Online C Compiler

Welcome! You're about to use one of the most influential programming languages ever created. C is renowned for its efficiency and for giving the programmer close control over the computer's memory. It's the language that built operating systems (like Linux and Windows), databases, and countless other languages.

Learning C gives you a deep understanding of how computers work at a fundamental level. Our online C compiler lets you write, compile, and run your C code without any installation.

Write Your C Code: Enter your C source code into the editor window provided.

Click the Run Button: This action compiles your code and then executes the resulting program.

Check the Result: The output of your program will appear in the window below.

Your First C Program: "Hello, World!"

Let's begin with the timeless tradition. This simple program is the first step for every C programmer.

  #include <stdio.h>

int main() {
    printf("Hello, C adventurers on docodehere.com!\n");
    return 0;
}

#include <stdio.h>: This line includes the "Standard Input/Output" header file. This file gives us access to functions like printf().

int main(): This is the main function, where every C program begins its execution.

printf(...): This is the "print formatted" function. It's the standard way to print text to the console.

\n: This is a special "escape character" that means "new line." It moves the cursor to the next line after printing the message.

return 0;: This signals that the program has finished successfully.

Let's Try Something More: Swapping Two Numbers

This is a classic C exercise that demonstrates how variables work. We'll swap the values of two variables using a third, temporary one.

  #include <stdio.h>

int main() {
    int a = 5;
    int b = 10;
    int temp;

    printf("Before swap: a = %d, b = %d\n", a, b);

    // Swapping logic
    temp = a;
    a = b;
    b = temp;

    printf("After swap: a = %d, b = %d\n", a, b);

    return 0;
}

Notice the %d in the printf statement. This is a format specifier that tells printf to insert the value of an integer variable at that spot.

It means the programs are written as a series of steps or procedures (functions) that the computer follows in order. It focuses on the "how" to do things step-by-step.

This is a crucial distinction! A single equals sign (=) is for assignment (giving a value to a variable). A double equals sign (==) is for comparison (checking if two values are equal).

C gives you a lot of power, but it expects you to be precise. A missing semicolon, bracket, or a wrong type of variable can cause errors. The key is to look at the line number the compiler points to and check for simple mistakes first.

Enjoy your journey into the core of programming with C!