When designing composite types, we should assign each field a type. Oftentimes, we don't really care exactly what those types are, as long as the type provides the functionality that we want.
A classic example would be numeric types. The concept of numbers is simple: basically the same as we were taught in elementary school. In practice, many numeric types are implemented in computer systems because of the different physical storage and representations of data.
By default, Julia ships with the following numeric types; concrete types are darker:
Do you remember when we designed a composite type to represent ...
