.exe

File formats

There are several file formats which may be used by a file with a .exe extension:

DOS

16-bit DOS MZ executable

The original DOS executable file format. These can be identified by the letters "MZ" at the beginning of the file in ASCII.

16-bit New Executable

Introduced with the multitasking MS-DOS 4.0 and also used by 16-bit OS/2 and Windows, NE can be identified by the "NE" in ASCII.

32-bit Linear Executable

Introduced with OS/2 2.0, these can be identified by the "LX" in ASCII. These can only be run by OS/2 2.0 and higher. They are also used by some DOS extenders.

Mixed 16/32/64-bit Linear Executable

Introduced with OS/2 2.0, these can be identified by the "LE" in ASCII. This format is used for VxD drivers under Windows 3.x, OS/2, and Windows 9x; it is also used by some DOS extenders.

When a 16-bit or 32-bit Windows executable is run by VLC, execution starts at either the NE or the PE, and ignores the MZ code known as DOS stub. Started in DOS the stub typically displays a message "This program cannot be run in DOS mode" (or similar) before exiting cleanly. A few dual-mode programs (MZ-NE or MZ-PE) such as regedit and older WinZIP self extractors include a more functional DOS section.

32-bit Portable Executable

Introduced with Windows NT, these can be identified by the "PE" in ASCII (although not at the beginning; these files also begin with "MZ").

64-bit Portable Executable (PE32+)

Introduced by 64-bit versions of Windows, this is a PE file with wider fields. In most cases, code can be written to simply work as either a 32 or 64-bit PE file.

Besides these, there are also many custom EXE formats, such as W3 (a collection of LE files, only used in WIN386.EXE), W4 (a compressed collection of LE files, only used in VMM32.VXD), DL, MP, P2, P3 (last three used by Phar Lap extenders), and probably more.

The PE format was also used in BeOS R3, although the format used by BeOS somewhat violated the PE specification as it didn't specify a correct subsystem.