Basic structure of C program

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Basic structure of C program :

The examples discussed so far illustrate that a C program can be viewed as a group of building blocks called functions. A function is a subroutine that may include one or more statements designed to perform a specific task. To write C program, we first create functions and then put them together. A C program may contain one or more sections as following :


The documentation section consists of a set of comment lines giving the name of the program, the author and other details, which the programmer would like to use later. The link section defines all symbolic constants.

There are some variables that are used in more than one function. Such variables are called global variables and are declared in the global declaration section that is outside of all the functions. This section also declares all the use-defined functions.

Every C program must have one main() function section. This section contains two parts, declaration part and executable part. The declaration part declares all the variables used in the executable part. 

There is at least one statement in the executable part. These two parts must appear between the opening and the closing braces. The program execution begins at the opening brace and ends at the closing brace. The closing brace of the main function section is the logical end of the program. All statements in the declaration and executable parts end with a semicolon( ; ).

The subprogram section contains all the user-defined functions that are called in the main function. User-defined functions are generally placed immediately after the main function, although they may appear in any order.

All sections, except the main function section may be absent when they are not required.

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