1. CPS120: Introduction to Computer Science Lecture 16 Data Structures, OOP & Advanced Strings

2. Pointer Use in C++. A pointer is a variable or constant that holds a memory address a) Hexadecimal numbers are used for representing memory locations 216793 216794216801iptr … 2168013i 216802

3. Using Pointers Pointers must be initialized e.g. iptr =&I; This reads iptr is assigned the address of i

4. Intializing Pointers Declare pointers before use, as with other variables. Each variable being declared as a pointer must be preceded by an asterisk (*). Initialize pointers before use to a 0, NULL or an address to prevent unexpected results

5. Pointer Operators & is the address operator which returns the address of its operand * is the indirection operator or dereferencing operator and returns the value to which the operand (pointer) points. sizeof - used to determine the size of an array during program compiliation

6. Using enum enum allows you to create your own simple data types for special purposes Create a type Give it a name Specify values that are acceptable enum sizes {small, medium, large, jumbo}; The compiler assigns an integer to each enum item

7. typedef typedef gives a new name to an existing data type typedef float real; Confusing to the reader, should be used sparingly

8. Structures Structures group variables together in order to make one's programming task more efficient. Any combination of variables can be combined into one structure. This is a useful and efficient way to store data. struct Student { string socSecNum; string lastName; string firstName; int pointsEarned; double gpa; };

9. Using Structures Each of the different variables are called members of the structure Structures allow us to keep related data referring to individual members together Strings, integer, and floating-point variables may be grouped together into one structure. In effect, we have created our own customized data type. The semicolon after the closing curly brace is required

10. Using the new data structure The structure definition should be placed above the main function of a program but below the compiler directives Declare an actual variable of this programmer-created data type within a function (such as main) in order to make use of this structureDone with a declaration statement like Student freshmen; This reates a variable called freshmen of the data type Student

11. Assigning values to the structure To assign a grade point average (GPA) of 3.4 to the gpa member of the variable freshmen, use the statement: freshmen.gpa = 3.4; The period (.) that is used between the variable name freshmen and the member gpa is called the dot operator. The dot operator simply us to reference individual members of a structure

12. Nested Structures You can use a previously defined structure as a member of another structure Address is nested inside of the Customer structure. Since Address is used within Customer, the structure definition for Address must be placed above Customer in order to avoid compile errors struct Address { string street; string city; string state; int zip; }; struct Customer { string name; string phone; Address homeAddress; Address businessAddress; };

13. CPS120: Introduction to Computer Science Lecture 16B Object-Oriented Concepts

14. The Procedural Paradigm The functions and algorithms are the focus, with data viewed as something for the functions to manipulate

15. Object-Oriented Paradigm Data should be placed inside the objects and that these objects should communicate with each other in the form of messages

16. Classes The definition of an object is know as a class It is similar to using basic data structures in C++ When you declare an object, you are said to have instantiated it (given it instances) Objects are members of a class Paul Millis, George Bush and George Washington being members of the human being class The design of a class is as important as its implementation

17. Including Classes in C++ For classes, the #include directive uses different punctuation for header (.h) files Quotation marks are used when the header file is a source file in the same location as the program source code Angle brackets are used when the header file is one of the compiler's pre- compiled library functions

18. Designing a Class Think in an object-oriented way E.g. an answering machine encapsulates the functions of an answering machine with the data (messages). The buttons are the equivalent of sending messages to the machine

19. Defining a Class Functions and variables that are prototyped and declared in a class definition are called members

20. Public vs Private Private: Cannot be accessed outside the object Public: Can have access to all the variables and functions public: // constructors circle(); // default constructor circle(const circle &); // copy constructor // member functions void SetRadius(float); double Area(); private: // data float radius;

21. Constructors Allow all data encapsulated within an object to be initialized to preset values so that errors can be avoided

22. Member Functions Provide a way for a programmer to pass data to and get data from an object Implemented like a normal C++ function Except -- The class name and the scope- resolution operator (: :) precede the function name circle : : circle() // default constructor

23. OOP Advantages: Reusability Reusability is a major benefit of object- oriented programming

24. OOP Advantages: Containment Containment is a term used to describe an object that contains one or more objects as members (Passes the 'has-a' rule)

25. OOP Advantages: Inheritance Inheritance is the term used to describe an object that inherits properties from another object (Passes the 'is-a' rule) The class from which an object inherits properties is called a parent class or base class The class that inherits the properties is called a child class or derived class

26. CPS120: Introduction to Computer Science Lecture 16C Advanced Strings

27. Library functions manipulate strings length function stringLength = userString.length( ); To compare two strings if (string1 = = string2) Test two strings alphabetically if (string1 < string2) { cout << "string1 comes before string2 alphabetically "; }

28. Library functions manipulate strings To compare two strings if (string1 = = string2)

29. Library functions manipulate strings Test two strings alphabetically if (string1 < string2) { cout << "string1 comes before string2 alphabetically "; }

30. Concatenation To combine two strings into one larger string: name = "John"; lastName = "Doe"; cout << name + lastName; The character array that is going to receive the additional characters must have enough memory allocated to hold the additional characters The STRCAT function will continue to add characters even if it reaches the end of the destination character array The result is that other memory is overwritten with the remaining string data.

31. A String Class A string class can make C++ strings much easier to use a)A string class can provide bounds checking to avoid string errors b)A string class can also allow the use of standard C++ operators when working with strings i)+, =, and = =

32. Converting Strings There are C++ library functions that allow you to convert numbers stored in strings to integer and floating point values atoi-- numbers stored as characters can be converted for calculations atol -- converts a string to a long integer atof -- convers a string to a floating point number

33. Using A String Class Required header file #include "oostring.h"

34. Instantiating a String Object // Instantiate empty string object oostring MyString1; // Initialize while instantiating oostring MyString2("Hello, World!");

35. Assigning Values to Strings MyString1 = MyString2; MyString1 = "string variable"; MyString1 = 'A';