The Stochastic Computer was developed as part of a program of research on the structure, realization and application of advanced automatic controllers in the form of Learning Machines. Although algorithms for search, identification, policy-formation and the integration of these activities, could be established and tested by simulation on conventional digital computers, there was no hardware available which would make construction of the complex computing structure required in a Learning Machine feasible. The main problem was to design an active storage element in which the stored value was stable over long periods, could be varied by small increments, and whose output could act as a 'weight' multiplying other variables. Since large numbers of these elements would be required in any practical system it was also necessary that they be small and of low cost. Conventional analog integrators and multipliers do not fulfill requirements of stability and low cost, and unconventional elements such as electro-chemical stores and transfluxors are unreliable or require sophisticated external circuitry to make them usable. Semiconductor integrated circuits have advantages in speed, stability, size and cost, and it was decided to design a computing element based on standard gates and flip-flops which would be amenable to large-scale integration.