The MS-DOS MZ executable format is the executable file format used for .EXE files in MS-DOS.
The file can be identified by the ASCII string “MZ” (hexadecimal: 4D 5A) at the beginning of the file (the “magic number“). “MZ” are the initials of Mark Zbikowski, one of the developers of MS-DOS.[1]
The MZ MS-DOS executable file is newer than the COM executable format and differs from it. The MS-DOS executable header contains relocation information, which allows multiple segments to be loaded at arbitrary memory addresses, and it supports executables larger than 64 KiB; however, the format still requires relatively low memory limits. These limits were later bypassed using MS-DOS extenders.
The environment of an EXE program run by MS-DOS is found in its Program Segment Prefix.
Compatibility
MZ MS-DOS executables can be run from MS-DOS and Windows 9x-based operating systems. 32-bit Windows NT-based operating systems can execute them using their built-in Virtual MS-DOS machine (although some graphics modes are unsupported). 64-bit versions of Windows cannot execute them. Alternative ways to run these executables include DOSBox, DOSEMU and Wine.
MZ MS-DOS executables can be created by linkers, like Digital Mars Optlink, MS linker, VALX or Open Watcom‘s WLINK; additionally, FASM can create them directly.
See also
References
- ^ Inside Windows: An In-Depth Look into the Win32 Portable Executable File Format – MSDN Magazine, February 2002. “Every PE file begins with a small MS-DOS® executable. … The first bytes of a PE file begin with the traditional MS-DOS header, called an IMAGE_DOS_HEADER. The only two values of any importance are e_magic and e_lfanew. … The e_magic field (a WORD) needs to be set to the value 0x5A4D. … In ASCII representation, 0x5A4D is MZ, the initials of Mark Zbikowski, one of the original architects of MS-DOS.”