Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win

x
Solved

# BCD

Posted on 2002-06-13
Medium Priority
279 Views
Does anyone know of a BCD (Binary coded decimal) library available for C?
0
Question by:philsmicronet
[X]
###### Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

• Help others & share knowledge
• Earn cash & points
• 4
• 3
• 2
• +2

LVL 86

Expert Comment

ID: 7075616
Hmm, I cannot see the need for a lib, as BCD is pretty straight foward:

The Binary Coded Decimal, or BCD code, is used as the direct code to communicate decimal numbers using
a binary code. Recall that the decimal numbers are 0 to 9.  BCD code is used to directly translate these
decimal numbers using a 4-bit code.
Here are the decimal equivalent 4-bit BCD codes;

Decimal BCD
0 0000
1 0001
2 0010
3 0011
4 0100
5 0101
6 0110
7 0111
8 1000
9 1001

Notice that each single decimal digit has an equivalent 4-bit BCD code.

Converting Decimal to BCD

This conversion simply requires you to represent each decimal digit with its 4-bit BCD code.

Eg.  38210 = (310 = 0011BCD), (810 = 1000BCD) and (210 = 0010BCD)  so;
the result is 001110000010BCD   and dropping the leading zeros = 1110000010BCD

Converting BCD to Decimal

This is just grouping every 4 bits of BDC code (starting at the LSD) and representing each 4-bit code
with its equivalent decimal number.

Eg.  100100101000BCD = (1000 = 8), (0010 = 2) and (1001 = 9)   so;

the decimal equivalent is 92810

Nevertheless, check out this one: http://www.1cplusplusstreet.com/vb/scripts/ShowCode.asp?txtCodeId=625&lngWId=3 ("BCD math")
0

LVL 1

Author Comment

ID: 7076777
0

LVL 86

Expert Comment

ID: 7076783
That is why I provided the link :o)
0

LVL 1

Author Comment

ID: 7076885
This allows you to convert from BCD to double and back, however, if you do this you are going to still have the same rounding problems that you would normally have with floating point arithmetic. I would have thought that generic BCD add, subtract etc etc would be required.
0

LVL 11

Expert Comment

ID: 7077536
"BCD math library C source" on Goolge gives you scores of links.
0

LVL 8

Expert Comment

ID: 7080533
@ robert_marquardt:
True, google gives you scores of links -- but 'quantity' is spelled differently from 'quality'.

@ philsmicronet:
Basically, any x86-processor supports BCD's. I didn't find a link with a BCD math library. However, this might be useful to you:
http://www.intel.com/design/intarch/techinfo/Pentium/instsum.htm
Search for "Packed BCD Adjustment Instructions"/"Unpacked BCD Adjustment Instructions" -- it deals with double/single-digit BCD's only, but can easily extended to multi-digit-BCD's. It is 16-bit code so don't expect any high-performance-operations. Anyway, here are some ASM-code-snippets:

mov ax,9        ;ax = 0x0009
mov bx,3        ;bx = 0x0003
add al,bl       ;ax = 0x000c = 12d
aaa             ;ax = 0x0102

Multiply [using aam = "ascii adjust after multiply"]:
mov al,5        ;al = 0x0005
mov bl,7        ;bl = 0x0007
mul bl          ;ax = al *  bl = 0x0023 = 35d
aam             ;ax = 0x0305

Hope that provides at least some help to you. Regards,
.f
0

LVL 3

Accepted Solution

jimbucci earned 400 total points
ID: 7126696
Sounds like a Data Structures I project I did many years ago.  The code is in Pascal, but I was able to add and subtract BCD numbers.

1st of all - is this homework?

If not, and if I can find the code, would you be interested in it?

Jim
0

LVL 1

Author Comment

ID: 7126762
No, its just aprogram I am working on.
0

LVL 86

Expert Comment

ID: 9715016
Wow, that was really a quick accept - so, now, would you be so kind and explain why you accepted an answer that reads " if I can find the code, would you be interested in it?" over the others that had good suggestions? As for my part, this is not really motivating to help you in the future.
0

LVL 3

Expert Comment

ID: 9715086
I'm puzzled as well.  Must have been a mouse click error.
Jim
0

LVL 1

Author Comment

ID: 9717577
Oooops. Was going through my old questions that I had not accepted (only two) and selected the wrong comment.
0

## Featured Post

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

In this article, I will show how to use the Ribbon IDs Tool Window to assign the built-in Office icons to a ribbon button.  This tool will help us to find the OfficeImageId that corresponds to our desired built-in Office icon. The tool is part ofâ€¦
zlib is a free compression library (a DLL) on which the popular gzip utility is built.  In this article, we'll see how to use the zlib functions to compress and decompress data in memory; that is, without needing to use a temporary file.  We'll be câ€¦
This is Part 3 in a 3-part series on Experts Exchange to discuss error handling in VBA code written for Excel. Part 1 of this series discussed basic error handling code using VBA. http://www.experts-exchange.com/videos/1478/Excel-Error-Handlinâ€¦
In this video, Percona Director of Solution Engineering Jon Tobin discusses the function and features of Percona Server for MongoDB. How Percona can help Percona can help you determine if Percona Server for MongoDB is the right solution for â€¦
###### Suggested Courses
Course of the Month10 days, 20 hours left to enroll