Expensive Desk Calculator

Expensive Desk Calculator by Robert A. Wagner is thought to be computing's first interactive calculation program.[1]

Expensive Desk Calculator
Original author(s)Robert A. Wagner
Initial release1960s
PlatformTX-0, PDP-1
WebsitePDP-1 Restoration Project

The software first ran on the TX-0 computer loaned to the Massachusetts Institute of Technology (MIT) by Lincoln Laboratory. It was ported to the PDP-1 donated to MIT in 1961 by Digital Equipment Corporation.[2]

Friends from the MIT Tech Model Railroad Club, Wagner and a group of fellow students had access to these room-sized machines outside classes, signing up for time during off hours. Overseen by Jack Dennis, John McKenzie and faculty advisors, they were personal computer users as early as the late 1950s.[1]

The calculators Wagner needed to complete his numerical analysis homework were across campus and in short supply so he wrote one himself. Although the program has about three thousand lines of code and took months to write, Wagner received a grade of zero on his homework. His professor's reaction was, "You used a computer! This can't be right." Steven Levy wrote, "The professor would learn in time, as would everyone, that the world opened up by the computer was a limitless one."[3][4]


  1. Alan Kotok (15 May 2006). The Mouse That Roared: PDP-1 Celebration Event Lecture. Computer History Museum (Google Video link). Retrieved on 22 June 2006. Kotok's description begins at 1:02.
  2. Robert M. Slade (26 January 1994). BKDECWRK.RVW: Review of "Digital At Work", Pearson, 1992. Retrieved on 22 June 2006
  3. Steven Levy (1984). Hackers: Heroes of the Computer Revolution (ISBN 0-385-19195-2) retrieved on 22 June 2006 at Project Gutenberg, p. 33
  4. Levy, Steven (2 January 2001). Hackers: Heroes of the Computer Revolution. Penguin (Non-Classics). ISBN 0-14-100051-1.

See also

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