Operating system is considered to be the heart of computer. All the software’s resides in the operating system that manages hardware resources and provides services to the computer programs. All the application programs require operating system to function. Different types of Operating systems have been developed and are being categorized according to use. The Graphical User Interface operating system consists of graphics and icons and is being navigated with the use of mouse. Example of GUI OS are:- Windows 98, Windows CE, System 7.x. The multi user operating system allows the multiple users to use one computer resources simultaneously or at different times. Example of multi-user OS are:- Linux, Unix, Windows 2000. The multiprocessing operating systems are those which are capable to utilize and support more than one processor of the computer. Example:- Unix, Windows 2000, Linux. The multitasking operating system allows several software processes to run at one time. Example:- Unix, Windows 2000. The multithreading operating system allows different parts of one software program to run concurrently by dividing the task of one software into multiple threads. Example:-Windows 2000, Linux, Unix. The Real time Operating system (RTOS) is being designed to control scientific instruments, machinery and industrial systems. The RTOS support very less user interface and has no end-user capabilities.
Operating system acts as bridge between the software applications and the hardware of the computer. Operating system provides the resources to software applications like central processing unit to do the processing for software processes, memory unit to store the data or to fetch the data, Logical unit to perform logical functions like addition, division, subtraction, modulus etc. according to the requirement. It also sets the rules or the order in which the software can access the hardware, so that no two software applications demand for the same resources at one time. This helps to avoid the deadlock situation which makes the computer system hang and no functionality is being performed.
When the computer is being turned on then certain set of instructions runs which is present in the computer’s Read Only Memory (ROM). These set of instructions verifies the system hardware functionality. The other name for this process is power-on self-test (POST) which checks the CPU, basic input output system for errors and stores the result in the memory. After the POST is successful the software applications are being loaded and the operations are performed accordingly. The start-up of the computer requires some loader to load the operating system into memory and this work is done by the bootstrap loader which consists of the small program.