From: sfuld@alumni.cmu.edu.invalid   
      
   On 2/11/2026 3:04 PM, quadi wrote:   
      
   snip   
      
      
   > And I noticed that a lot of mathematical tables from the old days went up   
   > to 10 digit accuracy, and scientific calculators had 10 digit displays,   
   > calculating internally to a slightly higher precision.   
      
   The ten digit displays came from the design of the first electric   
   calculators, made by such companies as Friden and Monroe in the 1940s   
   and 50s).  They had ten rows of numeric keys (0-9), so that the   
   operator, who presumably had ten fingers (including thumbs) could   
   operate them quickly.  So 10 digits sort of became standard.  When   
   computers came along, and the designers wanted to use binary for them,   
   they needed 35 bits (including sign) to hold the ten digits.  Going with   
   36 bits allowed six six bit characters.  The requirement from the US   
   Navy (a major customer) for that precision led to the 36 bit Univac 1100   
   series being a 36 bit machine.  Once you have 36 bit integers, you might   
   as well use 36 bit floating point numbers, and then 72 bit double   
   precision floating point numbers as the 1100 series did.   
      
      
   --   
     - Stephen Fuld   
   (e-mail address disguised to prevent spam)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)