Introduction of Operating System :

Operating System : –

An operating system is a program that manages the computer hardware. It is an important part of the computer system. It provides a basis for application programs and act as an interface between the computer user and the hardware. The operating system control and coordinates the use of hardware among various user. Operating system is the most basis program within the computer system. In other word we can say that an operating system is a communication link between the user and the computer system and help the user to run the application program.

Structure of Operating System :

structure of operating system

What operating system does ?

An operating system performs the following task such as.

• Controlling and allocating memory.
• Prioritizing system requests.
• Controlling input and output devices.
• Managing file system.

Operating System Goals :

Different objectives of Operating System are as follows.

1: Convenience :  The primary objective of operating system is convenience for user. Operating system executes user programs and makes it easy to solve user problem. They also make computer system convenient to use.

2: Efficiency :  A secondary objective is the efficient operation of a computer system. It is particularly important for large shared multi user system. Operating system can solve this goal. An operating system provides the facility to use the computer hardware in an efficient manner.

3: Ability to Evolve :  Operating system allows effective development testing and introduction of new system functions without interfering with the service.

Computer System Components : –

1. Hardware : –  The machines in the computer system are called Hardware In the more precise way we can define hardware as the electronic and mechanical components of a computer system. In fact these are the physical components and can be touched, handled or seen physically.
   e.g. input unit, CPU, secondary storage and output unit.

2. Operating system : –  Controls and coordinates the use of the hardware among the various application programs for the various users. It includes process management routines, Memory management routines, I/O, and file management routines.

3. Application programs : –  Define the ways in which the system resources are used to solve the computing problems of the users (Compiler, Database System, Video games, Business programs).

4. User : –  The user includes people, machine, and so on.

KERNEL :

The kernel provides the most basic interface between the computer itself and the rest of the operating system. The kernel is responsible for the management of the central processor. The kernel includes the dispatcher to allocate the central processor to determine the cause of an interrupt and initiate its processing, and some provision for communication among the various system and user tasks currently active in the system.

Main function of kernel :

Kernel is the core of an operating system; the main functions of kernel are as follows:

• It provides a mechanism for creation and deletion of process.
• It provides CPU scheduling memory management and device management for these processes.
• It provides synchronization tools so that the processes can synchronize their action.
• It provides communication tools so that processes can communicate with each other.
• The kernel based design is often used to design operating system.
• The kernel provides an environment to build an operating system in which the designer has considerable flexibility.

Resident Monitor :

In resident monitor, we have provided a separate part for operating system and other remains for user space. User cannot interfere in the OS part. For this we use a fence address which separates the OS and the user part. A part of OS always reside in main memory, called as monitor. In resident monitor entire OS cannot be loaded. In this we have to ways for allocating the memory, First one is software and other one is hardware. In software, first of all we CPU compare the address with fence address, if fence address is smaller than the process address than CPU will allocate the memory to that process and if fence address is less than the process address than CPU will generate a TRAP (error or interrupt).