what is the smallest hello world program you ever wrote. i mean in file size, not source length. if possible please give source in any language, and compiler name if you remember.
Reading article Cubbi linked to, I realized, that you didn't specify OS, hardware or even format (com files which are plain processor instuctions vs proper executable which have tons of service information). So in theory we really can just make our own device which will print "Hello World" on command. And then we can make our program as small as 1 bit.