Mark "Zibo" Joseph Zbikowski (born March 21, 1956) is a former Microsoft Architect and an early computer hacker. He started working at the company only a few years after its inception, leading efforts in MS-DOS, OS/2, Cairo and Windows NT. In 2006 he was honored for 25 years of service with the company, the first employee to reach this milestone other than Bill Gates and Steve Ballmer. He is currently a technical adviser to several companies and a lecturer at the University of Washington.

He was the designer of the DOS executable file format, used in MS-DOS executable files, and his initials grace the headers of that file format: the magic number of this type of file is the ASCII string 'MZ' (0x4D, 0x5A).[1]

Early years

Zbikowski was born in Detroit, Michigan, in 1956. While attending The Roeper School from 1961 to 1974, he developed an interest in mathematics and computers. His 8th-grade performance in the Michigan Mathematics Prize Competition led to an invitation in an NSF-funded summer program at Oakland University where he became friends with Microsoft's Steve Ballmer and Jeff Sachs.

Zbikowski pursued Computer Science at Harvard (A.B. 1978) and at Yale (S.M. 1979). He was active in both universities' Gilbert and Sullivan Societies[2][3].


Ballmer recruited Zbikowski, who joined Microsoft in 1981. In March 1982 he replaced Tim Paterson as development lead and manager for Microsoft's MS-DOS 2.0, a position he held through DOS 4.0. His first major contributions were the addition of hierarchical directory structure to DOS 2.0 and installable device drivers. From March 1985 until 1991, he was on the architecture team for OS/2, development manager for file systems and device drivers, and technical advisor to Paul Maritz. The breakthrough concept of Installable File System in OS/2 is attributed to him.

Following the demise of the Microsoft/IBM joint development agreement, he was an architect, development manager and key contributor to Cairo, working for Jim Allchin and, later, Anthony Short. This led to Cairo's Object File System and content index efforts. In 1996, as Cairo migrated from being a standalone product to a technology source, Zbikowski worked under Lou Perazzoli on the Windows NT kernel, focusing on performance and size, before becoming architect and development manager for NT file systems in 1998.

In 2001, Zbikowski was a candidate for director of the Harvard Alumni Association.

Zbikowski retired from Microsoft in June 2006. In later years when asked why he was still working, Mark often said, “to set a good example for my children”.[citation needed]

Mark Zbikowski is affiliated with the following companies:


  1. 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."
  4. Parallels: : Pioneer Software Developer Joins Parallels as Senior Technical Advisor
  5. Seattle Virtualization Company illumita Attracts Key Industry Talent
  6. Advisory Team
  7. Blue Dot Launches Partner Program, Adds DOS’s MZ to Advisory Board

External links

de:Mark Zbikowski zh:馬克·茨柏克沃斯基

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