DOS executable

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DOS executable
File name extension	`.exe`
Magic number	MZ
Type of format	Binary, executable

The DOS MZ executable format is the executable file format used for .EXE files in DOS.

The file can be identified by the ASCII string "MZ" or the hexadecimal 4D 5A at the beginning of the file (the "magic number"), although, in fact, "ZM" or the hexadecimal 5A 4D works as well. "MZ" are the initials of Mark Zbikowski, one of the developers of MS-DOS. The MZ DOS executable file is newer than COM executable and differs from it. The DOS executable header contains relocation information, which allows multiple segments to be loaded at arbitrary memory addresses, and support executables larger than 64 KiB, but still suffering from low memory limits. Later those limits were bypassed using DOS extenders. MZ DOS executables can be run from DOS, and most Windows versions can execute them using a sort of emulation.

MZ DOS executables can be created by linkers, like MS linker, VALX or Open WATCOM's WLINK, additionally FASM can create them directly.