In this blog post, we learn how to write a C program to convert a given number to words?. We will write the C program to convert a given number into words. How to display input number in words using loop in C programming. Write a C program to input a number from the user and convert it into words using a loop. Logic to convert a given number to words in C programming.

Example,

Input: 575655
Output: five lakh seventy five thousand six hundred and fifty five


Input: 27
Output: twenty seven


Input: 234677
Output: two lakh thirty four thousand six hundred and seventy seven

C program to convert a given number to words:

Before seeing the program, let see a representation that shows the place value chart for any 9 digits positive integer number.

9  8  7  6  5  4  3  2  1
|  |  |  |  |  |  |  |  |__ ones' place
|  |  |  |  |  |  |  |__ __ tens' place
|  |  |  |  |  |  |__ __ __ hundreds' place
|  |  |  |  |  |__ __ __ __ thousands' place
|  |  |  |  |__ __ __ __ __ tens thousands' place
|  |  |  |__ __ __ __ __ __ hundred thousands' place
|  |  |__ __ __ __ __ __ __ one millions' place
|  |__ __ __ __ __ __ __ __ ten millions' place
|__ __ __ __ __ __ __ __ __ hundred millions' place

The idea is to divide the number into individual digits based on the above place value chart and handle them starting from the most significant digit. The below program will work for any 9 digit number. You can increase the number of digit by changing data types long to unsigned long long int.

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


#define BUF_SIZE 20

// strings at index 0 is not used, it is to make array
// indexing simple
char* one[] = { "", "one ", "two ", "three ", "four ",
                "five ", "six ", "seven ", "eight ",
                "nine ", "ten ", "eleven ", "twelve ",
                "thirteen ", "fourteen ", "fifteen ",
                "sixteen ", "seventeen ", "eighteen ",
                "nineteen "
              };

// strings at index 0 and 1 are not used, they is to
// make array indexing simple
char* ten[] = { "", "", "twenty ", "thirty ", "forty ",
                "fifty ", "sixty ", "seventy ", "eighty ",
                "ninety "
              };

char * numToWords(int n, char* s, char *str, int len)
{
    memset(str,0,len);
    // if n is more than 19, divide it
    if (n > 19)
    {
        strcat(str,ten[n / 10]);
        strcat(str,one[n % 10]);
    }
    else
    {
        strcat(str,one[n]);
    }
    // if n is non-zero
    if (n)
    {
        strcat(str,s);
    }
    return str;
}

// Function to print a given number in words
char* convertToWords(long n, char *out)
{

    char str[BUF_SIZE] = {0};
    // handles digits at ten millions and hundred
    // millions places (if any)

    strcat(out, numToWords((n / 10000000), "crore ",str,BUF_SIZE));


    // handles digits at hundred thousands and one
    // millions places (if any)
    strcat(out, numToWords(((n / 100000) % 100), "lakh ",str,BUF_SIZE));

    // handles digits at thousands and tens thousands
    // places (if any)
    strcat(out, numToWords(((n / 1000) % 100), "thousand ",str,BUF_SIZE));

    // handles digit at hundreds places (if any)
    strcat(out, numToWords(((n / 100) % 10), "hundred ",str,BUF_SIZE));

    //Increase code readability
    if (n > 100 && n % 100)
    {
        strcat(out, "and ");
    }

    // handles digits at ones and tens places (if any)
    strcat(out, numToWords((n % 100), "",str,BUF_SIZE));

    return out;
}

int main()
{
    //Get input number from user
    long num;
    char str[60] = {0};
    
    printf("Enter any number: ");
    scanf("%ld", &num);

    // convert given number in words
    printf( "%s",convertToWords(num,str));

    return 0;
}

Output:

Enter any number: 4567890
forty five lakh sixty seven thousand eight hundred and ninety

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