<i>The header of an EXE file begins with the magic letters “MZ".</i> = Broken Link.<p>The 'MZ' letters were the initials of the programmer who made the 'EXE' format. I can't remember his name today, though I used to know it 30 years ago. ("Mike"?? The "Z" part was an Italian surname, IIRC.) That 'magic number' was following in the footsteps of many other programmers who began their file formats with 'magic' letters or numbers.<p>In the UNIX world, there was a file called /etc/magic which contained a list of all the 'magic numbers', though this has been superseded by more modern compiled lists. To find what sort of file a particular file is, use the 'file' command which accesses the same data as the previous /etc/magic file did.<p>file cli-32.exe<p>gives an answer<p>cli-32.exe: PE32 executable (console) Intel 80386, for MS Windows