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Standard & Non-standard C++...
The C++ language standard is designed to be portable. Pure standard code will run on any machine (after being compiled for a particular platform). It will run on a simple computer with a text display, a keyboard, and disk storage. So, there are no graphics or VGA in standard C++. Every C++ compiler will have all of the standard headers and the associated standard library functions. (Well, they are not all 100% standard-compliant... but that's another discussion.)
Most beginning C++ textbooks stick-to standard C++, so that the examples will work on any compiler/platform.
This also means that most real-world programs contain some non-standard code. Most compilers will have additional headers & libraries. Every compiler has a different set of additional non-standard headers.
You can check your compiler's documentation for stuff like _AX and geninterrupt. If you don't get any 'hits', then your compiler doesn't have them.
#include <iostream> // Standard
#include <stdlib.h> // Standard, but should use <cstdlib>
#include <dos.h> // Non-standard
#include <mem.h> // Non-standard
#include <stdio.h> // Standard, but should use <cstdio>
#include <conio.h> // Non-standard, but very common