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.
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Chapter 1
What is Programming?
Lecture Slides to AccompanyAn Introduction to Computer Science Using Java (2nd Edition)
by
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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
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Definitions
* program — a set of directions telling a computer exactly what to do * programming languages — languages for specifying sequences of directions to a computer ¢ algorithm— a sequence of language independent steps which
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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
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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
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Central Input processing | ` Main c— keyboard
unit memory camera
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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
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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
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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,
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prog1.java — JAVA 01110100 01101000 01001011
Programmer types program using a fext editor File is stored on disk with type “JAVA.” Text is represented in binary Java compiler runs in CPU
prog1.java prog1.class
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Running Your Own Java
Program
Enter the program source code in a data file using an editor
Transform the source program into machine language or Java Bytecode using an compiler (e.g Javac)
Use an interpreter to execute the compiled program (e.g Java)
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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
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Java
¢ applications — stand-alone programs that run on you own computer — can read and write data on your disk disk ¢ applets— 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