User`s guide

Programming with VISA 3
Agilent VISA User’s Guide 33
Using Sessions
This section shows how to use VISA sessions, including:
• Including the VISA Declarations File (C/C++)
• Adding the visa32.bas File (Visual Basic)
• Opening a Session to a Resource
• Addressing a Session
• Closing a Session
• Searching for Resources
Including the VISA Declarations File (C/C++)
For C and C++ programs, you must include the visa.h
header file at the beginning of every file that contains VISA
function calls:
#include "visa.h"
This header file contains the VISA function prototypes and
the definitions for all VISA constants and error codes. The
visa.h header file also includes the visatype.h header
file.
The visatype.h header file defines most of the VISA types.
The VISA types are used throughout VISA to specify data
types used in the functions. For example, the
viOpenDefaultRM function requires a pointer to a parameter
of type ViSession. If you find ViSession in the visatype.h
header file, you will find that ViSession is eventually typed
as an unsigned long. VISA types are also listed in VISA
System Information in the VISA Online Help.
Adding the visa32.bas File (Visual Basic)
You must add the visa32.bas Basic module file to your
Visual Basic project. The visa32.bas file contains the VISA
function prototypes and definitions for all VISA constants
and error codes.