Basic Skeleton of a Simple C Program

Look at this small program:

#include <stdio.h>   // Header file

int main() {           // main function starts
    printf("Hello from Tamil Technicians!\\n");  // statement
    return 0;          // program ended successfully
}

Almost all C programs follow this pattern:

• One or more header files at the top (#include <stdio.h>).
• Exactly one main() function – the starting point of the program.
• Curly braces { } to mark the beginning and end of main() and other blocks.
• One or more statements inside main() (like printf, calculations, etc.).
• An optional return 0; to say “program finished correctly”.

Header Files – Why Do We Need #include <stdio.h>?

A header file is like a “reference book” that tells the compiler about functions and symbols that exist elsewhere.

For example, the function printf() is not defined by you. It is provided by the C standard library. The declaration of printf() lives in the header file stdio.h.

#include <stdio.h>

When you write this line, you are telling the compiler: “Please include all declarations related to standard input/output functions like printf, scanf.”

Common Header Files in C

The main() Function – Where the Program Starts

For the operating system, main() is the entry point of your C program. When you run the program, the OS first calls main(). From there, your code starts executing line by line.

Common Forms of main()

int main() {
    // code
    return 0;
}

int main(int argc, char *argv[]) {
    // code that uses command-line arguments
    return 0;
}

For beginners, we usually use the first simple form: int main() { ... }

Statements, Semicolons, and Blocks

Inside main(), we write statements – these are the individual instructions the computer will execute.

• Every complete statement in C ends with a semicolon ;.
• A group of statements inside curly braces { ... } is called a block.

int main() {
    int a = 10;           // statement 1
    int b = 20;           // statement 2
    int sum = a + b;      // statement 3

    printf("Sum = %d\\n", sum);  // statement 4

    return 0;             // statement 5
}

Comments – Notes Inside Your Code

Comments are notes written for humans (you or other programmers). The compiler ignores them. They help explain what the code is doing.

// This is a single-line comment

/*
   This is a multi-line comment.
   You can write description here.
*/

Using comments is a good habit, especially when you are learning:

• Write comments in simple English or Tamil-English mix.
• Explain logic, formulas, and “why” you did something.

How Does C Code Run? (Compile & Execute Flow)

When you press “run” or type gcc program.c -o program, many things happen internally. Understanding this flow will make error messages less scary.

1. Preprocessing The preprocessor handles lines starting with # like #include, #define. It expands macros and brings in header file contents.
2. Compilation The compiler translates your C code (now after preprocessing) into assembly language, then into object code (machine code for individual files).
3. Linking The linker combines your object code with library code (for functions like printf) and produces a final executable file (e.g., a.exe or a.out).
4. Loading & Execution When you run the program, the OS loads the executable into memory, calls main(), and your instructions start executing line by line.

Example: A Small C Program With All Parts

This program reads two numbers and prints their sum:

#include <stdio.h>   // 1) Header file

int main() {           // 2) main function - program starts here
    int x, y, total;   // 3) variable declarations

    // 4) Input
    printf("Enter two integers: ");
    scanf("%d %d", &x, &y);

    // 5) Process
    total = x + y;

    // 6) Output
    printf("Total = %d\\n", total);

    return 0;          // 7) Program ended successfully
}

If you look carefully, you can clearly see:

• Header file at top.
• main() function with braces.
• Variables, input, processing, and output statements.
• Comments explaining each step.

Checklist Before Compiling Your Program

• Did you include the correct header files?
• Is there exactly one main() function?
• Are all opening braces { properly closed with }?
• Did you add semicolons ; after each statement?
• Are comments properly closed (for /* */)?

Suggested Featured Image Concept for This Post

When you create the thumbnail for this blog post, you can use an illustration with this idea:

• A laptop screen showing a C program skeleton with highlighted parts: #include <stdio.h>, int main(), and a printf line.
• Colored labels or callouts around the screen saying “Header File”, “main() – Start”, “Statements”.
• A Tamil technician explaining the code with a pointer/pen near the screen.
• Top text: “Structure of a C Program” and subtitle: “main(), Header Files & How Code Runs?”.