"Structure of C Program" chapter gives clear explanation of various sections of C-programs. Any program is written and executed in various steps to give a desired output.Even if a small program is coded, it requires a structure.

Any C program need to follow a structure which consists of certain rules. The Structure of C Program can be as follows which has various sections.Some of the sections are essential and some of them are optional.

Documentation section is used for giving the comments regarding the title, author,more detailed information about the program etc. Eg: Single line comments [html]//sum  of two numbers[/html] Multi-line comments [html]/*Welcome to SPLessons You are reading C-programming tutorial This program is about summing of two numbers*/[/html]  

Link section is used to link the compiler to the library function using header files. Eg: [html]#include<stdio.h> #include<conio.h> #include<stdlib.h> #include<math.h>[/html]

Definition section consists of symbolic constants. Eg: [c]#define true 1[/c]

The variables used anywhere in the program are called as global variables. In this section, global variables are declared which can be also used in user-defined functions. Eg: [c]int x=10;[/c]

Main function section is the main part of the program. It mainly consists of two parts which are written between the braces {} and every line have to end with a semicolon(;). Declaration Section: In declaration section, all the required variables are declared which can be used in the executable part. Executable Section: In executable section, statements are given which are helpful in executing the program and giving the output. Eg: [c] { Function 1 Function 2 . . }[/c]

Sub-programming section consists of user-defined functions.These functions are called by the main function section.

[c] /*C basic structure example to find sum of two numbers */ //documentation section #include<stdio.h> //Link section int total; //Global declaration section int sum(int,int); //Function declaration section void main() //Main section { int a,b; printf("\n Enter the two numbers : "); scanf("%d %d",&a,&b); /* taking two numbers as input*/ total = sum(a,b); /* calling function.The value returned by the function is stored in total */ printf("\n The sum of two numbers is : %d ",total); getch(); } int sum ( int num1,int num2) //User defined section { int result; /* defining variable, its scope lies within function */ result = num1 + num2 ; /*adding two numbers*/ return (result) ; //definition section }[/c] Output: [c] Enter the two numbers : 1 2 The sum of two numbers is : 3 [/c] All the rules should be followed in every section to get a successful output from a program.

• C-Structure is built-up based on 6 sections.
• Execution starts from main section.
• Sub-programming section and definition sections are optional.

Using documentation section(comments) is the best practice because it explains the program clearly .