Reference TypesIn Solidity, some types are very simple so that when you use them (such as declaring variables, calling functions, etc), they are just copied. These types include int, uint, bool, address, and they are usually called value types. On contrast, when you use other complicated types (sturct, array, mapping), you must be carefully to make sure that if you are creating a reference to it, or you are copying it from one data location to another. A reference is the same as a pointer in ...