Why is #define bad and what is the proper substitute?

Question

#define dItemName        L\"CellPhone\"

Answer 1

Because preprocessor macros, which you've just made, pollute every name scope. They are available everywhere and do not follow standard naming scope rules. Thus, with a macro like that, code like int dItemName = 5; instead gets f'ed over by the preprocessor to instead be int L"CellPhone" = 5;. A constant, global variable would not do this.

All other issues aside, this is IMNSHO the worse issue with macro definitions.