Program to Convert lower case to upper

#include <iostream>
#include <conio.h>
using namespace std;

int main()
{
 //Program to Convert lower case to upper
 int num;
 char ch;
 cout<<"press any letter either upper or lower =";
 cin>>ch;
 num=ch;
 if(num>=65&&num<=90)
 {
  num=num+32;
  ch=num;
  cout<<"the lower case of your letter is ="<<ch;
 }else if(num>=96&&num<=122)
 {
  num=num-32;
  ch=num;
  cout<<"the upper case letter is ="<<ch;
 }else
 cout<<"your input in invalid please try again";

getch();
    return 0;
 
}