Different Parts of a C Program

Different Parts of a C Program

In this article, I will discuss the Different Parts of a C Program. Please read our previous article, where we discussed the Basic Syntax of a C Program.

Different Parts of a C Program

A C program can be broadly divided into several parts, each serving a specific function within the overall structure of the program. Here’s an overview of these different parts:

Documentation Section:
  • Purpose: Provide comments and documentation for the program.
  • Content: Includes explanations of the purpose and functionalities of the program, author details, creation and modification dates, and any other relevant information.
  • Syntax: Uses /* comment */ for block comments or // for single-line comments.
Link Section:
  • Purpose: Involves linking external libraries or header files.
  • Content: Contains preprocessor directives like #include <stdio.h> to include standard input-output library or other libraries needed for the program.
  • Syntax: #include directive.
Definition Section:
  • Purpose: Defines macro constants and global variables.
  • Content: Macro definitions (#define PI 3.14) and declarations of global variables.
  • Syntax: #define for macros, standard variable declaration for global variables.
Global Declaration Section:
  • Purpose: Declares global variables and functions.
  • Content: Global variables accessible throughout the program and function prototypes.
  • Syntax: Variable declarations and function prototypes (e.g., int max(int, int);).
Main() Function Section:
  • Purpose: The entry point of the program.
  • Content: Contains the main function where the program execution begins.
  • Syntax: int main() { /* code */ }.
Subprograms Section:
  • Purpose: Contains functions and subroutines.
  • Content: User-defined functions that perform specific tasks called within the main() function.
  • Syntax: Function definitions with a return type, name, parameters (if any), and a body (e.g., int max(int a, int b) { /* code */ }).

Each of these sections plays a vital role in the structure and execution of a C program, making it a modular, efficient, and maintainable piece of software. Here’s a simple example to illustrate these parts:

#include <stdio.h>  // Preprocessor directive

// Function declaration
void greet(void);

// Global variable
int times = 3;

int main() {
    // Local variable
    int i;

    // Loop statement
    for (i = 0; i < times; i++) {
        greet(); // Function call

    return 0;

// Function definition
void greet(void) {
    printf("Hello, World!\n");

In this example, #include <stdio.h> is a preprocessor directive, greet() is a function declaration, times is a global variable, main() is the main function, i is a local variable, the for loop and printf call are statements, and // introduces a comment. The function greet is defined after the main function.

In the next article, I will discuss Constants in C Language with Examples. Here, in this article, I try to explain the Different Parts of a C Program in detail, and I hope you enjoy this Different Parts of a C Program article.

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