based on the Digi-Comp II mechanism Turing Tumble WDR paper computer CARDboard Illustrative Aid to Computation References External links The Old Computer Museum - Collection of old analog, digital and mechanical computers. System Source Computer Museum, providing a web simulator Extra-large recreation, video showing the multiplication of 13 × 3 on a scaled-up re-creation. Original Instruction Manual Digi-Comp II Replica - Instructions and files for creating your own Digi-Comp II Mechanical computers Educational toys