🪟 Microsoft Open Source MS DOS

Tom Smykowski
3 min readApr 28, 2024

On April 25, 2024, Scott Hanselman and Jeff Wilcox made a special announcement on the Microsoft Open Source Blog. Scott Hanselman is a Vice President of Developer Community, and Jeff Wilcox is the Head of Open Source Programms Office.

They write about Ray Ozzie and Mark Zbikowski. The latter one, is in fact the creator of the executable file format. If you’re unsure, you can open any EXE file on your Windows machine.

To do it, I’ve opened the Notepad2.exe with Notepad2 :) :

As you can see the first two characters in the file are MZ. Indeed these are initials of Mark Zbikowski.

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In the blog post the authors share the info that Ray Ozzie found floppy disks with MS-DOS 4.0 and they decided to open source it. If you don’t know what a floppy disk is, it’s like an old-school cloud on a spinning magnetic disk:

A floppy disk

Such disks were used to hold data, the most popular one (on the right bottom) held 1.44 MB of…

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Tom Smykowski

Software Engineer & Tech Editor. Top 2% on StackOverflow, 3mil views on Quora. Won Shattered Pixel Dungeon.