What does getch () do in C++? code example

Example 1: getch c++ library

#include<iostream.h>
#include<conio.h>

void main()
{
int a=10, b=20;
int sum=0;
clrscr();  // use clrscr() after variable declaration
sum=a+b;
cout<<"Sum: "<<sum;
getch();
}

Example 2: getch() c++

#include <conio.h>
int getch();