There's a fabulous article from Raymond Chen about EXE headers in general: https://blogs.msdn.microsoft.com/oldnewthing/20060130-00/?p=32483 https://blogs.msdn.

There's a fabulous article from Raymond Chen about EXE headers in general: https://blogs.msdn.microsoft.com/oldnewthing/20060130-00/?p=32483 https://blogs.msdn.microsoft.com/oldnewthing/20060130-00/?p=... >A Win32 executable file begins with a so-called "MZ" header, followed by a so-called "PE" header. If the "PE" header cannot be found, then the loader attempts to load the program as a Win16 executable file, which consists of an "MZ" header followed by an "NE" header. >If neither a "PE" nor an "NE" header can be found after the "MZ" header, then the loader attempts to load the program as an MS-DOS relocatable executable. If not even an "MZ" header can be found, then the loader attempt to load the program as an MS-DOS non-relocatable executable (aka "COM format" since this is the format of CP/M .COM files).