#include<iostream.h> -- old, do not use
The current header (as of the 1990's) is simply iostream#include<conio.h> -- Non-portable, not standard, do not use void main() -- main() is an int function, not a void. See thisclrscr(); -- Non-portable, not standard, do not use tnt[i]=atoi(take[i]); -- Does atoi() take a single character? Look it up.
If the character is >= '0' and <= '9', it's a digit. To convert a digit to a number, subtract '0'. Each of these character are just special numbers so you can do math on them.