1. Types A type consists of –a set of values –a set of operations on those values Types can be –primitive (atomic, non-decomposable) –composite (includes recursive types) Types can be –built-in –user-defined

2. Primitive types Typical primitive types –Boolean = {true,false} –Character = {…,’a’,…’z’,…’0’,…,’9’,…} –Integer = {0, 1, -1, 2, -2, … } –Float = {0.0, …, 1.0, -1.0, …, 3.1415, …} Set of primitive types is language-dependent Value of primitive types typically implementation-dependent, though can be written into language spec (e.g. Java, C#)

3. Gotcha’s Boolean is not always a distinct type –C++ bools are really ints Character is not always a distinct type –C, C++, Java are really just (unsigned) ints Languages sometimes provide many variants on a primitive type: –Java’s Integer types: byte, short, int, long

4. User-defined primitives Enumerations allow programmers to create their own primitive (non- decomposable) types: –C++ enum day {Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday}; Monday prints as 1 –Java enum Day {Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday} Monday prints as Monday methods can be attached to enumerands