C Hello World: Your First Program – A Step‑by‑Step Guide

Below is a classic "Hello World" program written in C, followed by a detailed explanation of each component.

#include <stdio.h>   // Pre‑processor directive
int main(void)       // Main function declaration
{
    printf("Hello World");  // Output the string to the console
    return 0;                // Terminate the program
}

1. Pre‑processor Directive

The #include <stdio.h> directive tells the compiler to incorporate the Standard Input/Output library, where printf is defined. Including the appropriate header file is mandatory before using any function from that library.

Custom header files can also be included in the same way: #include <file‑name.h>. Place all #include statements at the top of your source file.

2. The main Function

Every C program must contain a main function. Common signatures include:

• int main(void)
• int main(int argc, char *argv[])

Using int main(void) signifies that the program does not accept command‑line arguments and will return an integer exit status. A return value of 0 indicates successful execution.

3. Code Structure

• Curly braces ({ }) delimit the body of main and any other functions.
• Each statement ends with a semicolon (;).
• The printf function prints the specified text to the console.

4. Running a C Program

Below are the typical steps to create, compile, and run a C program in a common IDE:

1. Create a new project and choose a C/C++ source file.
2. Configure the file path and name (ending with .c).
3. Save the file and click "Build & Run".

Once compiled, the output window should display:

Hello, World!

5. Summary

• The main function is essential for every C program.
• Header files must be included at the top of the source file.
• All C programs follow a consistent structural pattern.