bit-widths, was Re: HP Laserjet ..again....

On Wednesday 22 September 2004 16:13, William Maddox wrote: --snip-- To the best of my knowledge, it was a leftover from punched cards. On a 650, 10 digits per word were used for storing data - and a punched card could hold 8 words of data (8x10=80 column punched card). "Instructions" had 2 digits OP code, 4 digits data address, 4 digits next address and sign. Given that most programmers were "graduating" from unit record machines (IBM 407, etc.) to program the 650 - they were used to "decimal everything". IBM didn't want to change the paradyme - at least not in early commercial systems. (Note that all of IBM's scientific computers [704, 709, Stretch, 709x, 704x, etc.] were pure binary). Internally, the 650 used bi-quinary which only requires 6 bits to represent one of 10 decimal digits. One bit (the "bi" in bi-quinary) represented "0" or "5" and what the other five bits represented was dependent on the state of the "bi" bit; i.e., "bi" bit --------- 0 1 --------- 0 5 1 6 2 7 3 8 4 9 Kinda shrewd - and helped early unit record folks in deal with simple binary and "mostly" decimal ;-) Lyle -- Lyle Bickley Bickley Consulting West Inc. http://bickleywest.com "Black holes are where God is dividing by zero"