Structure of C program

Structure of C program

Every C program consists of one or more modules called functions. One of the functions must be called main. The program will always begin by executing the main function. Any other function definitions must be defined separately, either ahead or after main function.

Each function must contain :

i.                    Heading :

A function heading, which consists of the function name, followed by an optional list of arguments, enclosed in parentheses.

ii.                  Declarations :

A function declarations, if arguments are included in the heading.

iii.                Compound statement :

A compound statement, which comprises the reminder of the function.

 The structures of a C language program is given below :

Document Section

Header Files

Definition sections / Symbolic Constants

Global Declaration section

Main() function section { Declaration part Executable part }

Subprogram section Function 1 Function 2 ………………. ………………. Function n (user-defined functions)

1.       Document section :

Document 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.

2.       Header :

Header files are used for inclusion of functions from the C language library.

3.       Definition section :

Definition section defines all symbolic constants. Symbolic constants are used for better understanding of certain names that are not going to change throughout the program.

4.       Global declaration section :

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

5.       Declaration part and Executable part :

Every C language program must have one main() function section. This sections contains two parts :declaration parts and executable part. The declaration part declares all the variables used in the executable part. There should be at least one statement in the executable part. The two parts must appear between the opening and the closing braces. The program execution beings 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 end with a semicolon.

6.       Subprogram section :

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

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