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Structure of C Program

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Structure of C Program

Structure of C Program

shape Introduction

"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.

shape Conceptual figure


shape Description

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.

shape Sections Table

Sections in Structure of C Program
Documentation Section
Link Section
Definition Section
Global Declaration Section
Main Function Section
Sub-programming Section

Documentation Section:

shape Description

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]  

shape Description

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:

shape Description

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

Global Declaration Section:

shape Description

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:

shape Description

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:

shape Description

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

shape Example

[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.


shape Key Points

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

shape Programming Tips

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