User`s guide

30 Agilent VISA User’s Guide
3 Programming with VISA
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.