How to use it. 1  Open Excel & VBA editor 2  (+) Insert the code below under Sheet1. 3  Go back to Excel and select your desired range to fill with random & non-repeating numbers.  Execute the macro (+)
See also What are the rules about using an underscore in a C++ identifier; a lot of the same rules apply to both C and C++, though the embedded double-underscore rule is in C++ only, as mentioned at the top of this answer. Names with double leading underscores are reserved for use by the implementation.
Integer overflow. Overflow is a phenomenon where operations on 2 numbers exceeds the maximum (or goes below the minimum) value the data type can have. Usually it is thought that integral types are very large and people don't take into account the fact that sum of two numbers can be larger than the range.