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Convert Integers to Their Textual Description

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6 May 2014Apache2 min read 157.6K   1.3K   27   52
Convert an integer to its textual description

Sample Image


Ever wanted a friendlier way to display any given amount to a user? Or, perhaps you're coding a grammatically correct English application, racing game, tracking visitors, or creating an accounting solution. Whatever the case, there are some times when a programmer needs to represent a number as a written word (i.e., 4 becomes "four"). And, that's the goal of this routine.

The original version (as most typical implementations of this) used strings for calculations and conversions and while it worked, it was slower. However, I updated the algorithm to not do this anymore. As a result, I noticed an average 310% speed increase (on a Pentium IV) despite the fact I also added support for much larger numbers as well.


Using this routine is straightforward. It does make use of C-style strings as they are fast and extremely portable with most environments. The sole routine that does the grunt work is named GetNumWord() and is prototyped as follows...

// prototype/signature
char *GetNumWord (long long llNumber, char *szDest, 
                  unsigned int unLen, bool bOrdinal, bool bUseAnd);

Parameter Descriptions:

llNumber = This is the 64-bit number to convert.
szDest = Pointer to the output buffer (char array).
unLen = Size in bytes of the output buffer (not string length).
bOrdinal = Setting this to true will return the ordinal version of the number (e.g., first); otherwise, the cardinal version is returned (e.g., one).
bUseAnd = This will determine if the and conjunction is used in the output or not (e.g., One Hundred And One).


char szBuffer[100] = {0};
GetNumWord(5001, szBuffer, sizeof(szBuffer), false, false);
GetNumWord(-10, szBuffer, sizeof(szBuffer), false, false);
GetNumWord(123, szBuffer, sizeof(szBuffer), true, true);

Will return...

"Five Thousand One"
"Negative Ten"
"One Hundred And Twenty-Third"


The function takes a long long as the number parameter. On most 32-bit and 64-bit systems, this means the lowest number you can pass is <nobr>-9,223,372,036,854,775,808 and the highest number is 9,223,372,036,854,775,807.

Also, 64-bit arithmetic on a 32-bit CPU is a bit slower. However, the difference is negligible for most applications, and 64-bit CPUs are becoming more and more mainstream, so this consideration will soon be obsolete.

Credits & History

<nobr>Article's Author<nobr> - Jeremy Falcon
<nobr>The "and" Conjunction Suggestion<nobr> - benjymous
<nobr>Memory Leak Tip<nobr> - James Curran
  • <nobr>2007-01-13 - Ver. 2.0 released.
  • <nobr>2002-04-12 - Ver. 1.1 released.
  • <nobr>2002-04-01 - Ver. 1.0 released.


Permission is granted to anyone to use this software for any purpose on any computer system, and to alter it and redistribute it freely, subject to the following restrictions found in NumWord.c. It's nothing big. Essentially, it states that if your computer blows up then it's not my fault, and if you use this code then give credit where it's due.


This article, along with any associated source code and files, is licensed under The Apache License, Version 2.0

Written By
Team Leader
United States United States
I've been in software development since 1994. Over the years I've learned quite a lot in what it takes to complete the process of pushing out a quality product to customers in a timely fashion. As most of my colleagues could attest, there have been many challenges in our new and growing field in the past couple of decades as the industry matures rapidly. Much more so than most others historically speaking.

As such, I've learned one of the best aspects of software engineering is embracing the change that inherently comes along with it as new technologies constantly emerge to help us improve our world one application at a time as we make sense of the overwhelming amount of data now prevalent in the Information Age.

We truly live in a time unlike that ever known to mankind in recorded history, and it is my hope to do my part to help it along to face the challenges and demands of tomorrow.

Comments and Discussions

QuestionComments on the code. Pin
Bill_Hallahan14-May-14 16:40
Bill_Hallahan14-May-14 16:40 
AnswerRe: Comments on the code. Pin
Jeremy Falcon14-May-14 17:05
professionalJeremy Falcon14-May-14 17:05 
GeneralRe: Comments on the code. Pin
Bill_Hallahan15-May-14 17:24
Bill_Hallahan15-May-14 17:24 
GeneralRe: Comments on the code. Pin
Jeremy Falcon16-May-14 4:56
professionalJeremy Falcon16-May-14 4:56 
GeneralRe: Comments on the code. Pin
Bill_Hallahan16-May-14 23:34
Bill_Hallahan16-May-14 23:34 
GeneralRe: Comments on the code. Pin
Jeremy Falcon16-May-14 5:01
professionalJeremy Falcon16-May-14 5:01 
GeneralRe: Comments on the code. Pin
Bill_Hallahan16-May-14 23:21
Bill_Hallahan16-May-14 23:21 
GeneralRe: Comments on the code. Pin
Jeremy Falcon16-May-14 6:31
professionalJeremy Falcon16-May-14 6:31 
GeneralRe: Comments on the code. Pin
Bill_Hallahan17-May-14 0:17
Bill_Hallahan17-May-14 0:17 
GeneralRe: Comments on the code. Pin
Jeremy Falcon17-May-14 4:53
professionalJeremy Falcon17-May-14 4:53 
GeneralRe: Comments on the code. Pin
Bill_Hallahan17-May-14 10:23
Bill_Hallahan17-May-14 10:23 
Jeremy, I know how to program, I've been doing it for 35 years. You are confusing a tired person making mistakes with a lack of knowledge and experience, and your comment is disrespectful towards someone you do not know.

I now realize from your last post that you are confusing a technical review with someone trashing you. In my post, I referred to code and the algorithm, not to you. And, at least one thing I wrote is correct.

All you had to write is, "your wrong, it works", and I would have re reviewed the code again, and realized my error. You actually did that with the issue of the return-type of the function, and I agreed immediately.

And, you wrote about improving performance. If you care about performance, I gave you some useful advice. I even offered the code. After looking the cycle times for the integer divide instruction for the Pentium IV processor mentioned in your article, I now realize that the algorithm I proposed would result in a huge speedup.

An 32-bit integer divide instruction takes about 387 cycles on an Intel X9650 processor. It's about the same number of cycles on both a 32-bit and the 64-bit architecture. Of course, caching issues and bus speeds are a factor for the speed of a program too, but based on that number of cycles, the algorithm in Seminumerical algorithms should be much faster than the divide algorithm used in the current code. And, the Pentium IV processor takes at least as many cycles as the 9650 for an integer divides, if not more.

The Pentium IV is a 32-bit processor, so it will take more than a single divide instruction to do a 64-bit divide.

On the more modern core i5 processors, an integer divide is about 40 cycles, so the algorithm you use might be fast enough on those. I suspect it will still be slower than the algorithm in the book, but I don't know that for sure. On a Pentium IV, the processor you mention in your article, the better algorithm will be significantly faster.

Again, it's the base 10 conversion algorithm in "Seminumerical Algorithms" by Donald Knuth.

If you want, I'll post the fast base 10 conversion code here, and it will drop right into your code with little change. I am not trashing you by doing that. I would never do that. I wouldn't have started and ended my initial post with "Nice job" if I meant to trash you.

Best wishes

modified 26-May-14 1:40am.

GeneralRe: Comments on the code. Pin
Jeremy Falcon18-May-14 5:15
professionalJeremy Falcon18-May-14 5:15 
GeneralRe: Comments on the code. Pin
Bill_Hallahan25-May-14 20:31
Bill_Hallahan25-May-14 20:31 
QuestionAn Actor that write code? Pin
Member 761463224-Nov-13 20:00
Member 761463224-Nov-13 20:00 
AnswerRe: An Actor that write code? Pin
Jeremy Falcon17-Apr-14 8:57
professionalJeremy Falcon17-Apr-14 8:57 
GeneralFavor for a favor... some good alternatives. Pin
Shaun Harrington11-Aug-06 3:59
Shaun Harrington11-Aug-06 3:59 
GeneralRe: Favor for a favor... some good alternatives. Pin
Jeremy Falcon13-Jan-07 9:29
professionalJeremy Falcon13-Jan-07 9:29 
Questionhow to represent 1000.25 ???? Pin
Renjith Ramachandran10-Jan-05 19:20
Renjith Ramachandran10-Jan-05 19:20 
AnswerRe: how to represent 1000.25 ???? Pin
Jeremy Falcon13-Jan-07 8:29
professionalJeremy Falcon13-Jan-07 8:29 
QuestionCan we have the PHP? Pin
ChinaHorse18-Mar-04 18:19
ChinaHorse18-Mar-04 18:19 
AnswerRe: Can we have the PHP? Pin
Jeremy Falcon19-Mar-04 10:49
professionalJeremy Falcon19-Mar-04 10:49 
GeneralRe: Can we have the PHP? Pin
ChinaHorse21-Mar-04 1:28
ChinaHorse21-Mar-04 1:28 
GeneralRe: Can we have the PHP? Pin
Jeremy Falcon21-Mar-04 4:25
professionalJeremy Falcon21-Mar-04 4:25 
GeneralYes, SSH Pin
ChinaHorse21-Mar-04 23:17
ChinaHorse21-Mar-04 23:17 
GeneralRe: Yes, SSH Pin
Jeremy Falcon23-Jun-04 9:07
professionalJeremy Falcon23-Jun-04 9:07 

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