Lecture An introduction to computer science using java (2nd Edition): Chapter 1 - S.N. Kamin, D. Mickunas, E. Reingold

Chapter 1 - What is programming? In this chapter we will: demonstrate some problem-solving techniques needed in programming, design an algorithm to solve a problem, write a program to implement an algorithm, discuss the importance of object-oriented programming, discuss some basics of computer hardware, describe the process of entering and running Java programs.

Chapter 1

What is Programming?

Lecture Slides to Accompany

An Introduction to Computer Science

Using Java (2nd Edition)

by

S.N Kamin, D Mickunas, E Reingold

Chapter Preview

In this chapter we will:

¢ demonstrate some problem-solving techniques

needed in programming

¢ design an algorithm to solve a problem

¢ write a program to implement an algorithm

¢ discuss the importance of object-oriented

programming

* discuss some basics of computer hardware

¢ describe the process of entering and running Java programs

— a sequence of language independent steps which

may be followed to solve a problem

Final Maze Solving Program

Object-Oriented Programming

A modern programming paradigm that allows the programmer to model a problem in a real- world fashion

Objects interact with each other by sending

messages

An object is an instance of a class

A class implements an interface and specifies the behavior of an object

Object-Oriented Programming

and Java

¢ The use of OOP in Java Is pervasive

— easy to create multiple objects of the same type

— easy to create similar objects without having to rewrite the overlapping code

¢ OOP makes programs easier to understand and more reliable

¢ Prevents objects from having to Know any more about structure of other objects than Is really necessary

processing | ` Main c— keyboard

unit memory camera

(CPU) CD-ROM drive

Running a Program

First the program and all its data is copied from the hard disk into main memory

The CPU goes to the location of the program

Instruction and reads that word

The CPU determines what action is requested by decoding its bit pattern representation

The CPU performs the action

The CPU then moves to the location of the next

program instruction in memory, reads the word, and

repeats the process

Data Representation

¢ Computers use binary numbers

¢ Numbers can be used to represent any type

of data

— pictures are represented by dividing them into picture elements known as pixels

— video images or animations are represented by

placing several picture one after another

— sounds are represented by sampling the wave at regular intervals

e All data are stored tn files on the hard disk

00001000

00000100 IIIIITIIT0O E=> IIIIIIII= 8,4, 254, 255, 254, 8, 4

Animation is represented as a sequence of pictures Each picture is a sequence of numbers First

picture: 0, 0, 0, 128, 0, 0, 0; Second picture: 0, 0, 128, 192, 128, 0, 0; Third picture: 0, 128, 192, 224,

192, 128, 0 Place two numbers at beginning, giving height and width of each picture: 7, 8, 0, 0, 0, 128,

0Ú; 0,.0,,0,0, 128, 192, 128; 0; 05 +0

Running Your Own Java

Use an interpreter to execute the compiled

program (e.g Java)

Return to the editor to correct any errors (or bugs) and start the cycle again

Errors

Debugging \s the process of detecting and fixing errors found in a program

Syntactic errors are caused by giving the

compiler a program It cannot recognize

Logical errors come from programs that compile correctly but fail to execute as expected

Programs must be designed carefully and

tested thoroughly to ensure that neither error

will occur

— executed from within a browser window (e.g

Netscape or Internet Explorer)

— can be loaded from the World Wide Web and

executed on another computer

— cannot read or write data on your hard disk