09)What is the purposes of register used in c++.in c++ help they are used more examples and they are used memory addresses……How can we find the specific functions of memory addresses used in programming?Ex int() and int86() functions…..

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

#define VIDEO 0x10

void movetoxy(int x, int y)
{
union REGS regs;

regs.h.ah=2;
regs.h.dh=y;
regs.h.dl=x;
regs.h.bh=0;
int86(VIDEO,&regs,&regs);
}

void main ( )
{
clrscr();
movetoxy(35,10);
cout<<”Hello”;
getch();
}

at the start defined a constant with 0x10 I ask what is the purpose of that 0x10 what is the purpose of the address?
Is that a memory address? how we get to know about a task of a given memory address as a programmer? is there documentations? Is there where to find these things…?