The list of similarities between classes and structs is long-structs can implement interfaces, and can have the same kinds of members as classes. Structs differ from classes in several important ways, however: structs are value types rather than reference types, and inheritance is not supported for structs. Struct values are stored "on the stack" or "in-line". Careful programmers can sometimes enhance performance through judicious use of structs. For example, the use of a struct rather than a class for a Point can make a large difference in the number of memory allocations performed at run time. The program below creates and initializes an array of 100 points. With Point implemented as a class, 101 separate objects are instantiated-one for the array and one each for the 100 elements. If Point is instead implemented as a struct, as in only one object is instantiated-the one for the array. The Point instances are allocated in-line within the array. This optimization can be misused. Using structs instead of classes can also make an application run slower or take up more memory, as passing a struct instance by value causes a copy of that struct to be created.