> this month marks the fiftieth anniversary of the release of what

> would become a seminal, and is arguably the single most important,

> piece of social software ever created.

I'm flattered, but must point out that diff was just one of

a sequence of more capable and robust versions of 

proof(1), which Mike Lesk contributed to Unix v3. It, in 

turn, copied a program written by Steve Johnson before 

Unix and general consciousness of software tools. Credit

must also go to several people who studied and created

algorithms for the "longest common subsequence"

problem: Harold Stone (who invented the diff algorithm

at a blackboard during a one-day visit to Bell Labs), Dan

Hirschberg, Tom Szymanksi, Al Aho, and Jeff Ullman.

For a legal case in which I served as an expert witness,

I found several examples of diff-type programs

developed in the late 1960s specifically for preparing

critical editions of ancient documents. However, Steve 

Johnson's unpublished program from the same era

appears to be the first that was inspired as a general

tool, and thus as "social software".

Doug