Comment by mjevans

Which part of it?

8 bit tape? Probably the format the hardware worked in... not actually sure I haven't used real tapes but it's plausible.

36 bit per word computer? Sometimes 0..~4Billion isn't enough. 4 more bits would get someone to 64 billion, or +/- 32 billion.

As it turns out, my guess was ALMOST correct

https://en.wikipedia.org/wiki/36-bit_computing

Paraphrasing, legacy keying systems were based on records of up to 10 printed decimal digits of accuracy for input. 35 bits would be required to match the +/- input but 36 works better as a machine word and operations on 6 x 6 bit (yuck?) characters; or some 'smaller' machines which used a 36 bit larger word and 12 or 18 bit small words. Why the yuck? That's only 64 characters total, so these systems only supported UPPERCASE ALWAYS numeric digits and some other characters.