Convert integer to roman numeral in C

gistfile1.txt

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

  static int oneThousand = 1000;
  static int fiveHundred = 500;
  static int oneHundred = 100;
  static int fifty = 50;
  static int ten = 10;
  static int five = 5;

  static char numFour[] = "IV";

  char *singlesChars(int tens) {
    switch (tens) {
      case 1:
        return "I";
      case 2:
        return "II";
      case 3:
        return "III";
      case 4:
        return "IV";
      case 5:
        return "V";
      case 6:
        return "VI";
      case 7:
        return "VII";
      case 8:
        return "VIII";
      case 9:
        return "IX";
      case 10:
        return "";//"X";
    }
    return "";
  }
    
  char *tensChars(int tens) {
    //X, XX, XXX, XL, L, LX, LXX, LXXX, XC, C    
    switch (tens) {
        case 1:
          return "X";
        case 2:
          return "XX";
        case 3:
          return "XXX";
        case 4:
          return "XL";
        case 5:
          return "L";
        case 6:
          return "LX";
        case 7:
          return "LXX";
        case 8:
          return "LXXX";
        case 9:
          return "XC";
        case 10:
          return "";//"C";
      }
      return "";
    }
 
  char *hundredsChars(int hundreds) {
    //C, CC, CCC, CD, D, DC, DCC, DCCC, CM, M
    switch (hundreds) {
      case 1:
        return "C";
      case 2:
        return "CC";
      case 3:
        return "CCD";
      case 4:
        return "CD"; 
      case 5:
        return "D";
      case 6:
        return "DC";
      case 7:
        return "DCC";
      case 8:
        return "DCCC";
      case 9:
        return "CM";
      case 10:
        return ""; //"M";
    }
    return "";
  }

  char *thousandsChars(int thousandars, int parentar) {
    int difference = parentar - thousandars*1000;
   
    
    int memSize = 0;
    int listCount = thousandars;
    
    char thousands[thousandars];
    int startingIndex = 0;

    if (difference >= 100) {
      thousands[0] = *"C";
      startingIndex = 1;
    }

    for (int i = startingIndex; i < listCount; i++) {
      thousands[i] = *"M";
    }
    
    return thousands;
  }

  void convertIntToNumerals(int number) {
    
    int thousands = 0;
    int hundreds = 0;
    int tens = 0;
    int remainder = 0;
    
    int subtractnumber = number;

    if (number >= 1000) {
      thousands = number / 1000;
      subtractnumber -= thousands*1000;
    } 

    if (subtractnumber >= 100) {
      hundreds = subtractnumber / 100;
      subtractnumber -= hundreds*100;
    }

    if (subtractnumber >= 10) {
      tens = subtractnumber/10;
      subtractnumber -= tens*10;
    }
 
    if (subtractnumber > 0) {
      remainder = subtractnumber;   
    }

    int difference = number - thousands*1000;
       
    int memSize = 0;
    int listCount = thousands;
    

    int thousandsUnits = difference >= 100 ? thousands + 1: thousands;   
    char thousandsChars[thousandsUnits];
    int startingIndex = 0;

    if (difference == 900) {
      thousandsChars[0] = *"C";
      startingIndex = 1;
      listCount += 1;
    }   

    for (int i = startingIndex; i < listCount; i++) {
      thousandsChars[i] = *"M";
    }   
 
    char *hundredsCharacters = hundredsChars(hundreds);
    char *tensCharacters = tensChars(tens); 
    char *singlesCharacters = singlesChars(remainder);

    int hundredsLength = strlen(hundredsCharacters);
    int tensLength = strlen(tensCharacters);
    int singlesLength = strlen(singlesCharacters);

    int numberChars = hundredsLength + tensLength + singlesLength + listCount;

    char newString[numberChars];
  
    int count = 0;

    for (int i = 0; i < strlen(thousandsChars); i++) {
      newString[count] = thousandsChars[i];
      count += 1;
    }
  
    for (int i = 0; i < hundredsLength; i++) {
        newString[count] = hundredsCharacters[i];
        count += 1;
    } 

    for (int i = 0; i < tensLength; i++) {
      newString[count] = tensCharacters[i];
      count += 1;
    }

    for (int i = 0; i < singlesLength; i++) {
      newString[count] = singlesCharacters[i];
    }
   
    printf("%s\n", newString);
  }

  int main(int argc, char *argv[]) {
    convertIntToNumerals(atoi(argv[1]));
  }