At compile time, you can set the INCLUDE environment variable to include the directory where the include files reside. Alternatively, you can use the /I compile line switch to point to the include file directory.
Since your SQL Server application must always contain the SQLFRONT.H and SQLDB.H files, defining the DB-Library functions you use is unnecessary. These functions and their proper declarations are already defined in the include file.
You must define an application's target operating system before including the DB-Library header files. Use the following statements at the beginning of all SQL Server applications that use MS-DOS:
#define DBMSDOS
#include <sqlfront.h>
#include <sqldb.h>