Well, it calculates, it just won't loop, or exit right. . .

I've tried a lot of things, I just don't know why it won't work right. So please help me.

When I make Exit '5' instead of 'E' it works, but it says, "Press any key to continue." I have tried the 'while' loop, but when I do it I get a black screen. I don't know why it's not working, so please help me with this.Code:#include <iostream> int addition ( int x, int y ) { return x + y; } int subtraction ( int x, int y ) { return x - y; } int multiplication ( int x, int y ) { return x * y; } int division ( int x, int y ) { return x / y; } using namespace std; int add(); int sub(); int mul(); int div(); int main() { int input, z; z = 0; do { cout<<"1. Add\n2. Subtract\n3. Multiply\n4. Divide\nE. Exit\nEnter your choice: "; cin>> input; switch ( input ) { case 1: add(); break; case 2: sub(); break; case 3: mul(); break; case 4: div(); break; case 'E': ( z + 1 ); break; default: cout<<"Error: Unknown Input\n"; break; } return 0; } while ( z != 1 ); } int sub(){ int x, y; cout<<"Enter the first number to subtract: "; cin>> x; cin.ignore(); cout<<"Enter the second number to subtract: "; cin>> y; cin.ignore(); cout<<"The difference is: "<<subtraction ( x , y ); cout<<"\n"; return 0; } int add(){ int x, y; cout<<"Enter the first number to add: "; cin>> x; cin.ignore(); cout<<"Enter the second number to add: "; cin>> y; cin.ignore(); cout<<"The sum is: "<<addition ( x, y ); cout<<"\n"; return 0; } int mul(){ int x, y; cout<<"Enter the first number to be multiplied: "; cin>> x; cin.ignore(); cout<<"Enter the second number to be multiplied: "; cin>> y; cin.ignore(); cout<<"The product is: "<<multiplication ( x, y ); cout<<"\n"; return 0; } int div(){ int x, y; cout<<"Enter the first number to be divided: "; cin>> x; cin.ignore(); cout<<"Enter the second number to be divided: "; cin>> y; cin.ignore(); cout<<"The quotiant is: "<<division ( x, y ); cout<<"\n"; return 0; }