Tonight we will look at:

1
Lecture 5

• Tonight we will look at
• Function Overloading
• Dynamic Data Allocation
• Abstract Data Types (ADT)
• Introduction to Object Orientation

2
Function Overloading

• In C, one can reuse a function name with
  different input parameters.
• Let's look at lect5_1.cpp and lect5_2.cpp
• Reasons for overloading
• Less "namespace polution"
• Easier for user to understand
• Very useful when using "classes"
• Rules
• parameter list must be different in type and/or
  number of parameters

3
Dynamic Memory Allocation

• When writing a program that is either time or
  space constrained it may be useful to create
  variables only when needed.
• Up until now, memory allocation has been static,
  that is at compile time.
• With dynamic memory allocation techniques, data
  space can be allocated as needed during run-time.
• Created on heap or free-store.
• Downside, need to deallocate space. Failure to do
  so creates "memory leak".

4
Dynamic Memory Management

• To allocate memory
• In C
• new operator
• In C
• malloc function (and its associated functions)
• To de-allocate memory
• In C
• delete operator
• In C
• free function
• We will use the new and delete operators

5
Syntax

• new returns a pointer to the type of storage
  allocated
• type pointerVarName new type
• int p new int
• delete takes the pointer variable name
• can be equal to NULL - be careful
• delete p
• Let's look at lect5_3.cpp

6
What is Abstraction?

• A view that separates the areas of concern from a
  whole, to make an item easier to comprehend and
  manage.
• For example, an automobile has an abstraction
  layer that allows us to drive almost any type of
  vehicle.
• Areas of concern
• Accelerator, Brakes, Steering Wheel, Ignition,
  Gear Shift, Wind Shield Wipers, Heater, Radio,
  Fuel Gauge, Fuel Filler Cap Location
• Areas of little or no concern
• Engine Technology, brand of vehicle, style of
  wheels

7
Types of Abstraction For Computer Science

• Control Abstraction
• Separates the logical properties of an action
  from its implementation.
• The basis of functional decomposition.
• Data Abstraction
• Separates a data type's logical properties from
  its implementation.
• Built-in for simple types
• Simple variables and operators
• Custom Type composed of data and functions
  specific to operate on that data

8
ADT Continued

• ADT encapsulates both attributes (data) and
  methods (functions) that operate on that data
  into a single entity.
• A struct in C contains only a data collection.
• A class in C is an abstract data type

9
C ADT Is The Class

• Let's look at a simple C class specification
  (myTime.h)

10
ADT Operations or Method Types

• Constructor
• A class method that creates an instance of a
  class
• Transformer
• A class method that changes the value of a class
  attribute
• Observer
• A class method that returns the value of a class
  attribute
• Iterator
• A class method that processes the components of
  an ADT, one at a time.

11
Class Specification

• Separate the What from the How
• Public
• Interface exposed to user
• Private
• Items hidden from user
• Information hiding
• User only sees what needs to be known to use
  class
• Protects internals of class from user
• Can change implementation transparently

12
Class Implementation

• Normally A Class is defined in two files.
• The Specification File
• className.h
• The Implementation File
• includes specification file
• className.cpp
• Use of the the Scope Resolution Operator
• The user will include the class.h file, class
  .cpp file (or .o) and generate a separate .cpp
  file to utilize the class.
• Let's look at myTime.cpp

13
Utilizing the Class

• Creating a class instance
• called a class object or simply an object
• Let's look at lect5_4.cpp
• A class is a specification of an interface and an
  implementation of the interface
• An object is an instance of the class.

14
Accessing Class Members

• Externally, the class public members of the class
  are accessed using dot notation, somewhat like
  accessing structure members.
• instanceName.classMember
• true for all public members
• functions
• data (if any)
• Internally, you do not use dot notation, just the
  member name.
• Let's continue looking at lect5_4.cpp

15
Constructor

• Classes may contain a special function member
  called a constructor. An implicit one is created
  for you, if you do not explicitly specify one.
• The constructor is called after the user makes a
  call to create an object, but before control
  returns to the user.
• Allows for initialization of class specific
  information.
• Looks like a normal function call, but has name
  of class, and does not have a return type.
• Let's look at lect 5_5.cpp

16
Destructor

• A C Class also provides the facility for an
  optional destructor method.
• Allows for cleanup just before class goes out of
  scope.
• There is an implicit destructor created for you
  if you don't specify one yourself.
• Syntax
• className() body

17
Class Operations

• Two built-in operations are allowed with classes.
• Dot operator
• And assignment operator
• Does a shallow assignment
• C provides a copy constructor to customize
  copies to be deep copies.
• Copy Constructor Syntax
• className( const className classObjectName)