Hello, World

Problem to Solve

Thanks to Professor Brian Kernighan (who taught CS50 when David took it!), “hello, world” has been implemented in hundreds of languages. Let’s add your implementation to the list!

In a file called hello.c, in a folder called world, implement a program in C that prints hello, world\n, and that’s it!


Here’s the actual code you should write! (Quite the hint, huh?) Best to type it yourself, though, rather than copy/paste, so that you start to develop some “muscle memory” for writing code.

#include <stdio.h>

int main(void)
    printf("hello, world\n");


Here’s a demo of what should happen when you compile and execute your program.

How to Begin

Execute cd by itself in your terminal window. You should find that your terminal window’s prompt resembles the below:


Next execute

mkdir world

to make a folder called world in your codespace.

Then execute

cd world

to change directories into that folder. You should now see your terminal prompt as world/ $. You can now execute

code hello.c

to create a file called hello.c in which you can write your code.

How to Test

Recall that you can compile hello.c with:

make hello

If you don’t see an error message, it compiled successfully! You can confirm as much with


which should list not only hello.c (which is source code) but also hello (which is machine code).

If you do see an error message, try to fix your code and try to compile it again. If you don’t understand the error message, though, try executing

help50 make hello.c

for advice.

Once your code compiles successfully, you can execute your program with:



Execute the below to evaluate the correctness of your code using check50, a command-line program that will output happy faces whenever your code passes CS50’s automated tests and sad faces whenever it doesn’t!

check50 cs50/problems/2024/spring/world


Execute the below to evaluate the style of your code using style50, a command-line program that will output additions (in green) and deletions (in red) that you should make to your program in order to improve its style. If you have trouble seeing those colors, style50 supports other modes too!

style50 hello.c

How to Submit

No need to submit this one!