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Basically the operating system is a software that manages the computer hardware. It acts as an intermediary between the user of a computer and computer hardware.
The purpose of an operating system is to provide an environment in which a user can execute programs in a convenient and efficient manner.
An operating system is concerned with the allocation of resources and services, such as memory, processors, devices, and information. The operating system correspondingly includes programs to manage these resources, such as a traffic controller, a scheduler, a memory management module, I/O programs, and a file system.
Functions of Operating System:
Convenience: An OS makes a computer more convenient to use.
Efficiency: An OS allows the computer system resources to be used in an efficient manner.
Ability to Evolve: An OS should be constructed in such a way as to permit the effective development, testing, and introduction of new system functions at the same time without interfering with service.
The operating system is a set of special programs that run on a computer system that allows it to work properly. It performs basic tasks such as recognizing input from the keyboard, keeping track of files and directories on the disk, sending output to the display screen, and controlling peripheral devices. OS is designed to serve two basic purposes:
It controls the allocation and use of the computing System’s resources among the various user and tasks.
It provides an interface between the computer hardware and the programmer that simplifies and makes feasible for coding, creation, debugging of application programs.
The Operating system must support the following tasks. The tasks are:
Provides the facilities to create, modification of programs, and data files using an editor.
Access to the compiler for translating the user program from high-level language to machine language.
Provide a loader program to move the compiled program code to the computer’s memory for execution.
Provide routines that handle the details of I/O programming.
I/O System Management
The module that keeps track of the status of devices is called the I/O traffic controller. Each I/O device has a device handler that resides in a separate process associated with that device. The I/O subsystem consists of
A memory Management component that includes buffering caching and spooling.
A general device driver interface.
Drivers for specific hardware devices.
Assembler
The input to an assembler is an assembly language program.
The output is an object program plus information that enables the loader to prepare the object program for execution.
At one time, the computer programmer had at his disposal a basic machine that interpreted, through hardware, certain fundamental instructions.
He would program this computer by writing a series of ones and Zeros (Machine language), place them into the memory of the machine.
Compiler
The High-level languages- examples are FORTRAN, COBOL, ALGOL, and PL/I are processed by compilers and interpreters.
A compiler is a program that accepts a source program in a “high-level language “and produces a corresponding object program.
An interpreter is a program that appears to execute a source program as if it was machine language.
The same name (FORTRAN, COBOL, etc.) is often used to designate both a compiler and its associated language.
Loader
A Loader is a routine that loads an object program and prepares it for execution.
There are various loading schemes: absolute, relocating, and direct-linking. In general, the loader must load, relocate, and link the object program.
The loader is a program that places programs into memory and prepares them for execution.
In a simple loading scheme, the assembler outputs the machine language translation of a program on a secondary device and a loader places it in the core.
The loader places into memory the machine language version of the user’s program and transfers control to it.
Since the loader program is much smaller than the assembler, those make more core available to the user’s program.