C program to convert a digit into words

#include<stdio.h>
#include<conio.h>
#include<string.h>
char *single_digit[]={"","one","two","three","four","five","six","seven","eight","nine"};
char *two_digit[]={"ten","eleven","twelve","thirteen","fourteen","fiveteen","sixteen","seventeen","eighteen","nineteen"};
char *tens_multiple[]={"","","twenty","thirty","fourty","fifty","sixty","seventy","eighty","ninty"};
char *tens_power[]={"hundred","thousand"};
void one(char *num1)
{
 printf("%s",single_digit[*num1-'0']);
}
void two(char *num2)
{
 if(*num2=='0')
 {
  num2=num2+1;
  one(num2);
 }
 else if(*(num2)=='1')
      {
       printf("%s",two_digit[*(num2+1)-'0']);
      }
     else
      {
       printf("%s ",tens_multiple[*num2-'0']);
       num2=num2+1;
       one(num2);
      }
}
void three(char *num3)
{
 if(*num3=='0')
  {
   num3=num3+1;
   two(num3);
  }
 else
  {
   one(num3);
   printf("%s "," hundred");
   num3=num3+1;
   two(num3);
  }
}
void four(char *num4)
{
 if(*num4=='0')
  {
   num4=num4+1;
   three(num4);
  }
 else
  {
   one(num4);
   printf("%s "," thousand");
   num4=num4+1;
   three(num4);
  }
}
void convert(char *number)
{
 //printf("\nNumber is %s length is %d",number,strlen(number));
 while(*number=='0')
  {
   number=number+1;
  }
  //printf("\nnumber is %s length is %d",number,strlen(number));
  int l=strlen(number);
  //printf("\n first number is %s ",single_digit[0]);
  switch(l)
   {
    case 1:
     one(number);
     break;
    case 2:
     two(number);
     break;
    case 3:
     three(number);
     break;
    case 4:
     four(number);
     break;
    default:
     printf("\nOnly four digit numbers are allowed");
    }
}
void main()
 {
  char *num;
  printf("\n Enter a number ");
  scanf("%s",num);
  //printf("String is %s",num);
  convert(num);
  getch();
 }

output
Enter a number 1230
one thousand two hundred thirty