Talk:Binary-coded decimal/Archives/2020/January
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Is there an article about an algorithm that converts a binary value to BCD?
for example: convert the value 11111111 (binary) to 255 with each digit stored in separate bytes:
| 2 | 5 | 5 |
| 00000010 | 00000101 | 00000101 |
What I can do is: you simply divide by 10 repeatedly and each time, you use the remainder to place your digits, while the quotient (rounded down) is the next digit to be divided again. For example:
- 255/10 = Q:25 R:5 That is 5 would be placed in the ones place of the digit BCD storage (XX5).
- with the quotient in hand, divide by 10 again, which would be 25/10 = Q:2 R:5 store the remainder into the tens place (X55)
- again, with the new quotient in hand, divide by 10 again: 2/10 = Q:0 R:2 now write the remainder value in the hundreds place (255).
This only works with unsigned integers. For signed integers, simply flip the negative value to a positive (-5 turns into 5, for example), call the routine to write the digits in, and then place a minus sign before it (so 11111111 (255), XOR +1 would be 00000001, then BCD it, which spits out 1 in decimal, and place the minus sign to form -1). You can keep going based on how many digits you want to display.
I did this on Super Mario World ROM hacking when Akaginite developed the 32-bit/16-bit division. Joeleoj123 (talk) 21:49, 24 February 2018 (UTC)
Edit: Included how to convert. Joeleoj123 (talk) 00:38, 8 March 2018 (UTC)
- I'm sorry... I thought I replied to this. I was certainly intending to. In general we don't include algorithms, particularly not if they're obvious or very well known. This one is widely covered in the literature, eg places like IBM's "Commercial Subroutine Package" (which dates from the 1960s) and, well, this one is obvious (or should be) to anyone in a first-year programming course and so has been "invented" countless times already. Jeh (talk) 03:12, 8 March 2018 (UTC)