with the computer hardware. They are responsible for linking application programs with the hardware, thus achieving an easy user access to the computers.
Dos (DISK OPERATING SYSTEM)
MS-DOS (Microsoft Disk Operating System) is an operating system supplied by Microsoft Corporation of U.S.A Latest operating system (OS) available from Microsoft corporation is Windows 2000, Windows xp and Windows7/
DOS is a disk operating system based on MS-DOS and it operates on all IBM compatible personal computers. A system file contains low-level information that DOS needs to be able to configure and use specifec hardware devices. DOS's own two system files IO.SYS and MSDOS. SYS include the essential programmes that DOS needs to ve able to communicate with any of your computer's hardware. Another system file--COMFIG.SYS---contains valuable configuration information for your computer. Most system files, however, are DEVICE DRIVERS that contain instructions that tell DOS how to mainpulate specific devices. Those fils usually have the SYS extension, such as MOUSE. SYS, RAMDRI- VE. SYS, HIMEM. SYS, etc.
NOTE : DOS is a single user single tasking operating system that can support only one user and only one task at a time.
DOS Features
The key features of DOS are given below.
Simplicity and transparency - DOS is simple and very transpared. You always know what your computer is doing.
Low hardware requirements - DOS has extremely low hardware needs. It runs on every PC. What is even better is the fact that, when compared to Windows, the same tasks can run o;n much weaker hardware.
If you are new to DOS, use DOS version 6.2. It is even possible to play audio files on a 486 or Pentium class computer.
Reason not to use DOS that is:
- Application software did not evolve.
- No javascript capable browser.
- No good PDF viewer.
Frequently Asked Question
Q - Which operating System is best for mainframe computers?
A - Choose from the list of operating systems that the manufacturer supplies. On mainframes, you do not get to choose any others.
Q - What was first operating system?
A - The first operating system used for real work was GM- NAA I/O, produced in 1956 by General Motors' Research division for its IBM 704.
Q - What are the 4 major operating system?
A - For the most part, the IT industry largely focuses on the top 5 OSs, including Apple mac OS, Microsoft Windows, Google's android OS, Lixux OS, Apple IOs.
Some Important Question :
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