CBSE Notes for Class 9 Foundation of Information Technology – Operating System
Operating system is the most important program that is required by the computer to communicate with the user and other hardware devices (peripherals) attached to it. An operating system is also a platform that decides the types of applications that can be run on a computer.
An operating system is a system software which acts as an interface between the user and the computer.
NEED FOR OPERATING SYSTEM
- Computer has many resources like processor, files, memory, devices etc. Operating system acts as a resource manager.
- Operating system provides an interface between the user and the machine.
- Operating system boots the computer.
- Operating system provides a platform for executing various application programs.
- Operating system secures the user programs.
- Operating system helps in performing input/output operations.
- When one process requires to communicate with another process, operating system makes this communication possible.
- Errors like printer offline, failed memory allocation are all detected by operating system. For many errors, operating system itself takes appropriate action.
OPERATING SYSTEM AS RESOURCE MANAGER
Files, devices, peripherals, CPU, memory etc. are some of the major resources of a computer. A computer has various processes running simultaneously at any point of time. These processes require different resources at different times and for different durations. The major work of operating system as a resource manager are:
- To keep track of available resources i.e., to keep a note of which resource is free.
- To decide which process has to be allotted a resource, when and for how long. For taking this decision, it takes help of some algorithms like First come First serve, Shortest Duration First, Round Robin etc.
- To allocate the resource to the process.
- To deallocate the resource after the allotted time is over.
FUNCTIONS OF OPERATING SYSTEM
Fet us now see in detail the functions of operating system.
Processor is the most important resource of a computer. When many processes are running on a computer and each requires the processor, the operating system decides which process has to be allocated to the processor, when and for how long. It allocates the processor and after the allotted time slot, it deallocates the processor.
The next most sought after resource is the memory. Operating system while acting as the memory manager decides which memory, how much memory and for how long the memory is to be allocated to a process. It then deallocates the memory too.
The file manager allocates files and directories to processes. The files may be the hard disk or external storage devices. It also helps the computer and the user to read/write data from/to the storage device.
There are several devices attached to the computer such as keyboard, mouse, speakers, microphone etc. Each device has driver software which is launched by the operating system for the device to work. Most of the operating system have built-in drivers for the commonly used devices.
USER-OPERATING SYSTEM INTERFACE
The user can interact with operating system in two ways:
Command-Line Interface or Command Interpreter
It allows user to enter commands for any operation to be performed. For example, UNIX, MS-DOS.
Graphical User Interface (GUI)
Another way of interacting with the operating system is through GUI. It is a user-friendly interface and so the most preferred and liked operating system. The user does not have to enter any command. The commands appear on the screen in form of menu or as icons (small pictorial representation). The user uses a pointing device like mouse or light pen etc. to position the pointer on the icon on the screen. Clicking the mouse on the required position triggers the execution of the command or opens the file/folder. The best example of GUI based operating system is MS-Windows, Macintosh.
GUI is an interface between user and computer which uses menus, icons, tabs and buttons and all these can be selected using a pointing device like mouse.
Advantages of GUI
- It is easy to operate and very user-friendly.
- Use of icons and tabs etc. makes it more attractive.
- No prior knowledge of syntax of commands is required.
- Multitasking is possible while using GUI. This means that more than one application can be run simultaneously.
- The convenience of the use of GUI has resulted in development of many user friendly softwares like Desktop Publishing. .
Limitation of GUI
Inspite of the attractive and convenient uses of GUI, people prefer Command Line Interface because it is very powerful and gives more liberty and more advanced features.
Command Line Interface (CLI)
MS-DOS, UNIX, LINUX are some of the most commonly used Command Line Interface. Here unlike GUI, mouse is not used. Instead commands are typed using keyboard. Commands are typed next to a prompt. For example, the address line of a web browser is a command line.
C:\> in MS-DOS
Advantage of CLI
Command Line Interface is preferred over Graphical User Interface even today as it gives the user more power to exploit the features of the computer and also the operating system.
Limitation of CLI
The user needs to learn the syntax of numerous commands in order to use CLI.
Real Time Operating System
Response time is the time taken by a system to react to a given input. In a Real Time Operating System (RTOS), the response time is very critical and is fixed. In case of any event, the system has to respond within a fixed duration of the time or else the system might collapse. So we can say that RTOS is time-driven.
Usually in a RTOS, the output of one unit acts as an input for another unit. So delay in receiving output from a unit delays the supply of input to the next unit. The second unit does not respond to the delayed input and so does not give any output for which the third unit might be waiting. So the whole system crashes.
The best examples of RTOS are airbags in a car, fire alarm system, aircraft control system.
Generally, RTOS are embedded systems meaning that they are a part or a unit of a larger system. For example, temperature control system in ACs and refrigerators, digital watches, MP3 players, in mobile phones etc. Some of the widely used RTOS are LINUX, Windows CE, RT LINUS, OSE, QNX etc.
Differences between Real Time Operating System and General Purpose Operating System
|Real Time Operating System
|General Purpose Operating System
|1. It has deterministic time behaviour i.e. the operating system consumes only an expected amount of time.
|1. The time consumed by a process is not fixed.
|2. It is time-driven system.
|2. It is process-driven system.
|3. These are generally embedded systems e.g., controllers in washing machines, ACs.
|3. These are not embedded systems e.g., personel computers, desktops.
Distributed Operating System
A distributed operating system is a software that is designed to work in an environment where a number of computers are connected in a network. So the operating system software is not stored on a single computer but its different parts are stored on different
computers. But the user does not feel the distribution. He/ She gets an impression that his/her computer is working as an independent system.
So in a distributed operating system there are several servers that share memory and tasks. This results in an efficient and powerful environment for computing.
The operating system keeps a check on the availability of different processors and makes sure that none of them is overloaded. The operating system distributes the tasks evenly between different parts of the computer and thus increases the efficiency of the system.
COMMONLY USED OPERATING SYSTEM
It is a multiuser computer operating system developed by AT&T at Bell Labs. It is written in C language and operating system is portable. It was first developed in 1960s and new features have been added to it ever since.
UNIX operating system is:
- Multiuser (many terminals are attached so that many users can use the machine simultaneously).
- Multitasking (more than one process can be run at a time).
- Portable i.e., can be shifted from one computer to another without any change.
- The directory structure is hierarchical.
- Supports CLI as well as GUI.
- UNIX has three-layered structure:
- Kernel: It schedules the tasks as in a multiuser system or a multitasking system. There are various tasks requesting the access of resources such as processor. It is also responsible for the security of the system.
- Shell: It is an interface between the user and the Kernel.
It interprets the user’s commands and executes them.
- Utilities: UNIX has numerous utility programs and new utility programs can be made from the existing ones. *•
UNIX has many tools which can be used in software development at various stages i.e., program editing for maintenance of software. Most of the computers from minicomputers to mainframes use UNIX as operating system.
LINUX as an operating system is fast becoming popular. Although it has not touched the popularity of Windows operating system but still is providing a high competition to Windows operating system. This can be said because of the following features of LINUX:
- It is a multiuser operating system which can be run in single mode also.
- It can run on many computer models unlike Windows which can run only on Intel machines.
- It comes for free. Windows is an expensive operating system but LINUX can be downloaded for free.
- The source code of LINUX is open and accessible to all. So anyone can make changes in it according to one’s own need. This is the reason behind new features being added to LINUX every now and then.
- The security system of LINUX is very strong. It is not easily infected by Viruses.
- In case a user detects a threat, LINUX being an open source, the whole community using LINUX starts working on the threat to find its solution, so it gets rectified faster.
It is a Unix operating system developed by SUN Microsystems. But now it is commonly known as Oracle Solaris after Oracle took over SUN in January 2010. It is basically used on SUN’s hardware—SPARC.
The main features of Solaris are:
- It is programmed in C language.
- It belongs to the UNIX operating system cluster.
- When executed on SPARC machine, its performance is excellent.
- Solaris lacks good GUI as compared to Windows and MAC operating system.
- Solaris is best suited with SPARC so buying Solaris means buying the specific hardware too. Here LINUX has an upperhand as it is a free software and has no restrictions of hardware.
BOSS-Bharat Operating System Solutions
India’s own personal computer operating system developed by India’s own software industry is BOSS LINUX or BOSS GNU/LINUX. Released for the first time in January 2007, its latest version was launched in February 2011. BOSS is a free open source software (OSS) and is developed by a government department named National Resource Centre for Free/Open Source Software (NRCFOSS) under C-DAC (Centre for Development of Advanced Computing). It is available in 18 Indian languages and the Indian Government aims its implementation at national level.
It being multilingual is used by all government organisations and offices. Moreover BOSS being a free open source software, is favourable cost-wise and easy to install and maintain. It is also available with the latest updates from the BOSS user’s community. Since this operating system has the government’s support, chances of the remote areas of our country getting access to BOSS are stronger. This would reduce the digital gap between the urban and the rural India. BOSS can be run on Intel and AMD x 86/x 86-64 machines.
Windows Operating System
Till 1985 Command Line Interface like MS-DOS was used. In 1985 Microsoft developed and launched a Graphical User Interface based operating system called Windows. It gained instant and huge popularity and at present it is the most popular and widely used operating
system for personal computers. This is due to the following features:
- Programmed in C++ and Assembly language.
- It is a closed source software.
- Latest version released is Windows 8 which can be used on TABs also.
- Supports many languages.
- Windows versions like Windows NT can be used on computers connected in a network.
- It is because of its popularity, various worms, trojans and viruses are specially written by people with malicious motives against Windows. So regular updates are made available by Microsoft for the Windows users. The updates can be downloaded by the user online.
MOBILE OPERATING SYSTEMS
Mobile phones have become a necessity of our lives. New types of phones are being launched everyday with increased processor speed, new added features, compact size, light in weight, facility of attaching more peripherals, Bluetooth, WiFi, GPS navigation, improved camera, touchscreen etc.
Every mobile phone, TAB (tablet), PDA (Personal Digital Assistant) need an operating system. These devices being mobile, their operating system are referred to as mobile operating systems.
Some of the commonly used mobile operating systems are discussed here:
It is a free and open source software developed by Google along with Open Handset Alliance.
- It is programmed in C, C++ and Java.
- It belongs to the family of LINUX operating system.
- Released on September 23,2008 initially, its latest version was release on November 13, 2012 called Android 4.2 Jelly Beans. Each new release is named after a dessert in alphabetical order. Cup cake and Domit are two of the earlier released version.
- The major users of Android at present are HTC and Samsung.
- Working on an Android phone is more or less like using a computer. The homescreen has several icons which can be selected by touch. Several other types of touch inputs like tapping, swiping, pinching etc. are also available.
Symbian is an operating system designed by Symbian Foundation and now maintained by Accenture.
- It is an open source platform.
- Before Android captured market in 2010, Symbian was the most popular smartphone operating system.
- All Nokia devices and Sony Ericsson phones use Symbian.
- It is programmed in C++.
- The latest phone with the latest version of Symbian is Nokia 808 Pure View.
- Since Symbian is slowly loosing popularity so Nokia is switching from Symbian to Windows operating system for phones named Lumia 800 and Lumia 710.
Comparision of Android with Symbian
|1. Modifications in the phone can be made.
|1. Nokia does not allow any modification with the phone.
|2. If you want to go for a new version of Android, you do not have to change your phone.
|2. For using a new version of Symbian, you most of time need to buy a new Nokia phone.
|3. New phone features can be downloaded and used as default applications. The older versions can be removed so that phone’s memory does not get wasted.
|3. Original setting cannot be easily changed. If new applications are downloaded, they cannot be used as default setting but as additional features. So the original version still stays in the memory thus unnecessarily using the memory.
Other Mobile Operating Systems
Various other operating systems for mobile phones are available in the market although not as popular as Android. A few are mentioned below:
- bada for Samsung Electronics (closed source)
- BlackBerry OS from RIM (closed source)
- iOS from Apple Inc. (closed source) used on iPhone, iPod, iPad etc.
- Windows from Microsoft (closed source)