| 词条 | Digi-Comp II |
| 释义 |
The Digi-Comp II was a toy computer invented by John Thomas Godfrey[1] and manufactured by E.S.R., Inc. that used {{convert|1/2|in|mm|round=0.5}} marbles rolling down a ramp to perform basic calculations. A two-level masonite platform with guides served as the medium for a supply of marbles that rolled down an inclined plane moving plastic cams as they went. The plastic cams played the part of flip-flops in an electronic computer - as a marble passed one of the cams, it would flip the cam around - in one position, the cam would allow the marble to pass in one direction, in the other position, it would cause the marble to drop through a hole and roll to the bottom of the ramp. The Digi-Comp II platform measures {{convert|14 × 28.5|in|cm}}.[2] The Digi-Comp II was not programmable, unlike the Digi-Comp I, an earlier offering in the E.S.R. product line that used an assortment of plastic slides, tubes, and bent metal wires to solve simple logic problems. Computational powerComputer scientist Scott Aaronson analyzed the computational power of the Digi-Comp II.[2] There are several ways to mathematically model the device's computational capabilities. A natural abstraction is a directed acyclic graph in which each internal vertex has an out-degree of 2, representing a toggle cam that routes balls to one of two other vertices. A fixed number of balls are placed at a designated source vertex, and the decision problem is to determine whether any balls ever reach a designated sink vertex. Aaronson showed that this decision problem, given as inputs a description of the DAG and the number of balls to run (encoded in unary), is complete under log-space reduction for CC, the class of problems log-space reducible to the stable marriage problem. He also showed that the variant of the problem in which the number of balls is encoded in binary, allowing the machine to run for an exponentially longer time, is still in P. ReproductionsA slightly downscaled reproduction of the Digi-Comp II, made from plywood, is available from Evil Mad Scientist. This reproduction uses {{convert|11|mm|in|abbr=on|frac=16}} steel pachinko balls, and measures {{convert|10 × 24|in|cm}}.[3][4] Evil Mad Scientist also created a giant variant measuring around {{convert|4 × 8|ft|m|1}} in size that uses billiard balls. The Massachusetts Institute of Technology's Stata Center houses one copy of the giant version.[5] See also
References1. ^{{cite web|url=http://www.legacy.com/obituaries/lsj/obituary.aspx?n=john-thomas-godfrey-jack&pid=134332357 |title=John Godfrey Obituary - Lansing, MI | Lansing State Journal |publisher=Legacy.com |date= |accessdate=2019-01-09}} 2. ^{{cite web|url=http://www.scottaaronson.com/blog/?p=1902|title=The Power of the Digi-Comp II|last=Aaronson|first=Scott|authorlink=Scott Aaronson|date=4 July 2014|website=Shtetl-Optimized|accessdate=28 July 2014}} 3. ^1 {{cite web|title=Digi-Comp II: First Edition|url=https://shop.evilmadscientist.com/tinykitlist/637|website=Evil Mad Scientists (Shop)|accessdate=12 February 2018|language=en-gb}} 4. ^{{cite web|last1=Oskay|first1=Windell|title=The Making of the Digi-Comp II, First Edition|publisher=Evil Mad Scientist Laboratories|url=https://www.evilmadscientist.com/2013/makingdciife/|accessdate=12 February 2018}} 5. ^{{cite web|title=DigiComp II|url=https://cel60celebration.mit.edu/digicomp-ii|website=Cel 60 Celebration|accessdate=12 February 2018}} External links
2 : Mechanical computers|Educational toys |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。