Hello World!

A "Hello world" program is a computer program that outputs "Hello World" (or some variant) on a display device. The first known version of this program comes from Brian Kernighan's paper A Tutorial Introduction to the Language B from 1972 (chapter 7).

In it's first form it was used to show how to use external variables in B but since then it has become pretty much the standard example to show the very basic syntax and most simple program in any given programming language.

int main() {
    printf("Hello World");
    return 0;
}

On this page¹ you can find a bunch of source code examples in various programming languages.²