Operating System meaning/definition
In simple words Operating systems are software's which help user's to interact with a machine. For a normal user a computer without operating system is just a useless machine. Operating systems are not only used in computers but it's installed in almost all user friendly machines operated by humans like mobile phones, robots etc. Now when we consider the computer systems the purpose of operating systems is not only to provide a convenient user interface but also to organize the hardware and software installed in the machine.
How operating systems work
An operating system works in the middle of software and hardware. When a user gives an instruction or command through a software its passed to the operating system. The operating system allocates memory from the RAM and gives that instruction to the CPU for executing it. Multitasking is also done in this way. Certain programs in a computer are given high, medium and low priorities and the instructions are executed according to these priorities. For example when ever explorer in your Windows operating system crashes you will press 'Alt+Ctrl+Del' for task manager and we use task manager to end the non responding program. In Windows, task manager is given a high priority and that's why it opens even if explorer is crashed.
Consider the figure, here the user gives instruction through software. Software passes instruction to operating system and OS to hardware. The return path is from hardware to OS and then from OS to software (result). For example you click on the 'X' button to close Windows media player. Then the instruction to that software is passed to Windows operating system and then to the CPU. The CPU executes it and the result you see on desktop is closing of Windows media player.
Functions & features of operating system in a computer
An operating system has lot of functions to do in a computer. Some of them are listed below:
1) Provide user interface - As said earlier without a proper user interface its difficult to manage a machine. It is possible to interact with a machine using the commands, but it's easy to learn all the commands used in an OS.
2) Input/output management - We can add additional hardware's to a computer and configure them easily with the help of an operating system. Printer, external hard disk, scanner, USB drives are some of the external devices we can connect with a computer.
3) Memory and CPU management - Operating system allocates the memory and other resources for the other programs in a computer. The memory allocation and CPU usage of each program is controlled by OS and you can check them from the 'Task Manager'.
4) Multitasking - Multitasking is another feature of operating systems (not in DOS). We can do more than one tasks at the same time in an operating system. For example you can listen to music in media player while typing a note.
5) Networking - Its easy to do networking with the help of operating systems. You can share files, folders or even hardware resources like printer through a network with the help of operating systems.
Types of operating systems
Operating systems are classified into different types they are:
1) Single user, single tasking operating system - Single user single tasking operating systems are those operating systems which can be used by a single user at a time. Also we can only do a single task at a time in such operating systems. Example of single user single tasking operating system is MS DOS. In Microsoft DOS only one program can be executed by a user at a time.
2) Single user multi tasking operating system - Single user multi tasking operating systems are those operating systems which can be used by a single user to do multiple operations/tasks at a time. Microsoft Windows is an example of such operating system. In Windows only one user can log in at a time but that user can do many tasks at a time.
3) Multi user, multi tasking - In multi user multi tasking operating systems more than one user can log in at a time and do as many tasks they want. Linux is an example of such operating system. This is the main difference between a windows and Linux operating system. In Linux there are 7 terminals, in which 6 are non graphical terminals and 1 is graphical terminal. So 7 users can use a Linux machine at a time.
4) Real time operating systems - Real time operating systems are operating systems used in real time applications like embedded systems, robots, automobile engine controllers etc. Windows CE is an example for real time operating system.
5) Chrome OS - Chrome OS is the new operating system developed by Google and it cannot be added in any of the classification listed above. It's not actually an operating system but its a web browser with advanced feature. Imagine a computer only having an internet connection and Chrome OS and that's what Google is making. In a computer with Chrome OS the data will be stored in internet and anything we do or install in an OS will be done in internet space. So its sure that Chrome OS is going to make a revolutionary change in the history of operating systems.