A typical C program has a structured layout that consists of several important parts. Understanding this structure helps learners write correct, readable, and well-organized code. Below are the key components of a C program explained in a simple but professional way.

1.Header Files

Header files contain declarations for functions and libraries that your program needs.
They allow the program to use built-in functionality such as input/output operations, string handling, math functions, etc.

Common Header Files

Syntax

#include <header_name.h>

Example

#include <stdio.h>   // Allows use of printf() and scanf()
#include <math.h>    // Allows mathematical functions like sqrt()

2.main() Function

The main() function is the entry point of every C program.
Execution starts from the first line inside main() and ends when the program reaches the end or a return statement.

Two Valid Forms of main()

int main() {
    // code
}

int main(int argc, char *argv[]) {
    // code with command-line arguments
}

Example

int main() {
    printf("Hello, C Programming!");  
    return 0;  // Indicates successful execution
}

3.Statements and Blocks

Statements

A statement is a single instruction that ends with a semicolon.

Examples of statements

int x = 10;         // Declaration statement
printf("%d", x);    // Function call statement
x = x + 5;          // Assignment statement

Blocks

A block is a group of statements enclosed in curly braces {}.
Blocks are used in functions, loops, conditionals, etc.

Example of a block

{
    int a = 5;
    int b = 10;
    printf("%d", a + b);
}

Blocks help structure the program into logical sections.

4.Comments

Comments are notes in the code that the compiler ignores.
They make your code easier to understand for yourself and others.

Types of Comments

1. Single-line comment

// This is a single-line comment
int age = 20;  // Declaring a variable

2. Multi-line comment

/* 
   This is a multi-line comment.
   It can span multiple lines.
*/
int sum = 10 + 20;

Why comments are important

• Explain complex logic

• Improve code readability

• Help in debugging

• Make programs easier to maintain

Complete Example Showing All Parts Together

#include <stdio.h>   // Header file

// This is the main function
int main() {

    // Declare variables (statements)
    int a = 10;
    int b = 20;

    /* 
       Displaying the sum of two numbers
       This is a multi-line comment
    */
    printf("Sum = %d", a + b);

    return 0;   // End of program
}