OPP programming

iam designing a menu driven program and want to call a function
when chosen a selection. My function contains two parameters
of type char array and of type int array. Could any1 help me here...?should i call it in main or can i call it in a switch statement or either....?. I have another question also

i have a parrallel array one of each type char and int
and want the user to input a specific character e.g a roman numeral and have the equivalent value in the int array.My menu driven fragment of code is a do while loop.....also with the parrallel arrays i want to be able to add the values of array type int, should i creat another array and use assigning techniques or
shouldnt i use another array at all?. If you are able to help me , could you please give me an example... to give me an idea of what your talking about... would be much appreciated.#iclude < iostream.h>

#include <stdlib.h>
#include <string.h >
#include <iomanip.h>

const int MAXCHARS = 16;
const int MAXVALS = 81;
void menu (char);
void assign3 ( int [], int []) ;

int main ()
{
char roman[MAXCHARS];
int tot_value [MAXVALS];
int array3[MAXVALS];
char choice; menu (choice);
// function call void assign (int, int );
return 0;
}
void menu (char choice)
{
do
{
// This is the menu displayed to the screen
cout <<setw(10) << " The KMA Menu " << endl;
cout <<setw(10)<< "============================"<<endl;
cout << "1. Help\n";
cout << "2. Convert to Arabic\n";
cout << "3. Exit\n";
// This read the user selection
cout << " Enter your choice : ";
cin choice ;
// This selection acts on the user selection.
switch (choice)
{ case '1' : cout <<< " Back to Instruction screen\n";
break;
case '2' : cout <<< " Function process. Convert to arabic\n";
void assign ( int , int ) ; // want to call this function but cant?
break;
case '3' : exit (0);
default : cout <<setw(12) <<" Invalid number. Enter numbers between 1-3"; break;
}
} while (1);
}
void assign (int roman [], int array3 [])
{
int i;
for (i=0; i< MAXCHARS ; i ++ )
cout <<" Enter a roman numeral:";
cin>> roman[i] ;
int j;
for ( j=0 ; j<MAXVALS;j++ )
switch (i)
{
case 'M' : array3[j] = 1000;
case 'D' : array3 [j] = 500;
case 'C' : array3 [j] = 100;
case 'L' : array3 [j] = 50;
case 'X' : array3 [j] = 10;
case 'V' : array3 [j] = 5;
case 'I' : array3 [j] = 1;
default : cout << " Invalid roman numeral. Please re-enter Roman numeral.\n";
break;
return (i);
}
}
}

sorri bout the indentation......