Editing UNIVAC I (section)

===Instructions and data===
[[Instruction set|Instructions]] were six [[alphanumeric]] characters, packed two instructions per word. The addition time was 525 [[microseconds]] and the multiplication time was 2150 microseconds. A non-standard modification called "Overdrive" did exist, that allowed for three four-character instructions per word under some circumstances. (Ingerman's simulator for the UNIVAC, referenced below, also makes this modification available.){{citation needed|date=July 2022}}

[[File:UNIVAC I Interior.jpg|thumb|Internal view of UNIVAC I]]
Digits were represented internally using [[excess-3]] ("XS3") [[binary-coded decimal]] (BCD) arithmetic with six bits per digit using the same value as the digits of the alphanumeric character set (and one [[parity bit]] per digit for [[redundancy check|error checking]]), allowing 11-digit [[signed number representations#Sign–magnitude|signed magnitude]] numbers. But with the exception of one or two machine instructions, UNIVAC was considered by programmers to be a decimal machine, not a binary machine, and the binary representation of the characters was irrelevant. If a non-digit character was encountered in a position during an arithmetic operation the machine passed it unchanged to the output, and any carry into the non-digit was lost. (Note, however, that a peculiarity of UNIVAC I's addition/subtraction circuitry was that the "ignore", space, and minus characters were occasionally treated as numeric, with values of –3, –2, and –1, respectively, and the apostrophe, ampersand, and left parenthesis were occasionally treated as numeric, with values 10, 11, and 12.){{citation needed|date=July 2022}}