C Object Oriented Programming Jim Allert Introduction

C++: Object Oriented Programming Jim Allert

Introduction z. Instructor: Jim Allert z. Email: jallert@d. umn. edu z. Phone: y 726 -7194 z. Office: Heller Hall 324 A z. Hours: 10: 00 -12: 00 MWF zwww. d. umn. edu/~jallert

Registration and Waiting Lists z. Waiting list priorities set by CSE z. See me after class if you are interested in a override

Today z. Course goals and prerequisites z. Syllabus and logistics z. C++: Larger picture and motivation z. C++: the kernel language

Course Goals z. Change the way you think y. OOP different from traditional procedural model z. Learning the C++ constructs ywhy and when use a construct ywhen not to use a construct z. C++ syntax ythe easiest

You Will Not. . . z. Become an expert C++ programmer y. A starting point for further study z. Learn all the features of C++ y. C++ is a very complex language z. Learn advanced OOP techniques z. Become expert at object-oriented design y. Read a book on Software Engineering

Expected Background z. C programming skills y. Control structures y. Pointers (linked lists) z. No object-oriented experience necessary z. Experience with: y. Turbo C/C++ ydevelopment environment

Syllabus z. Textbooks and on-line resources yplease read assigned chapter(s) before lecture z. Assignments and Exams z. Group work not allowed. z. UMD computer accounts and facilities

Communication z. Email is the preferred medium z. Problems with homework assignments, etc. 1. Contact TA 2. Contact me z. Problems with TA or TA explanations y. Contact me

Outline: the Big Picture z. History of programming languages z. Approaches to Program Design z. Overview of object-oriented programming concepts z. Object-oriented programming and C++

History of Programming Languages z pre-mid-1950’s y machine and assembly language y “ad hoc” data representation and control z 1960’s y Fortran, Cobol, Algol y arrays, control structures y Simula 67, forerunner of C++ z 1970’s y C, Pascal y block program structure, structured control y stepwise refinement

History of Programming Languages z Early 80’s y Modula-2, Ada y modules, Abstract Data Types (ADT’s) z 1980’s: “Classic” OOP y C++, Smalltalk y inheritance, polymorphism z 1990’s: y C++, Java y templates, iterators, exceptions, interfaces

Approaches to Program Design z Stepwise refinement y. Based on the operations performed y. General operations iteratively decomposed into specific ones z Object-oriented design y. Problem decomposed into real-world objects y. Objects have a well-defined interface y. Focus on behavior and collaboration of objects

Structure Chart Boxes z. Example: getting from UMD to Metro. Dome z. Algorithm: Subtask 1: Get in car at parking lot … Subtask 2: Drive to Minneapolis Subtask 3: Find Metro. Dome Subtask 4: Get out of car

Developing an Algorithm (cont) z. Strategy (cont): repetitively divide tasks until each task is easily solved z. Example: Subtask 2 - Drive to Minneapolis 2. 1 Drive east to I 35 2. 2 Drive south to I 35 W 2. 3 Drive south to Minneapolis z. Each division of a task is a “stepwise refinement”

Stepwise Refinement z. Do stepwise refinement until all tasks easy z. Example: 2. 1 - Drive east to I 35 2. 1. 1 2. 1. 2 2. 1. 3 2. 1. 4 Exit parking lot to East Turn right on Woodland Turn left on 21 st Enter I 35 z. This process is know as Top-Down Design

Multi-layer Structure Chart

Another Example Problem: Balance checkbook Top-level tasks 1. Get information 2. Perform computations 3. Print results

Pseudo-code Example 1. Get information 1. 1 Get starting balance 1. 2 Get transaction type 1. 3 Get transaction amount 2. Perform computations 2. 1 IF deposit THEN add to balance ELSE subtract from balance 3. Print results 3. 1 Print starting balance 3. 2. Print transaction 3. 2. 1 Print transaction type 3. 2. 2 Print transaction amount 3. 3 Print ending balance

Motivation for OO approach z. More transparent mapping between: requirements, design, and implementation yeasier verification and validation z. Lower software maintenance costs ydanger of “ripple effect” reduced z. Better code reuse yreuse by “tweaking” can be avoided

Bank account object design Bank Account balance get_balance() deposit(amount) withdraw(amount) Data portion Functions

OOP broad overview 1. Define bank account object a. Data members b. Member functions 2. Program a. Instantiate a bank account object b. Use bank account object i. e. Bank_account my_checking; my_checking. deposit(500); cout << my_checking. get_balance(); my_checking. withdraw(100); cout << my_checking. get_balance();

Manufacturers, Clients, Users z. Manufacturers build objects z. Clients use objects in programs yclient code uses objects you make available through your class definitions. z. Users use programs z. We are interested in object manufacturers and clients here

OOProgramming: Concepts z. Abstraction z. Encapsulation z. Objects and Classes z. Inheritance z. Polymorphism z. Dynamic binding

Abstraction z. Separate: yessential qualities from incidental ones z. Behavior is essential z. Implementation is incidental z. Example: an interface to a vending machine as its abstraction yessential behavior: dispensing products yincidental implementation: the actual products

Encapsulation z. Explicit boundary between abstraction and implementation z. Encapsulation of all essential characteristics of the object z. Frees developers to change implementation ylist processing using arrays ylist processing using linked lists z. Protects clients from using unstable code

Objects and Classes z. Object yidentifiable component in problem domain z. Class y. Abstract Data Type (ADT): state + operations (services)

Example z. House: an Object ydata state: xkitchen_lights, data: on/off xroom_temperature, data: degrees yservices: xturn_on(kitchen_lights) xadjust_thermostat(-5) z. House blueprint: a Class

Inheritance z. Object Single. Family. House is a kind of object House z. Inherits all state and services z. Adds new ones z. Reuse and extend code

Polymorphism z. Polymorphism y. Objects of related types can be used interchangeably y. Can always use a specialized object where a generic one is allowed y. Example: appraising a house xgeneric appraisal form applied to specific homes • • appraise(rambler); appraise(log_home); appraise(townhouse); appraise(colonial);

Dynamic Binding z. Dynamic binding y. Object methods selected at run time y. Or: interface matched with implementation at run-time

OOP Concepts Recap z. Abstraction z. Encapsulation z. Objects and Classes z. Inheritance z. Polymorphism z. Dynamic binding Object-based programming (Ada) Object-oriented programming (C++, Java)

Motivation: why C++ for OOP? z. Large user community yhigh-quality compilers and development tools for many platforms ylearning aids: books, conferences, newsgroup, seminars, consultants z. Multi-paradigm language y. Procedural: better C, Object-based y. Object-oriented z. Legacy code: (mostly) backward compatible with C

C++ Language Evolution z. Simula (Norway, late 60 -s) z. Bjarne Stroustrup, Bell Labs, early 80’s z. Complex simulation software z“C with classes” z. C++ yfeatures and complexity increased with time ywe are lucky - ANSI standard created yand vendors are supporting it

C++ Distinguishing Characteristics z. Strong static type checking z“Manual” memory management yno automatic garbage collection z. Supports multiple programming models yprocedural and object-oriented z. Multiple inheritance z. Operator overloading