Article ID: 47756
Article Last Modified on 8/16/2005
APPLIES TO
- Microsoft QuickBasic 4.0
- Microsoft QuickBASIC 4.0b
- Microsoft QuickBasic 4.5 for MS-DOS
- Microsoft BASIC Compiler 6.0
- Microsoft BASIC Compiler 6.0b
- Microsoft BASIC Professional Development System 7.0
- Microsoft BASIC Professional Development System 7.1
This article was previously published under Q47756
SUMMARY
The two programs shown below demonstrate how a C function can return a string to a compiled Basic program.
For Microsoft Basic PDS 7.00 and 7.10, this example applies only to near strings. If you are using far strings (BC /Fs on compile or when using QBX.EXE), you must use the string-manipulation routines supplied with Basic PDS 7.00 and 7.10 (StringAssign, StringRelease, StringAddress, and StringLength). For more information about far strings, see Chapter 13 of "Microsoft Basic 7.0: Programmer's Guide" for versions 7.00 and 7.10.
MORE INFORMATION
For more information about passing other types of parameters between Basic and C and a list of which Basic and C versions are compatible with each other, query in the Microsoft Knowledge Base using the following word:
BAS2C
Code Example
The following Basic program is BSTRF.BAS, which calls the C function and prints out the returned string and its length:
DECLARE FUNCTION CFUNC$ CDECL ()
a$ = CFUNC$
PRINT a$
PRINT len(a$)
The following program is CSTRF.C, which builds a string descriptor that is passed back to the calling Basic program:
#include <string.h>
struct stringdesc
{
int length; /* length of the string */
char *string; /* near pointer to the string */
};
struct stringdesc *std;
char thestring[18]; /* In the medium memory model this */
/* string will be in DGROUP - which */
/* is required for Basic */
struct stringdesc *cfunc()
{
std->length = 18; /* length of the string */
strcpy(thestring, "This is the string");
std->string = thestring;
return(std); /* return pointer to string descriptor */
}
To demonstrate these programs from an .EXE program, compile and link as follows:
BC BSTRF.BAS;
CL /c /AM CSTRF.C;
LINK /NOE BSTRF CSTRF;
BSTRF.EXE produces the following output:
This is the string
18
Additional query words: QuickBas BasicCom
Keywords: KB47756
