compiling a program to run in DOS mode

Question

I write a simple program, to run in DOS mode. Everything works under emulated console in Win XP / Vista / Seven, but not in DOS. The error says: this program caonnot be run in DOS mode. I wonder is that a problem with compiler flags or something bigger.

For programming i use Code::Blocks v 8.02 with such settings for compilation:

-Wall -W -pedantic -pedantic-errors

in Project \ Build options \ Compiler settings

I've tried a clean DOS mode, booting from cd, and also setting up DOS in Virtual Machine. The same error appears.

Should i turn on some more compiler flags ? Some specific 386 / 486 optimizations ?

UPDATE

Ok, i've downloaded, installed and configured DJGPP. Even resolved some problems with libs and includes. Still have two questions.

1) i can't compile a code, which calls _strdate and _strtime, i've double checked the includes, as MSDN says it needs time.h, but still error says: _strdate was not declared in this scope, i even tried to add std::_strdate, but then i have 4, not 2 errors sazing the same

2) the 2nd code is about gotoxy, it looks like that:

#include <windows.h>

void gotoxy(int x, int y)
{
  COORD position;
  position.X = x; position.Y = y;
  SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE), position);
}

error says there is no windows.h, so i've put it in place, but then there are many more errors saying some is missing from windows.h, I SUPPOSE it won't work because this functions is strictly for windows right ? is there any way to write similar gotoxy for DOS ?

UPDATE2

1) solved using time(); instead of _strdate(); and _strtime(); here's the code

time_t rawtime;
struct tm * timeinfo;
char buffer [20];

time ( &rawtime );
timeinfo = localtime ( &rawtime );

strftime (buffer,80,"%Y.%m.%d %H:%M:%S\0",timeinfo);
string myTime(buffer);

It now compiles under DJGPP.

UPDATE3

Still need to solve a code using gotoxy - replaced it with some other code that compiles (under DJGPP).

Thank You all for help. Just learnt some new things about compiling (flags, old IDE's like DJGPP, OpenWatcom) and refreshed memories setting DOS to work :--)

Answer 1

From the sound of things, you're currently compiling a Windows console program. Even though it's a console program, it still needs Windows to run.

To compile a program to run on real DOS, you'll need to find a (probably really old) compiler and (especially) linker that targets DOS and can produce DOS MZ executables. The last Microsoft compiler to target MS-DOS was VC++ 1.52c. If memory serves, Borland continued to target DOS somewhat later, up through something like Broland C++ 5 or so.

I believe if you check the Digital Mars web site, he may still have a C++ compiler available that targets DOS. Otherwise, you're going to be stuck looking for something used and quite old.

Edit: looking at other answers reminded me of DJGPP and OpenWatcom. My apologies for not mentioning them previously.

Be aware that from a C++ viewpoint, Borland and Microsoft are really old compilers -- they don't do namespaces at all, and template support varies from nonexistent in the Microsoft compiler to mediocre in Borland's. DJGPP is basically a DOS extender to which gcc has been ported; the degree to which it's out of date (or modern) will depend on which version of gcc is involved. The Digital Mars compiler is somewhat more modern than the Borland one if I'm not mistaken, but Walter Bright now spends most of his time working on D instead of C++, so the C++ compiler doesn't really compete with gcc, or MSVC, not to mention something like Comeau or Intel that's based on the EDG front-end.

Answer 2

What you're referring to as "emulated console" has nothing to do with emulation or DOS. You probably are still generating 32/64-bit Windows executables, just using console subsystem.

Start by changing your compiler to one capable of generating 16-bit code. I'm pretty sure that OpenWatcom still supports 16-bit MZ target out of box. IIRC DJGPP too, but I'm not sure and don't know if it's still maintained.

Edit: about gotoxy, you could:

1. Use PDCurses and don't care what is uses internally (I think it's INT10, though)
2. Use interrupt 0x10 on your own
3. Write directly to the VGA memory at 0xB8000

I've never actually developed for DOS, so I don't know which method would be considered the best. Third seems to be the fastest one, though.