WDR paper computer

[1] This allows anyone interested to learn how to program without having an electronic computer at their disposal.

The Know-how Computer was developed by Wolfgang Back [de] and Ulrich Rohde and was first presented in the television program WDR Computerclub (broadcast by Westdeutscher Rundfunk) in 1983.

The instruction set of five commands is small but Turing complete and therefore enough to represent all mathematical functions: In the original newspaper article about this computer, it was written slightly differently (translation): [4] An emulator for Windows is available on Wolfgang Back's website,[5] but a JavaScript emulator also exists.

[6] Emulators place fewer restrictions on line count or the number of registers, allowing longer and more complex programs.

The paper computer's method of operation is nominally based on a register machine by Elmar Cohors-Fresenborg,[2][7] but follows more the approach of John Cedric Shepherdson and Howard E. Sturgis in their Shepherdson–Sturgis register machine model.

An example of the original pen and paper-based implementation of the WDR computer. The first instruction of an addition program is marked by the pen. The operands 4 and 5 have been stored in the two registers.
The code from the photo above running in an emulator, adding the numbers 4 and 5. After 19 program steps, the end result 9 is in register 1.
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