C++: Why does getch return -1 before I press any key?

Question

linux

Actually, subject. Here is the code and its output?

#include <stdio.h>
#include <iostream>
#include <curses.h>
#include <ncurses.h>
using namespace std;
int main(){
  int code;
  code = getch();
  std::cout << code;
}

-1

------------------
(program exited with code: 0)
Press return to continue

Answer 1

Pusho needs char , int for numbers only.

Answer 2

do {
   code = getch();
} 
while(code == -1);
std::cout << code;

Answer 3

Mix https://en.cppreference.com/w/cpp/io
with https://en.cppreference.com/w/cpp/io/c
Not good. especially getch() is not a standard.