Convert int lower or upper case..

#include<iostream.h>
#include<conio.h>
#include<ctype.h>
void main()
{
clrscr();
char ch,a,b;
cout<<"enter any alphabet in upper or lower case: ";
cin>>ch;
if(islower(ch))
{
a=toupper(ch);
cout<<a;
}
else if(isupper(ch))
{
b=tolower(ch);
cout<<b;
}
getch();
}