The Remington Rand Type 409-2 Electronic Computer

The Remington Rand Electronic Computer, Type 409-2, does computations by arithmetic steps in sequence with a unique self-proving feature. Parallel inputs to ten vacuum-tube decades are added or directly subtracted into a 22-column Accumulator. The Accumulator is connected in a ring so that a number or pair of numbers can be shifted to any position. Decimal positions are automatically handled by a Decimal Computer. Signs are handled algebraically. The total electron tube complement includes 1476 vacuum tubes and 1128 cold-cathode gas diodes. Most of these are designed and manufactured especially for computer use. Inputs are brought to the Accumulator, using a Call Line for each complete number, from three types of storage: 1. Variables from a tabulating card reading block of Sensing Switches; 2. Constants from manually settable Constant Switches; and 3. Intermediate results from Storage Relays. Outputs are delivered to Punching Storage from Intermediate Storage, in one or two blocks. Results are punched into the same tabulating card or following cards, as may be desired. Programming is directed by interchangeable Plug Boards. There are 40 Calculating Steps and 6 special steps: Clear, Set I, Set II, Sort I, Sort II and Trip. Each Calculating Step has 5 addresses and a process designation: 1st Operand; Process (+, -,×,÷); 2nd Operand; Result; Next Step if Result is "plus"; and next step if Result is "minus.