Introduction to C Programming

C Language was originally developed at Bell Labs by Ken Thompson and Dennis Ritchie in th mid of 1970’s. It is one of the most popular procedural, general purpose, and high-level programming language used in all operating systems of today. Although C was designed for writing system software, it is also widely used for developing application software. C is one of the most popular programming languages of all the time and there are very few computer architectures for which a C compiler does not exist.

C has greatly influenced many other popular programming languages, most notably C++, which began as an extention to C. C supports different types of statements like sequential, selection, looping etc. Procedural programming concept is well supported in C, this helps in dividing the programs into function modules or code blocks.

Structure of C program:

Structure of a c program cosists of following parts:

document Section

link section

defination section

global declaration section

main()

{

}

Sub-program Section

function()

{

}

function2()

{

}

…

The document section consists of a set of comment lines giving the name of the program, the author and other details such as short description of the purpose of the program etc. The link section provides instructions to the compiler to link functions from the system library. The defination section defines all the symbolic constants.

The variables can be declared inside the main function or before the main function. Declaring the variables before the main function makes the variables accessible to all the functions in a C language program, such variables are called Global  Varialbes. Declaring the variables within main function or other functions makes the usage of the variables confined to the function only and not accessible outside. These variables are called Local Variables.

Every C program must have one main function. It contains different executable statements between the opening and closing braces. The sub-program section contains all the user-defined functions that are called in other main function. User-defined functions are generally placed immediately after the main function although they may appear in any order.