Chapter Software at a glance


As you know, software is a collection of programs and a program is a set of instructions written in a programming language.Using software, user , user interacts with the computer. It controls and governs the operation of a computer system. Software can typically be classified into three categories :
1. System software (operating system)
2. Development software (Language processor)
3. Application software.

SYSTEM SOFTWARE (Operating System)

Operating system is the most important system software for operating any computer. It has a set of special commands to instruct the computer, what action to be performed.
In other words, an operating system is a program which acts as an interface between a user and the computer hardware. There are different types of operating system available, like linux, window, dos etc.


DOS (Disk Operating System) is developed by Microsoft Corporation, a USA based software company, therefore it is now called MS-DOS or Microsoft Disk Operating System. It is one of the most important single user operating system used earlier. It must be loaded in the memory before user can interacts with the machine.
We have no control over the hardware that is inside the computer. We can interact with the outer hardware like, keyboard, mouse , monitor and printer. When we input the data to the computer through the keyboard or the mouse , MS-DOS translates this data into signals.The processor of the computer understands these signals and follows them.


It is easy to write programs in High level languages (HLL) because it uses written in ENGLISH like sentences. But computer does not understand any other language rather than its own machine language which is based on two binary digits (0 and 1 ). So, a system program is developed to translate a High Level Language into machine language so that a computer can understand it . This system program is called language processors. There are three language processors:
(i) Assembler
(ii) Interpreter
(iii) Compiler


Application software is a set of programs to perform a specified application. It is developed by the programmers to enable computers to execute a particular job such as writing a letter , involving, drawing pictures, solving sums , playing games etc. Some application software are MS-WORD, MS-EXCEL, TALLY etc.


Computer can understand only machine language to carry out their jobs.But it is difficult to write programs using machine language in binary (0 and 1).
Computer languages provides an environment to user so that user can write his program in english like sentences, and then Language compiler/interpreter translate these programming sentences into appropriate machine language. There are two types of programming languages as under :

(a) Low-level Programming Languages
(b) High-level Programming languages


Low-level programming language is used for system programming. It means a program which is developed for the hardware to instruct them as per the desire of programmer. This language is very close to the machine language of the computer.So, it is difficult to learn this language. A low- level programming language is translated into machine code by an assembler.


These languages are almost similar to the English language. So, it is easy to program in High Level Language. A high level language is translated into machine code by a compiler or an interpreter. Some popular high level languages are BASIC, COBOL, C < VISUAL BASIC. These languages can be used on almost all types of computer.

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