The WDR paper computer or Know-how Computer is an educational model of a computer consisting only of a pen, a sheet of paper, and individual matches in the most simple case. This allows anyone interested to learn how to program without having an

electronic computer A computer is a machine that can be programmed to automatically carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic sets of operations known as ''programs'', wh ...

at their disposal. The paper computer was created in the early 1980s when computer access was not yet widespread in Germany, to allow people to familiarize themselves with basic computer operation and assembly-like programming languages. It was distributed in over copies and at its time belonged to the computers with the widest circulation. The Know-how Computer was developed by and Ulrich Rohde and was first presented in the television program WDR Computerclub (broadcast by

Westdeutscher Rundfunk (; "West German Broadcasting Cologne"), shortened to WDR (), is a German public broadcasting, public-broadcasting institution based in the States of Germany, Federal State of North Rhine-Westphalia with its main office in Cologne. WDR is a const ...

) in 1983. It was also published in German computer magazines mc and . The original printed version of the paper computer has up to 21 lines of code on the left and eight

register Register or registration may refer to: Arts, entertainment, and media Music * Register (music), the relative "height" or range of a note, melody, part, instrument, etc. * ''Register'', a 2017 album by Travis Miller * Registration (organ), ...

s on the right, which are represented as boxes that contain as many

match A match is a tool for starting a fire. Typically, matches are made of small wooden sticks or stiff paper. One end is coated with a material that can be ignited by friction generated by striking the match against a suitable surface. Wooden matc ...

es as the value in the corresponding register. A pen is used to indicate the line of code which is about to be executed. The user steps through the program, adding and subtracting matches from the appropriate registers and following program flow until the stop instruction is encountered. The instruction set of five commands is small but

Turing complete Alan Mathison Turing (; 23 June 1912 – 7 June 1954) was an English mathematician, computer scientist, logician, cryptanalyst, philosopher and theoretical biologist. He was highly influential in the development of theoretical comput ...

and therefore enough to represent all mathematical functions: * inc *register*: Add 1 to the register. * dec *register*: Subtract 1 from the register. * jmp *line*: Jumps to the specified line. * isz *register*: Checks if the register is zero. If so, skips a line. If not, continues normally. * stp: Stops the program. In the original newspaper article about this computer, it was written slightly differently (translation): * + = Add 1 to the contents of data register XX and increase (program step) by 1 * - = Subtract 1 from the contents of data register XX and increase (program step) by 1 * (J) = (Jump) to (line) XX * 0 = Check if the content of the data register XX is equal to 0. If so, then increase (program step) by 2; if no(t), then increase (program step) by 1 * Stop = Stop An emulator for

Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

is available on Wolfgang Back's website, but a JavaScript emulator also exists. 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 In mathematical logic and theoretical computer science, a register machine is a generic class of abstract machines, analogous to a Turing machine and thus Turing complete. Unlike a Turing machine that uses a tape and head, a register machine u ...

by Elmar Cohors-Fresenborg, but follows more the approach of

John Cedric Shepherdson John Cedric Shepherdson, FBA (7 June 1926 – 8 January 2015) was a British logician who was Henry Overton Wills Professor of Mathematics at the University of Bristol from 1976 to 1991. Early life and education Shepherdson was born in Hudder ...

and Howard E. Sturgis in their Shepherdson–Sturgis register machine model. A derived version of the paper computer is used as a "Know-How Computer" in

Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...

n school education.

See also

References

Further reading