In high school he collaborated with Alex Citron on a simulation of a major league baseball season called CWABL, standing alternatively for Computerized Winner Automatic Baseball League or Citroblamatic Whizamadingy Automatic Baseball League, which came to employ a pseudorandom number generator classmate Robert Goodman programmed on an electronic calculator for CWABL, which despite its name was otherwise run by manual table look-up.
Blank was frustrated by the computer's tiny vocabulary; when it parsed user inputs very few words were recognized. After thinking about the problem during his undergraduate years, he started work on his own adventure game using MDL, a computer language invented at MIT. Blank and a handful of friends wrote the original version of Zork on a PDP-10 while he was attending medical school at Albert Einstein College of Medicine in New York.
The free-play university version of Zork first became available on the MIT-DM PDP-10 in June 1977. It was then distributed by the Digital Equipment Corporation DECUS program and spread to many colleges in the United States and Canada.
Blank graduated from medical school in 1979 but the call of Zork was irresistible. He and several friends spent the next year developing a specialized computer language that they could use to program text adventures like Zork on the new microcomputers.
The Apple II's limited RAM required them to cut half of the original version of Zork. The new Zork for the Apple and the Radio Shack TRS-80, had a 600-word vocabulary. They founded the new company Infocom to publish the game and more like it.
In 1993 he teamed up with former Infocom writer Michael Berlyn to found Blank, Berlyn and Co.. The company's name was later changed to Eidetic. They initially published productivity software for the Apple Newton. Eidetic's Notion: The Newton List Manager became a hit and was ultimately bundled in all Newtons.
Marc returned to text adventures in 1997 when Activision producer Eddie Dombrower asked Blank and Berlyn to create a small promotional game, Zork: The Undiscovered Underground as promotion for the release of Activision's graphical game Zork: Grand Inquisitor.
Blank left Sony in 2004, where he focused on his email client for the Treo smartphone, ChatterEmail. On February 22, 2007, Blank announced he would no longer be "actively" working on ChatterEmail. Marc subsequently joined Palm, Inc. (who acquired ChatterEmail) and led the design and implementation of the Palm Pre's Email application. He worked in the Android group at Google from 2009 to 2012, and is now a Principal Engineer at Lab126 (Amazon.com).