First Program – Hello World

Your First C Program

The tradition in programming is that the first program you write in any language prints "Hello, World!" on the screen. It tests that your development environment is set up correctly and shows you the basic structure of a program.

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

Line-by-Line Explanation

Line 1: #include <stdio.h>

This is a preprocessor directive. It tells the compiler to include the contents of the stdio.h (Standard Input Output) header file. This file contains the definition of printf() and scanf(). Without this line, printf would be unknown to the compiler.

Line 2: int main() { }

This is the main function — the entry point of every C program. When you run a C program, execution always starts from main(). The int before main means the function returns an integer value.

Line 3: printf("Hello, World!\n");

printf() is a library function that prints text to the screen. The text inside double quotes is called a string literal. \n is an escape sequence that means "newline" — it moves the cursor to the next line after printing.

Line 4: return 0;

The return 0; statement returns the value 0 to the operating system, indicating that the program ran successfully. A non-zero return value typically indicates an error.

How to Compile and Run

# Step 1: Save your file as hello.c
# Step 2: Compile
gcc hello.c -o hello

# Step 3: Run (Linux/Mac)
./hello

# Step 3: Run (Windows)
hello.exe

Variations

#include <stdio.h>
int main() {
    printf("Welcome to CodingEasily!\n");
    printf("Learning C Programming\n");
    printf("Beginner to Advanced\n");
    return 0;
}

Common Errors in First Program

Summary

• Every C program starts execution from main()
• #include <stdio.h> is needed to use printf and scanf
• Statements end with semicolon ;
• Code blocks are enclosed in curly braces { }
• printf() displays text, \n moves to next line
• return 0; signals successful program completion