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Porting UNIX for its first commercial application

It soon became obvious that the PDP-7 machine, which the UNIX group didn't own, was becoming obsolete. In 1970, they proposed buying a PDP-11 for about $65,000. Two research department heads, Doug McIlroy and Lee McMahon, realized the benefits of the new operating system and supported the proposal. The PDP-11 arrived at the end of the summer. The system was so new no disk was available at the time, so the effort to port UNIX didn't begin until December.

[ Dennis Ritchie and Ken Thompson at the PDP-11 ]
Dennis Ritchie (standing) and Ken Thompson begin porting UNIX to the PDP-11 via two Teletype 33 terminals.

"During the protracted arrival of the hardware," Ritchie said, "the increasing usefulness of the PDP-7 UNIX made it appropriate to justify creating PDP-11 UNIX as a development tool, to be used in writing a more special-purpose system, text processing."

The first potential customer was the Bell Labs Patent Department, which was evaluating a commercial system to prepare patent applications. In developing UNIX to support text processing, the Computing Science Research Center supported three Patent Department typists who spent the day busily typing, editing, and formatting patent applications.

Ritchie said, "The experiment was trying, but successful. Not only did the Patent Department adopt UNIX, and thus become the first of many groups at the Laboratories to ratify our work, but we acquired sufficient credibility to convince our own management to acquire one of the first PDP 11/45 systems made.

"The rest," Ritchie said, "is history."

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