>If I Replace the BYTE with STRING in VFP, if get the famous Fatal exception error C00005 !, When i use INTEGER, it works but returns wrong values.
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>Yes the variable names have to be the same as the one in the DLL, it was just a typo.
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>A Variable Type BYTE in VB is i Think an Integer value from 0 to 255, so why is INTEGER dont work in VFP.
>
An INTEGER type in VFP is 32 bits. You might try SHORT (16 bits), but you'll probably get the same results. The reason I suggested a STRING is that a normal (not Unicode) one character string contains 8 bits which is the size of a BYTE. However, VFP may include a null terminator on the string (CHR(0)) which may be causing the problems you're seeing.

BTW, the only time I've see a DLL function call generate a C5 error is when the value that was passed to a function should have been declared and passed by reference, but the declaration and function passed it by value.