why no worky?

[mynameisben]

hi! i just started programming and am taking a class, im wondering if you could help me understand why this if statement crashes the program. i include some lines from top of program since maybe it has something to do with it.

#include <iostream>
#include <cctype>
#include <string>
using namespace std;
char* C_type = new char[100]; // create array to store types
int* KWH_used = new int[100]; // create array to store kwh used


cout << "How many kilowatt hours did this customer use? ";
cin >> KWH_used[x];
if ( isalpha(KWH_used[x]) ) //why no worky?
//if (KWH_used[x] > 5000) (im using this currently to work)
cout << "Sorry that is not valid input.(DELETING CUSTOMER TYPE)" << endl;
else
x++;

[Zaita]

Don't use cin >>
http://www.cplusplus.com/forum/articles/6046/

The code snippet you've posted is ok. What ranges do you have X going to?

[mynameisben]

x starts at 0 and increases up to array size. i forgot to mention that the program crashes when the user enters a letter at cin >> KWH_used[x]

numbers work fine. so maybe its crashing before if statement. ill look at that link to see if it helps.

[Zaita]

That link perfectly identifies and solves your problem :)