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http://www.java2s.com/Code/C/Data-Type/Convertanintegertowords.htm

Please refer Programming interviews exposed.
I feel it has a cleaner and simpler implementation

oops... please ignore the prev comment...
I did not read the question correctly...

write a function which will print under hundred i.e 0-99 then pass the number two digit then one digit then two digit then one digit into a stack .. when this is done pop them and pass them to printUpToHundred() function which will do the printing stuff and in the main you print lakh,then thousand then hundres take care of the case 1lakh and 2lakhs also

write 4 functions.
Unit
Tens
Hundreds
Thousands

Give the input to the thousands. it does a division by 1000 and gets the top 2 numbers and prints it. then it passes the number% 1000 to the hundreds which does likewise till it reaches the units with then prints the units.

0 is also a special case.
1-19 are special case
tenth place- define all(20,30,40...90)
hundredth place- define all(100,200...)
thousandth place- define all(1000,2000,...)
if(num==0)write zero
else...
{
use the above data stored to display the num.
special case... 'dont display zeroes'.
e.g. 1024- one thousand, twenty, four
e.g. 2318- two thousand, three hundred eighteen.
}

#include <stdio.h>
#include <string.h>

void main()
{
char *unit_words[] = {"zero", "one","two","three","four","five","six","seven","eight","nine"};
char *teen_words[] = {"ten", "eleven","twelve","thirteen","fourteen","fifteen","sixteen","seventeen","eighteen","nineteen"};
char *ten_words[] = {"error", "error","twenty","thirty","forty","fifty","sixty","seventy","eighty","ninety"};
char hundred[] = " hundred";
char and[] = " and ";
char value_str[50] = "";
int value = 0; /* Integer to be converted */
int digits[] = {0,0,0}; /* Stores digits of value entered */
int i = 0;

printf("Enter an integer less than 1000: ");
scanf("%d",&value);
if(value>=1000)
value =999;
else if(value<1)
value = 1;

while(value>0)
{
digits[i++] = value%10;
value /= 10;
}

if(digits[2] > 0)
{
strcat(strcat(value_str,unit_words[digits[2]]), hundred);
if(digits[1] >0 || digits[0] > 0)
strcat(value_str, and);
}
if(digits[1] > 0)
{
if(digits[1] == 1)
strcat(value_str,teen_words[digits[0]]);
else
{
strcat(value_str,ten_words[digits[1]]);
if(digits[0] > 0)
strcat(strcat(value_str, " "), unit_words[digits[0]]);
}
}
else
if(digits[0] > 0)
strcat(value_str, unit_words[digits[0]]);
printf("\n%s\n", value_str);
}