COP3330 Test 1 Review 1 Intro to Object Oriented Programming Machine languages this is what is necessary for the computer Hard for people 2 Classes and Objects Assembly languages these are symbolic translations of machine code easier Object an encapsulation of data and functions that act upon that data Three to read for people to read aspects of an object Name variable name Attributes member data the data that describes the what the object is Behavior member functions behavior aspects of the object functions that describe what the object does Class a blueprint for objects A class is a user defined type that describes what a certain type of object will look like A class description consists of a declaration and a definition usually split into separate files i e header file An object is a single instance of a class You can create many objects from the same class type Declare A declaration gives an interface A variable declaration gives the type A function declaration tells how to use it without bothering with how it works A class declaration shows what an object will look like and what its available functions are Define A definition usually consists of the implementation details This part doesn t need to be seen by the user of the interface A function definition is the code that makes a function work function body A class definition consists of definitions of its members Use The use of an item through its interface The user of an executable program uses the graphic interface keyboard and mouse The user of a function is a programmer who makes calls to the function without needing to know the implementation details The user of a class is also a programmer who uses the class by creating objects and calling the available functions for those objects Public Can be accessed from inside or outside of the object Essentially the interface of the object The user of an object is some other portion of code Private Can only be used by the object itself A general rule Make member data private to protect it If there are functions that do not need to be part of the interface then these can be private as well Reasons for hiding data Makes interface simpler for user Principle of least privilege More secure Less chance of misuse Class implementation easy to change without affecting other modules that use it To declare a class class ClassName public private public member data and functions go here private member data and functions go here Do not forget the semicolon at the end 3 Constructor A special member function of a class whose purpose is usually to initialize the members of an object You do not explicitly call the constructor function it is automatically called when you declare an object A constructor is easy to recognize because It has the same name as the class It has no return type i Example a Circles circ1 This creates an object named circ1 and causes the Circles constructor function to be run for the circ1 object The scope resolution operator is used for specifying which class a member belongs to when we define it separately from its declaration inside the class The format is className memberName To class a member function of an existing object we use the dot operator The syntax format is objectName memberName memberName can be a member function call or a member data item i Examples a f1 Show f1 is the object Show is the member function b cout f2 Evaluate f2 is the object Evaluate is the member function 4 Constructor with parameters To utilize a constructor with parameters we can pass arguments in when the object is declared Fraction default constructor i ii Fraction int n int d 1 constructor with parameters 5 Default constructor A constructor with no parameters When we declare objects and do not pass in any parameters the default constructor will be used Examples i ii Fraction f1 f2 fraction objects that will use the default constructor iii Examples with parameters Fraction f1 2 3 passes in 2 and 3 as parameters Int x 4 y 8 Fraction f2 x y passes in the values stored in x and y Default parameters can be used with constructors as well The constructor Fraction int n int d 1 has a default parameter of d 1 so if you do Fraction f3 6 the first parameter initializes to 6 and the second one initializes to 1 6 Compilation and Debugging Multiple file projects Most full programs are not contained in a single file A class module normally consists of i A header file Contains the declaration of the class without implementation details Usually in the format filename h ii An implementation file Contains implementations of the class members Usually in the format filename cpp iii Examples a circle h header file for a class called Circle b circle cpp implementation file for Circle class iv Filenames do not have to be the same as the class name but it helps to identify the contents or purpose of a file v include the header files NOT the cpp files Compilation Compile stage and linking stage Compile Stage Syntax checked for correctness i ii Variables and function calls checked to unsure that correct declarations were made and that they match iii Translation into object code Linking Stage Links the object code into an executable program i ii May involve one of more object code files iii The linking stage is the time when function calls are matched up with their definitions and the compiler checks to make sure it has one and only one definition for every function that is called iv The end result of linking is usually an executable program v Examples of linking vi g c frac cpp main cpp translates into object code vii g o sample frac o main o links object code into executable called sample to run this you would simply type in the executable s name 7 Debugging Compile stage errors linking stage errors and run time errors Compile stage errors These are errors that will be reported by the compiler which usually provides a filename and line number indicating where it ran into trouble Always start at the top of the error list Compile as you go Linking stage errors These errors do not usually contain line numbers since the linker works on object code not the original source code Usually caused by agreement between definitions and calls Usually specify a symbol which resembles a function or variable name Run time errors These must be tested while running a fully compiled program To catch fatal errors try to wedge the mistake between extra printout statements to locate the cause To catch logic errors place extra printout