🟢 Beginner · Lesson 04

First Program – Hello World

पहला 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.

hello.c – Your First C Program

#include <stdio.h>

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

Hello, World!

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

Terminal / Command Prompt

# 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

C Language – Multiple Lines

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

Welcome to CodeKaFunda! Learning C Programming Beginner to Advanced

Common Errors in First Program

Error	Cause	Fix
error: stdio.h not found	Missing #include	Add #include <stdio.h>
warning: implicit declaration of printf	Missing stdio.h	Add #include <stdio.h>
Missing ; before }	Forgot semicolon	Add ; after printf statement
undefined reference to main	No main function	Write int main() { }

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

आपका पहला C Program

Programming में tradition है कि किसी भी language में पहला program "Hello, World!" screen पर print करता है। यह test करता है कि आपका development environment सही setup हुआ है।

hello.c

#include <stdio.h>

int main() {
    printf("Namaste Duniya!\n");
    return 0;
}

Namaste Duniya!

Line-by-Line Explanation

Line 1: #include <stdio.h>

यह एक preprocessor directive है। यह compiler को कहता है कि stdio.h (Standard Input Output) header file को include करे। इस file में printf() और scanf() की definition है। इस line के बिना, compiler printf को नहीं पहचानेगा।

Line 2: int main() { }

यह main function है — हर C program का entry point। जब आप C program run करते हैं, execution हमेशा main() से शुरू होती है।

Line 3: printf("Namaste Duniya!\n");

printf() एक library function है जो text screen पर print करता है। Double quotes के अंदर का text string literal कहलाता है। \n newline escape sequence है — यह cursor को अगली line पर ले जाता है।

Line 4: return 0;

return 0; operating system को 0 return करता है, जो बताता है कि program successfully चला। Non-zero value typically error indicate करती है।

Compile और Run कैसे करें

Terminal / Command Prompt

# Step 1: hello.c नाम से save करें
# Step 2: Compile करें
gcc hello.c -o hello

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

# Step 3: Run करें (Windows)
hello.exe

Common Errors

Error	कारण	Fix
stdio.h not found	#include missing	#include <stdio.h> add करें
Missing ;	Semicolon भूल गए	printf के बाद ; add करें
undefined reference to main	main function नहीं है	int main() { } लिखें

सारांश

हर C program main() से execute होना शुरू होता है
#include <stdio.h> printf और scanf के लिए ज़रूरी है
Statements semicolon ; से खत्म होते हैं
Code blocks curly braces { } में होते हैं
printf() text display करता है, \n अगली line पर जाता है
return 0; successful completion signal करता है

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