Marc McDonald

Marc McDonald is an American computer programmer who was Microsoft's first salaried employee, not counting Monte Davidoff, who wrote the math package for BASIC for a flat fee. In 1977 he designed and implemented the 8-bit File Allocation Table file system for the NCR 8200 data-entry terminal and for Microsoft's Standalone Disk BASIC-80. He also developed an 8-bit operating system called M-DOS or MIDAS, which Microsoft never released, but whose file system, a variant of FAT, influenced Tim Paterson's QDOS and through it the FAT12 file system of 86-DOS, which became the basis for MS-DOS and PC DOS. McDonald left Microsoft in January 1984, worked at Asymetrix on ToolBook and at Design Intelligence, rejoined Microsoft in December 2000 in its Windows Defect Prevention group, co-wrote The Practical Guide to Defect Prevention, and left again in September 2011.