Home > On-Demand Archives > Q&A Sessions >

Live Q&A - Mysteries of the Ancients: Binary-Coded Decimal (BCD)

Clive "Max" Maxfield - Watch Now - Duration: 24:28

Live Q&A - Mysteries of the Ancients: Binary-Coded Decimal (BCD)
Clive "Max" Maxfield
Live Q&A with Clive "Max" Maxfield for the talk titled Mysteries of the Ancients: Binary-Coded Decimal (BCD)
italicssurround text with
boldsurround text with
**two asterisks**
or just a bare URL
surround text with
strikethroughsurround text with
~~two tilde characters~~
prefix with

Score: 0 | 1 month ago | 1 reply

Excellent talk on a subject I have dealt with in the past, but not with the same level of detail.
I remember working with an Intel 8042 microcontroller, and saw one of the instructions was DAA, or "decimal adjust accumulator after addition". It was meant to allow the programmer to add 2 packed BCD values using the regular binary ADD instruction, and then correct the result. Here is a WWW link describing this same instruction in the x86 instruction set:

Score: 0 | 1 month ago | no reply

Hi Michael -- thanks for the kind words -- a lot of the early micros had different ways of handling BCD -- as you say, some had a DAA instruction, others actually offered BCD addition and subtraction operations, and some just gave a soft of half (nybble) carry flag you could use to sort things out yourself.

Score: 0 | 1 month ago | 1 reply

For some reason, two's complement has always baffled me. I get it now.

Score: 0 | 1 month ago | no reply

My work here is done LOL

10:34:40	 From  Max Maxfield : Hi everyone :-)
10:37:31	 From  Bob Fish : Audio is fine, video stuck in the pipe i.e. none!?
10:37:58	 From  Matt Burkett : Video is fine for me too
10:38:03	 From  Thomas Schaertel : Video and audio is fine here too.
10:39:42	 From  Bob Fish : Cleared blockage ! Qu.) Binary Coded 'something else'?
10:42:29	 From  Ross K. : Hi Max! You alluded to a difference in borrowing (subtraction) between the US and England in the talk. Could you elaborate?
10:45:00	 From  Michael Kirkhart : https://rounding.to/understanding-the-bankers-rounding/
10:46:16	 From  Max Maxfield : https://www.clivemaxfield.com/diycalculator/popup-m-round.shtml
10:46:37	 From  Bob Fish : These slides are very well prepared ... thinking of doing a set for f.p (floating point) ... for next year?
10:50:08	 From  Michael Kirkhart : Are we?  Have you watched a clerk try to make change if they fail to enter the cash you have given them in their cash register?
10:51:08	 From  Max Maxfield : https://www.clivemaxfield.com/coolbeans/is-this-the-worst-programming-language-ever/
10:52:36	 From  Max Maxfield : ++++++++++[>+++++++>++++++++++>+++<<<-]>++.>+.+++++++
10:54:06	 From  Bob Fish : Re: Floating-point - May be when we grasp full Quantum processing, fractional bits won't be the problem explaining why even the IEEE continues to strive for standards improvements re. f.p
10:55:36	 From  Al Anway : I have Chuck Moore's ColorForth on my todo list to explore.
10:56:47	 From  Nick Moore : Whoa, I need to check that out.