If you are using Borland's compiler, you might want to check out bios.h . This library some functions that deal with the DOS serial ports, e.g. bioscom, _bios_serialcom. You will have to watch closely since most bios functions will NOT work under Windows, esp. Win9X & NT.

Essentially, you are going to define some settings such as:

#define COM1 0
#define DATA-READY 0x100

then you will set up a setting that you will pass to the bios call:

#define SETTINGS (_COM_1200 ¦ _COM_CHR7 ¦ _COM_STOP1 ¦ _COM_NOPARITY)
or
#define SETTINGS (0x80 ¦ 0x02 ¦ 0x00 ¦ 0x00)

Which bios call you use will determine how you set up the settings. (You will need to see your online documentation for better examples.)

_bios_serialcom(_COM_INIT, COM1, SETTINGS);
or
bioscom(0, SETTINGS, COM1);

For Windows 9X or NT, you cannot access the bios directly, so you have to go through something like a virtual driver.

If your assignment is for the "or DOS" part, this will help, otherwise, you'll need more/better help than I just supplied.

The following example uses the BuildCommDCB and SetCommState functions (Windows API calls) to set up COM1 at 9600 baud, no parity, 8 data bits, and 1 stop bit. These instructions are by no means complete; ie: variables haven't been declared, etc.



idComDev = OpenComm("COM1", 1024, 128);
if (idComDev < 0) {
ShowError(idComDev, "OpenComm");
return 0;
}

err = BuildCommDCB("COM1:9600,n,8,1", &dcb);
if (err < 0) {
ShowError(err, "BuildCommDCB");
return 0;
}

err = SetCommState(&dcb);
if (err < 0) {
ShowError(err, "SetCommState");
return 0;
}

Let me know if you need more detailed info.