Changing the values of pointers via addresses - c++

Question

This week, we were tasked to create a program where:
Program displays the addresses and values of the array
User inputs the corresponding address he wants to change
User inputs the new value for that address
I was able to figure how a pointer works but it displays another number instead of the inputted value.
Here's the code:
int j =1, var, nx;
int array[4] = {3618, 6555, 5012, 1869};
int* pa; //pointer
char choice;
int remember = 0;
pa = array;
cout << endl;
cout << "\t------------------------" << endl;
cout << "\t\t Values" << endl;
cout << "\t------------------------" << endl;
for(int i = 0; i<4; i++){
cout << "\tarray" << j;
cout << " = " << std::dec << *(pa + i);
cout << " (" << pa + i << ")" << endl;
j++;
}
cout << "\t------------------------" << endl << endl;
cout << "\tPlease enter an address: ";
cin >> hex >>var;
cout << endl;
cout <<"\tYou entered: " << hex << var << endl;
cout << "\tPlease enter a new value: ";
cin >> nx;
pa = (int*)var;
cout << endl;
*pa = nx;
pa = array;
j=1;
cout << endl;
cout << "\t------------------------" << endl;
cout << "\t\t New Values" << endl;
cout << "\t------------------------" << endl;
for(int i = 0; i<4; i++){
cout << "\tarray" << j;
cout << " = " << std::dec << *(pa+i);
cout << " (" << &array[i] << ")" << endl;
j++;
}
cout << "\t------------------------" << endl << endl;

Answer 1

The problem is cin >> nx; is reading the value as hex. I'm quite sure this is happening because the previous use of cin in the program read the value as hex: cin >> hex >>var;. I observed the same thing happening with a cout statement I added to your program when testing it.
If that is changed to cin >> std::dec >> nx;, the behavior of the program is correct.
E.g., using your test run: 353 in hex when converted to decimal is 851.
A helpful tip for future: You don't need the j variable: inside the for loops you can just use i + 1.

Answer 2

What OP is seeing is the the hex modifier still being in effect.
cin >> hex >>var;
turns on hex. Nothing turned it off again.
So when OP types in 353, the program interprets it as a hexadecimal number. 0x353 == 851.
Solution:
Revert to decimal input.
cin >> dec >> nx;

Answer 3

A good habit to get into is to use descriptive words as your variables. It makes it a whole lot easier to debug, and more importantly understand what is going on.
Now, if I'm interpreting this correctly, you are setting pa equal to a new pointer called var, instead of setting pa equal to var. Here is a reference page on pointers, Scroll to the dereference operator to see what I was talking about. The (int*) is unnecessary.