National Instruments PC-OPDIO-16 Manuale Utente

You can find some example programs and project files created in version 3.1

NIDAQWIN\BCCP_EX

 in the directory.  Newer versions can use 3.1 project files.

See Special Considerations in the Creating a Windows Application Using Borland C++ and the
Windows SDK section earlier in this chapter.

    

Buffer Allocation

    

To allocate memory, you can use the Windows functions 

GlobalAlloc()

 and

GlobalFree()

 or an NI-DAQ memory management function, 

NI_DAQ_Mem_Alloc

 or

NI_DAQ_Mem_Free

.  After allocation, to use a buffer of memory, you must lock memory with

GlobalLock()

 or 

NI_DAQ_Mem_Lock

.  After using the memory, you must unlock memory

with 

GlobalUnlock()

 or 

NI_DAQ_Mem_Unlock

.

GlobalAlloc()

GlobalLock()

GlobalPageLock()

     

Huge Buffer Access   

When referencing memory buffers that may exceed 64 KB in size, use huge pointers to reference
the buffer.  Any other pointer type will not perform the correct pointer increment when crossing
the 64 KB segment boundary.  When you use the huge pointer, C automatically adjusts for
segment wraparound and normalizes the segment for pointer comparison.

    

String Passing

    

To pass strings, pass a pointer to the first element of the character array.  Be sure that the string is
null-terminated.

    

Parameter Passing

    

By default, C passes parameters by value.  Remember to pass pointers to the address of a
variable when you need to pass by reference.