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C language

structure of c program with example



Structure of C program

A C program is divided into six different sections. Those are as follows.

The six sections are,
  • Documentation
  • Link
  • Definition
  • Global Declarations
  • Main functions
  • Subprograms
Now let us learn about each of this layer in detail.

Documentation Section

The documentation section is the part of the program where the programmer gives the details connected with the program. He usually gives the name of the program, the details of the author and other details like the time of coding and description. It gives overview of the code.
Example
/*
File Name: Helloworld.c
*/
Normally documentation writes in a comment.

Comment
There are two types of comment in c language. Comment parts are not executed by the c program it means comment part is not displayed in the output.  
1) single line comment
2) multi line comment

Single Line Comments

Single line comments are produced by double slash \\. 

 Example
    #include<stdio.h>    
     void main(){    
    //printing information    
    printf("Hello C");    
}      

Multi Line Comments

Multi-Line comments are produced by slash asterisk \* ... *\. It can't be nested.
Syntax:

     /*  
    code 
    to be commented 
    */  
 Example
     #include<stdio.h>    
      void main(){    
      /*printing information   
      Multi-Line Comment*/  
       printf("Hello C");      
}    

Link Section

This part of the code is used to declare all the header files that will be used in the program. This leads to the compiler being told to link the header files to the system libraries.
Example
#include<stdio.h>

Definition Section

In this section, we define different constants. The keyword define is used in this part.
#define PI=3.14

Global Declaration Section

This part of the code is the part where the global variables are declared. All the global variable used are declared in this part. The user-defined functions are also declared in this part of the code.
float area(float r);
int a=7;

Main Function Section

Every C-programs needs to have the main function. Each main function has 2 parts. A declaration part and an Execution part. In the declaration part we declared all the variables. The execution part start with the curly brackets and ends with the curly close bracket. Declaration and execution parts are declared inside the curly braces.
void main()
{
int a=5;
printf(" %d", a);
}

Sub Program Section

 User-defined functions are defined in this section of the program.
int add(int a, int b)
{
return a+b;
}
Simple c Program
#include <stdio.h>
int main()
{
    printf("hello, world\n");
    return 0;
}
Output
hello world