CREEPER is a demonstration program which can migrate from computer to computer within the ARPA network while performing its simple task.”

Thomas, Robert H. Distributed Computation Research at BBN Dec 1974.

Creeper was an experimental mobile program written in 1971 by Bob Thomas at Bolt, Beranek and Newman Inc. The program was written in PDP-10 assembly and moved between TENEX systems over the ARPANET. As it moved Creeper printed a message similar to “I'M THE CREEPER : CATCH ME IF YOU CAN” on the Model 33 ASR teletype. The techniques developed in Creeper were later used in the McROSS air traffic simulator to allow parts of the simulation to move across the network.

Shortly after Bob demonstrated Creeper, Ray Tomlinson wrote an enhanced version which replicated instead of simply moving. Ray then wrote a program called Reaper which moved through the ARPANET removing copies of Creeper. The story of Creeper & Reaper inspired A K Dewdney to set up the initial version of Core War, describing Creeper & Reaper as “two programs doing battle in the dark and noiseless corridors of core”.



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  2. Thomas, Robert H. Distributed Computation Research at BBN. Massachusetts: Bolt, Beranek and Newman Inc, Dec 1974.
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