Static vs dynamic type checking in C++

Question

I want to know what are static and dynamic type checking and the differences between them.

Answer 1

Static type checking means that type checking occurs at compile time. No type information is used at runtime in that case.

Dynamic type checking occurs when type information is used at runtime. C++ uses a mechanism called RTTI (runtime type information) to implement this. The most common example where RTTI is used is the dynamic_cast operator which allows downcasting of polymorphic types:

// assuming that Circle derives from Shape...
Shape *shape = new Circle(50);
Circle *circle = dynamic_cast<Circle*> shape;

Furthermore, you can use the typeid operator to find out about the runtime type of objects. For example, you can use it to check whether the shape in the example is a circle or a rectangle. Here is some further information.