I've seen your previous posts and I bit my tongue, but no more.
As someone who spent the better part of his life and many thousands of dollars studying the intricacies of Computer Programming, if you cannot answer this question yourself, you have no business near C++.
I'm working on an Operating System in C++ in Microsoft Visual Basic 6.0
What on earth does that mean?
1. An Operating System doesn't run on anything but bare metal. It completely controls the computer.
2. C++ in Visual Basic 6.0? That's nonsense. Are you using C++ or Visual Basic? Neither are suitable for a first attempt at an Operating System. Stick to C (and you'll need a good understanding of assembler too) until you are more comfortable with what you are doing.
If you really really use MS-DOS, and not just Command Prompt under Windows: Borland C++ Compiler v5.5 Download
Scroll half a page to get the link. Just keep in mind that this is 20+ years old, with no support (as is MS-DOS itself).