Stack

# include <iostream>
using namespace std;


struct stack {
    int top=0;
    int arr[100];

    void push( int num ) {
        if( top<100 ) arr[top++] = num;
        else cout << "Stack Overflow" << endl;
    }

    int pop() {
        if( top ) return arr[--top];
        else {
            cout << "Stack Underflow" << endl;
            return -1;
        }
    }
};

int main() {
    struct stack int_stack;
    int cmd, num;

    cout << "1 - push\n2 - pop\n0 - Quit" << endl;
    while( true ) {
        cout << "cmd: ";
        cin>>cmd;
        if( !cmd ) break;
        switch(cmd) {
        case 1:
            cout << "Push: ";
            cin>> num;
            int_stack.push(num);
            break;
        case 2:
            cout << "Pop: ";
            num = int_stack.pop();
            if( num!=-1 ) cout << num << endl;
            break;
        }
    }
}