1120 decimal digits of π were known in 1949, before that record was shattered by ENIAC using vacuum tubes and punch cards [1].
This project explores whether EDSAC could in theory have matched or beaten the ENIAC record of 2037 decimal places by using paper tape for storage.
The idea of using magnetic tape as addressable auxiliary storage was discussed by the creators of EDSAC in 1956, lending some credibility to the idea [2] [3].
Eiiti Wada wrote a digit generator for EDSAC in 2022, based on Machin’s formula. It generates 500 digits using main memory (mercury-based delay lines) [4]. This effort demonstrates that the original EDSAC hardware probably lacked the capacity to match the ENIAC record.
This project demonstrates generating about 250 digits using main memory and many thousands of digits using paper tape as storage. There are many caveats:
A browser-based EDSAC simulator is included with extended IO instructions not present in the original hardware, but which could plausibly have existed:
Switching the input to paper tape might seem superfluous, since input is normally read from paper tape by default. The additional instruction is intended to draw a distinction between tape containing instructions and tape containing data from previous output to the perforator.
There are no instructions for seeking, rewinding or addressing the tapes, so from the programmer’s perspective storage appears as a write head followed by a read head on an infinite buffer.