Q27486: CALLing C I/O Routines Does Not Affect QB Cursor Position

Article: Q27486
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom | mspl13_basic
Last Modified: 7-FEB-1990

Problem:

Microsoft C routines (medium model) linked with a compiled BASIC
program that do screen output [such as printf ("hello, world.\n");] do
not update the cursor position after returning to the calling BASIC
program.

For example, after 1) doing a PRINT from BASIC, 2) CALLing a C routine
that does some printf's, and 3) returning to BASIC, the next PRINT
statement goes directly after the last BASIC PRINT statement, ignoring
the \n's (newline characters) from the called C routine.

Response:

This is expected behavior. C routines should not change the BASIC
cursor position. This information applies to Microsoft QuickBASIC
Versions 4.00, 4.00b, and 4.50, to Microsoft BASIC Compiler Versions
6.00 and 6.00b, and to Microsoft BASIC Professional Development System
(PDS) Version 7.00.

To work around this limitation, OPEN "CONS:" as a device in BASIC and
print to the console (screen) using PRINT# or PRINT# USING in BASIC.
This forces BASIC to go through the operating system's console device
instead of using direct writes to video memory.

The following is a code example where a C function doesn't change the
cursor position in BASIC:

   'The following QuickBASIC program prints:
   ' Hello.
   ' Goodbye.t part of this line gets erased.
   DECLARE SUB CRoutine CDECL ()
   CLS
   PRINT "Hello."
   CALL CRoutine
   PRINT "Goodbye."

   /* C program */
   #include <stdio.h>
   void croutine ()
   {
   printf ("The first part of this line gets erased.\n");
   }

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