Inline Assembly with Borland/Embarcadero - c++

Question

A quick question here:
I'm trying to experiment with inline assembly using Embarcadero C++ Builder XE3 on 32-bit Windows 7, specifically to start re-teaching myself assembly with the possibility of future pragmatic application.
So far I've been able to write a set of instructions within a simple console project which compiles fine using all C++ Builder syntax at my disposal:
int _tmain(int argc, _TCHAR* argv[]) {
_asm{
mov dl, 0x24
mov ah, 2 // Print character
int 0x21 // Dos Interrupt - Run operation in AH
mov dl, 0x25
mov ah, 2 // Print character
int 0x21 // Dos Interrupt - Run operation in AH
mov dl, 0x26
mov ah, 2 // Print character
int 0x21 // Dos Interrupt - Run operation in AH
mov dl, 0x27
mov ah, 2 // Print character
int 0x21 // Dos Interrupt - Run operation in AH
int 0x20 // terminate COM
}
return 0;
}
This compiles ok, and these instructions work straight in NASM and the Windows native DEBUG environment. What I expect is a simple write to the console: $%&' followed by a successful termination.
However, when I try to run Project1.exe via the command line I immediately get a standard Win7 runtime error popup which disappears after a few seconds and terminates the program.
Running with debugging, I seem to be successfully reaching the first int 0x21 before it hangs, at which point Borland gives me the message:
Project Project1.exe raised exception class $C00000005 with message 'access violation at 0x00401213: read of address 0xffffffff'.
My theory is that I'm not properly initializing the segment with a 256-byte offset (NASM would use something like org 0x100 at the beginning of the instruction set). But I'm not entirely sure that's the issue.
Any ideas?

Answer 1

Those int 0x21 instructions are for MS-DOS and not Windows. They mean something else in a Windows program, with the result that you go up in flames.

Answer 2

I work primarily in C++ Builder, But I've also programmed assembly and nasm for production code (mainly on micros). My recommendation is not to go near C++ builder for anything you don't have to. Learning can be an art and the way you go about learning has a lot to do with the outcome. C++ Builder integration with assembly is a detour through South Compton. Even though it may not be the way you normally work, it will pay off big time to learn nasm in pure command line.