What's the difference between Viread in VC and VB？

[xiaochouyu]

In VB,the  "VISA32.DLL" Declare is

Declare Function viRead Lib "VISA32.DLL" Alias "#256" (ByVal vi As Integer, ByVal Buffer As String, ByVal count As Integer, ByRef retCount As Integer) As Integer

and use like 

viread（vi ,String,count ,retCount ）

In VC，

#include <visa.h>

and use like 

  viRead(vi, (UCHAR *)buf(), bufSize, &actual);

Buffer in VB is a String，but in VC is a  Integer array.

Why？

[KevinTovson]

It may be related to language differences and how data transfer is optimized in the respective languages. For instance, if the buffer can be sent as either a string or integer array but VB handles strings better, strings will be used. Is there a specific reason that this information is required for your application?

[xiaochouyu]

thank you

 I use 

 status = viRead(vi, strRes, 4096, retCount)

 the result only 18 bytes, do you know why？

[KevinTovson]

If you haven't yet, I would take a look at the examples for VISA reads for VC and VB. There are also examples that install when you install drivers on your computer.

Example VISA Message-Based Application

NI-DAQmx, NI-VISA, and NI-488.2 Visual C++ Example Locations