The software are the program that govern the operation of a computer system and make the hardware run. Software is not touchable. Depending upon the various use of software, it is mainly classified into the following types:
1) System Software
2) Service Software
3) Application Software
1) SYSTEM SOFTWARE :
It is a collection of master programs designed to operate the computer and control it's activities. The system software is either provided by manufacturer or independent software developers. Development of system software is called system's programming. The most important system which governs all the activities of the computer. Examples of operating system are : MS-DOS, IBM PC-DOS, APPLE-DOS, UNIX, XENIX, LINUX, Windows 9x etc.
2) SERVICE SOFTWARE :
Service software are those software which provides various services to computer user in order to program the computer. They are used to convert the program instructions of high level language to their equivalent machine language form.
Types of system software.
i) INTERPRETERS :
There are certain language utilities which are not compiler based, such as source programs are not stored. The instructions of the source program are taken one by one and immediately convert into machine language and executed instantly. But the execution time of the program increases considerably, it display errors stepwise.
ii) COMPILERS :
Compilers can be loaded into the internal memory and work when required by the user. They are also used to convert HLL instruction into machine language and object program is generated. Each HLL has it's own compiler, like Cobol Compiler, Fortran Compiler etc. It takes a lot of time as the complete source code is generated, but execution speed of the program increase tremendously. It displays all errors at a time.
HLL program ---------> Language ----------->Machine Code
(Source Code) (Compiler) (Object Program)
iii) ASSEMBLER :
To execute an assembly language program, first it should be translated into it's equivalent machine language program. The translator which does this is known as Assembler.
iv) EDITOR :
Editor is a program which makes possible to store the source program in RAM and provides access to it directly for error correction, organisation or restructuring etc.
3) APPLICATION SOFTWARE :
It is a set of programs which are written by a compiler user or programer to meet their in formation processing requirements. These programs do specified jogs for the user. This software also known as package. The most applications are MS Word, MS Excel, Tally etc. without application software computer can run.