Need Help For C Functions

pls help me. can i get the function for converting roman numeral to decimal ?? plss ? urgently needed . here is the code :

Code:

#include<stdio.h>
#include<conio.h>
void input(int *num1,int *num2);
void addition(int num1,int num2,int *sum);
void subtraction(int num1,int num2,int *diff);
void division(int num1,int num2,int *quot);
void multiplication(int num1,int num2,int *prod);
void modulus(int num1,int num2,int *mod);
void main()
{int x=0,y=0;
int sum,diff,quot,prod,mod;
char choice;
char again1;
clrscr(); do{ clrscr();
gotoxy(25,1);
textcolor(YELLOW);
printf("************************************");
gotoxy(25,3);
printf("* MENU *");
gotoxy(25,6);
printf("************************************");
gotoxy(25,9);
printf("* (+) ADDITION *");
gotoxy(25,11);
printf("* (-) SUBTRACTION *");
gotoxy(25,13);
printf("* (/) DIVISION *");
gotoxy(25,15);
printf("* (*) MULTIPLICATION *");
gotoxy(25,17);
printf("* (%) MODULUS *");
gotoxy(25,19);
printf("************************************");
gotoxy(25,21);
printf("PLEASE ENTER YOUR CHOICE:");
scanf("%s",&choice);
clrscr();
input(&x,&y);
switch(choice){
case '+':clrscr();
addition(x,y,&sum);
gotoxy(36,10);
printf("SUM:%d",sum);
gotoxy(15,18);
printf("press Y or y if you want to go back from the menu:");
scanf("%s",&again1);
break;
case '-':clrscr();
subtraction(x,y,&diff);
gotoxy(36,10);
printf("DIFFERENCE:%d",diff);
gotoxy(15,18);
printf("press Y or y if you want to go back from the menu:");
scanf("%s",&again1);
break;
case '/':clrscr();
division(x,y,&quot);
gotoxy(36,10);
printf("QUOTIENT:%d",quot);
gotoxy(15,18);
printf("press Y or y if you want to go back from the menu:");
scanf("%s",&again1);
break;
case '*':clrscr();
multiplication(x,y,&prod);
gotoxy(36,10);
printf("PRODUCT:%d",prod);
gotoxy(15,18);
printf("press Y or y if you want to go back from the menu:");
scanf("%s",&again1);
break;
case '%':clrscr();
modulus(x,y,&mod);
gotoxy(36,10);
printf("MODULUS:%d",mod);
gotoxy(15,18);
printf("pres Y or y if you want to go back from the menu:");
scanf("%s",&again1);
break;
default:clrscr();gotoxy(33,10); printf("ERROR IN CODE"); } }
while(again1=='Y'||again1=='y');
getch();
}
void input(int *num1,int *num2)
{gotoxy(25,5);
int xx;
int yy;
printf("ENTER THE FIRST NUMBER:");
scanf("%d",&xx);gotoxy(25,7);
printf("ENTER THE SECOND NUMBER:");
scanf("%d",&yy);
*num1=xx;
*num2=yy;
}
void addition(int num1,int num2,int *sum)
{*sum=num1+num2;}
void subtraction(int num1,int num2,int *difference)
{*difference=num1-num2;}
void division(int num1,int num2,int *quotient)
{*quotient=num1/num2;}
void multiplication(int num1,int num2,int *product)
{*product=num1*num2;}
void modulus(int num1,int num2,int *modulu)
{*modulu=num1%num2;}