Lesson 1 · 1 of 20

Hello, world · C

Write your first C program: include stdio.h, create the main function and print text on the screen with printf, \n and \t.

C · Hello, world in DMarlon Studio: the example's code and its output in the terminal

Every C program starts with the libraries it needs. #include <stdio.h> brings in the standard input and output functions, including `printf`, which writes text on the screen. Lines starting with // are comments: the compiler ignores them and they are there to explain the code.

The program always starts running in the `main` function. int main(void) says that main takes nothing and returns a whole number; its code goes between braces { } and every statement ends with a semicolon ;.

printf writes the text exactly as given, without starting a new line. That is why "One, ", "two, " and "three!\n" end up together on one line: only `\n` moves to the next one. In the same way, `\t` inserts a tab for simple columns and \" puts quotes inside the text.

return 0; ends main and tells the system that everything went well. In DMarlon Studio, C is written in the Console target: press F9 and the program is compiled and run in one click, with the output right there.

Code · main.c

// stdio.h brings printf, which writes text on the screen.#include <stdio.h>// Every C program starts running in main.int main(void) {    printf("Hello, world!\n");    printf("Welcome to the C course.\n");    // \n starts a new line; without it, the text carries on.    printf("One, ");    printf("two, ");    printf("three!\n");    // \t inserts a tab, handy for simple columns.    printf("Day\tWeather\n");    printf("Mon\tSunny\n");    printf("Tue\tRainy\n");    // \" writes quotes inside the text.    printf("She said \"C is fast\".\n");    return 0;  // 0 tells the system that all went well}

Output · cc main.c -o main && ./main

Hello, world!
Welcome to the C course.
One, two, three!
Day	Weather
Mon	Sunny
Tue	Rainy
She said "C is fast".

Key points

#include <stdio.h> gives you printf.
The program starts in int main(void).
Every statement ends with ;.
printf does not start a new line: add \n.
return 0; means the program finished fine.

Exercise

Add three more days (Wed, Thu, Fri) with their weather at the end, lined up with \t, and a goodbye line.