For any of several reasons.
VB may be using a float type rather than a double, your code snippet doesn't include the data types. Is F2A a float or a double? In standard C, pow is a function of type double.
Your floating point constant 123.132 ... can be represented exactly by IEEE 754 double type but it likely exceeds the precision of a double type when you multiply it and square it.
The term 2^100.415 is almost certainly not represented exactly in IEEE 754 double format.
decimal precision of IEEE 754 double type is 15.95 decimal digits.
Expression evaluation order could be different between the two languages.
Could also depend on which CVI compiler you use - native CVI, the new one in latest CVI, Intel, Visual Studio - all of these will work with CVI and all may well produce slightly different results.
I'd tend to believe the CVI result to be more precise.
You could try compiling it on a machine that supports long double or double extended or "quadruple" precision and get a more accurate result. Or use an arbitrary precision package like Maple (or hack it in C# or Java with arbitrary precision class) and see what the "true" result should be.
