How to do very long division and mod operations

Posted on 2000-03-31
Last Modified: 2010-05-18
Does anyone have any ideas on how to implement in C, (or any other modern language) algorithms that will do long division and compute modulo values for very long numbers, on the order of 512 bits?  Most integers are 16, 32, or at most 64 bits.  Any known URLs about this subject would be helpful.  I would also be interested in any books that address the subject with good examples.
Question by:mzehner

Accepted Solution

stochastic earned 100 total points
ID: 2675430


Strangely, I am not finding many good URLs with ready downloadable code. Am tempted to write it myself :-)

- stochastic
LVL 22

Expert Comment

ID: 2675500
Donald E. Knuth
The Art of Computer Programming
Vol. 2

Expert Comment

ID: 2675914
i got idea for you
use strings instead of int or anyother

write your numbers in string's and make
the operations on it

operation +
first num 894
second num 327

the same with the other operations
what i mean is that you will have to do the operation by yourself for each place in the string

first the last place 4+7=11 so in the answer string you put 1 and move 1 forward
then 9+2+1<this 1 moved from the last>
=12 then you put 2 and move 1 to the next level
then 8+3+1<the 1 from the last level>=12
you put 2 in the answer string and
you put 1 in the next level of the answer string
How Do You Stack Up Against Your Peers?

With today’s modern enterprise so dependent on digital infrastructures, the impact of major incidents has increased dramatically. Grab the report now to gain insight into how your organization ranks against your peers and learn best-in-class strategies to resolve incidents.


Expert Comment

ID: 2675915
i made it with operation +
you can do that with all the other operations like /,%,*,-
LVL 10

Expert Comment

ID: 2679284
I can send you a code which will do all basic operations /, *, +, -, %, for integers any length and base. The functions are not very fast but well tested and gives you a first impress who to do so. Writen an email to because the code is to long to be pasted here.

Author Comment

ID: 2736802
Thanks for taking the time to answer.  Although this code should work, it performs division on long ASCII strings and I do not believe it will be fast enough for my application.

Author Comment

ID: 2736809
The "barnyard" web site was not helpful since it did long division over the web and the code seemed to be on the server side.  However the "bearcave" web site was helpful since it had several references to other documents which described long division algorithms.  The comment by cookre was also very good and I would have split the points between the two of you if I could.  I accepted this answer since some of the documents brought the theoretical algorithms closer to the practical.  It also referenced Knuth.  Thanks for posting your comments.

Featured Post

MIM Survival Guide for Service Desk Managers

Major incidents can send mastered service desk processes into disorder. Systems and tools produce the data needed to resolve these incidents, but your challenge is getting that information to the right people fast. Check out the Survival Guide and begin bringing order to chaos.

Question has a verified solution.

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

Suggested Solutions

Title # Comments Views Activity
Using unmanaged DLL from managed application 14 295
Read file descriptor 3 in C 14 113
C language IDE – Compilers installation 14 75
Global Keyboard Hooks Blocked 4 81
This tutorial is posted by Aaron Wojnowski, administrator at  To view more iPhone tutorials, visit This is a very simple tutorial on finding the user's current location easily. In this tutorial, you will learn ho…
Summary: This tutorial covers some basics of pointer, pointer arithmetic and function pointer. What is a pointer: A pointer is a variable which holds an address. This address might be address of another variable/address of devices/address of fu…
The goal of this video is to provide viewers with basic examples to understand and use structures in the C programming language.
The goal of this video is to provide viewers with basic examples to understand opening and writing to files in the C programming language.

831 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question