vocales de minusculas a mayusculas c++

programa qeu pasa de minusculas a mayusculas 

#include "iostream"
#include "stdio.h"
using namespace std;
void MAYUCULUS(char cad [])
{
int i=0;
int des='a'-'A';
while(cad[i]!='\0')
{
if(cad[i]=='a' ||cad[i]=='e'||cad[i]=='i'||cad[i]=='o'||cad[i]=='u')
{
cad[i]=cad[i]-des;
}
i++;
}
}
int main(int )
{
char cad[50000] ;
cout<<"Ingrese Frase:"; cin.getline(cad,100); MAYUCULUS(cad); cout<