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Re: Binary Coded Decimal

by Marshall (Abbot)
on Sep 18, 2012 at 07:00 UTC ( #994205=note: print w/replies, xml ) Need Help??

in reply to Binary Coded Decimal

BCD, Binary Coded Decimal is a system where each 4 binary bits represent a decimal digit. The hexadecimal digits A-F are not used in this representation.

This format is a bit odd nowadays (more normal would be ASCII decimal which takes 2 8 bit bytes instead of 2 4 bit nibbles, but that extra space is usually not of consequence). Anyway this is how to calculate the "digits". The integer "div" or modulo operation is only one machine instruction and the integer multiply is also only one machine instruction. I don't know how good Perl is at this. See Perl pack() and unpack() for how to cram these into one 8 bit value.

#!usr/bin/perl -w use strict; my @tests = (2,11,23,89,99); foreach my $num (@tests) { my $units = $num % 10; #modulo is the remainder my $tens = ($num - $units)/10; printf "decimal=%02d BCD=%04b %04b\n", $num, $tens, $units; } __END__ decimal=02 BCD=0000 0010 decimal=11 BCD=0001 0001 decimal=23 BCD=0010 0011 decimal=89 BCD=1000 1001 decimal=99 BCD=1001 1001

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