Alguns exemplos de "Hello, world!" em várias linguagens de programação:

GNU Assembly - Linux x86:

.text
.global main
main:
	pushl	%ebp
	movl	%esp, %ebp
# hello
	movl	$len,%edx
	movl	$msg,%ecx
	movl	$1,%ebx # 1 = stdout
	movl	$4,%eax # 4 = sys_write
	int	$0x80 # kernel
# return 0
	movl	$0, %eax
	leave
	ret
.data
msg:
	.ascii	"Hello, world!\n"
	len = . - msg

GNU Assembly - Linux x86_64/AMD64:

.text
.global main
main:
	pushq	%rbp
	movq	%rsp, %rbp
# hello
	movl	$len,%edx
	movl	$msg,%ecx
	movl	$1,%ebx # 1 = stdout
	movl	$4,%eax # 4 = sys_write
	int	$0x80 # kernel
# return 0
	movl	$0, %eax
	leave
	ret
.data
msg:
	.ascii	"Hello, world!\n"
	len = . - msg

ANSI C - multiplataforma:

#include <stdio.h>

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

ISO C++ - multiplataforma:

#include <iostream>
 
using namespace std;

int main() {
  cout << "Hello, world!" << endl;
  return 0;
}

Fortran 77 - multiplataforma:

      program hello
      write(*,*) 'Hello, world!'
      stop
      end

Clipper - DOS:

? "Hello, world!"

[x]Harbour - multiplataforma:

PROCEDURE Main
  ? "Hello, world!"
RETURN

Pascal - multiplataforma:

program hello;
begin
  writeln('Hello, world!');
end.

Perl - interpretado:

print "Hello, world!\n";

PHP - interpretado:

<?php
  echo "Hello, world!\n";
?>

Erlang - multiplataforma:

-module(hello).

-export([main/0]).

main() ->
  io:fwrite("Hello, world!~n", []),
  init:stop().

Scala - multiplataforma:

object hello {
  def main(args: Array[String]) {
    println("Hello, world!")
  }
}

Scheme - multiplataforma:

(display "Hello, world!\n")

Python - interpretado:

print "Hello, world!"

COBOL - multiplataforma:

       IDENTIFICATION DIVISION.
       PROGRAM-ID. HELLO.
       PROCEDURE DIVISION.
           DISPLAY "Hello, world!".
           STOP RUN.