Transcript LECTURE FOR Day 1

Introduction

Introduction of Java

Introduction to Programming
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Course Goals/Objectives

Grading
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Programming Languages
A programming language is a language used to write
instructions for a computer to follow
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Java is one of many programming languages
Features of Java
Platform independent
OOP= Object Oriented Programming
Applications and applets
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Platform Independent
Platform independent: the same program can run on
different computers with different operating systems or
different hardware. (more later)
Here are three different computers each with their own
unique Hardware and Software.
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X86
RISC
PowerPC
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(IBM compatible with Windows)
(common in embedded systems)
(Built by Macintosh)
A program for X86 will not run on a PowerPC
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Programming Languages
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Machine language
Language that a computer can understand directly
Consists of only 0's and 1's
Different computers have different machine languages
Want to write a program in a machine language?
Measure of information:
bit (b): a 0 or 1
byte (B): eight bits
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Examples:
file size: 84KB
internet connection: 2Mbps
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Computer Thinks in Binary
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Binary (base 2) - numbers use 2 digits:
JUST 0 and 1
Decimal (base 10) - numbers use 10 digits: 0
THROUGH 9
Converting numbers:
0 0
5
1 1
6
2 10
7
3 11
8
4 100
9
101
110
10
11
12
13
14
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Measure of Information
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Bit (b; short for binary digit)
 either a 0 or 1
Byte (B)
 1 byte = 8 bits
1
1
1
1
KB = 1024 bytes (2^10)
MB = 1,048,576 bytes (2^20)
GB = 2^30 ~ 10^9
TB
= 2^40 ~ 10^12
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Programming Languages
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Assembly language (low level language)
Using symbolic names for binary codes
Need an assembler to translate an assemblylanguage program to machine code
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Example:
Instruction
JMP 2010
STO 617, 201
JZ0 201
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Machine Language
00100010
10001001
10010010
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Programming Languages
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High-level languages
Closer to a natural language; easy for human beings
to read and write
Two categories:
Compiled
Interpreted
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Programming Languages
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Compiler (is a special SW program)
A program that translates a program in a high-level
language to machine code
Source program (code): program in high-level language
Object program (code): translated machine code version
Compiling a program and running a program are two
different activities
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Interpreter (is a special SW program)
Translates and executes each instruction in the source
program, one at a time
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Programming Languages
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Compiled
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Compile once then
run many times
(faster)
If something
changes, the whole
source must be
Compiled again.
Distribution
problems
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Interpreted
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Since each
instruction is
translated, it’s
slower.
If something
changes, just that
code needs to be
changed.
Distribution not as
hard
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How Does Java Achieve Platform-Independent?
First, a Java program is compiled into an intermediate
code called byte-code
Byte-code is a common language that all computers
should understand
In order to understand this byte code, a computer has
to install a Java Virtual Machine (JVM)
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Then, the byte code is translated into machine code and
executed, one at a time, by Java byte-code interpreter
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Byte-code is platform independent!
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H ig h L e v e l
la n g u a g e
SOURCE CODE
C O M P IL E R fo r
W IN D O W S X 8 6
C O M P IL E R
R IS C
X86
N eeded
O b je c t file s
X86
O B J E C T F IL E
R IS C N e e d e d
O b je c t F ile s
C O M P IL E R
P o w e rP C
P o w e rP C
N eeded
O b je c t F ile s
R IS C
O B J E C T F IL E
P o w e rP C
O B J E C T F IL E
R IS C
P o w e rP C
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X86
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JAVA
S o u rc e C o d e
JAVA
S o u rc e C o d e
JAVA
S o u rc e C o d e
JAVA
C O M P IL E R
W IN D O W S X 8 6
JAVA
C O M P IL E R
R IS C
JAVA
C O M P IL E R
P o w e rP C
JAVA
BYTECO DE
X86
JVM
X86
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R IS C
JVM
P o w e rP C
JVM
R IS C
P o w e rP C
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Java – Pure OOP Language
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To be covered next class
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Java – Applications and Applets
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Java application
Stand-alone program
CUI: console User interface
GUI: Graphical User Interface
Java applet
Run within a web browser
Sent across the Internet and run on a local computer
Byte-code program is sent
Local computer has to have JVM
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History of Java
Developed by James Gosling and his team at Sun Micro-system in
1991
As James Gosling and Henry McGilton (1996) wrote in their white
paper The Java Language Environment,
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"The design requirements of Java are driven by the nature of the
computing environment in which software must be deployed."
Computing environment means: World Wide Web, local area
networks, intranets, embedded systems such as TV set-top boxes,
PDAs, cell-phones, copy machines, and other interconnected devices.
Based on C and C++
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Still changing
1.4.2
1.5.0
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Working with JAVA and JCreator
You could write JAVA programs in a text program like
notepad and compile them in the command line. But this is
not convenient.
JCreator is a program that lets you easily:
Type the JAVA program
Compile the program
Run the program
Debug the program
** It’s a program that helps you build JAVA programs
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Working with JAVA and JCreator
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Programming
A computer program: a sequence of instructions for a
computer to follow to solve a problem
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Programming: the process of creating a computer
program to solve a problem
A computer can do some basic operations well; it
follows instructions well
But it must be told what to do
A human being comes up with the solutions
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How to do programming?----next!
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STEP 1: Understand the requirements
Company Payroll Case Study (from [1])
A small company needs an interactive program to figure its weekly payroll.
The payroll clerk will input data for each employee. The input data includes
employee's pay rate, and the number of hours worked that week.
The program should display the weekly pay for that employee.
The weekly pay is calculated as follows:
 Regular pay equals the pay rate times the number of hours worked,
up to 40 hours.
 If the employee worked more than 40 hours, wage equals regular pay
for 40 hours plus over time pay for hours over 40
 Over time pay equals 1.5 times the pay rate times the overtime hours
These are the requirements!
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Do some examples to get a feel for the problem…note
the logic you take to solve the problem
Example 1: If an employee's hourly pay rate is $30.00,
and he worked 52 hours.
…………………………………………Then he made ____Dollars
Example 2: If an employee's hourly pay is $10.00, and
she worked 36 hours.
…………………………………………Then he made ____Dollars
Example 3: If an employee's hourly pay is $20.00 and he
worked 40 hours.
…………………………………………Then he made ____Dollars
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Analyzing the Problem by looking at
INPUT and OUTPUT
INPUT DATA
Hourly payRate
Hours worked
OUTPUT
RESULTS
Weekly pay
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Step 2) Find an Algorithm for
Calculating Weekly Pay
Repeat the following process for each employee:
1. Get the employee’s hourly payRate
2. Get the hours worked this week
3. Calculate Wage:
If hours worked is more than 40
wage = (40.0 * payRate) + (hours - 40.0) * 1.5 *payRate
Else
wage = hours * payRate
4. Display wage
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An Algorithm
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A set of instructions for solving a problem
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Step-by-step solution
Precise (same input gives same output always)
A computer program is, by definition, an algorithm. But we
usually use algorithm to mean instructions expressed in
English or something like English
Algorithms we've seen:
 Recipe
 Direction
 Manual
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Another Example (from [1])
Procedure to start your car
1.
2.
3.
4.
5.
6.
7.
Insert the key.
Make sure transmission is in Park (or Neutral).
Depress the gas pedal.
Turn the key to the start position.
If the engine starts within six seconds, release the key to the
ignition position.
If the engine doesn't start in six seconds, release the key and gas
peal, wait ten seconds, and repeat Steps 3 through 6, but not more
than five times.
If the car doesn't start, call the garage
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An Exercise
Write an algorithm that gets the price and quantity of an
item bought, and displays the total amount paid for that
item after tax. The tax rate is fixed to be 5%.
To get started, work these:
a)
5 widgets at 12.00 each. How much do you pay?
b)
15 widgets at 2.00 each. How much do you pay?
c)
W widgets at P dollars each. How much do you pay?
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How to Do Programming?
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1) Analyzing the problem: Identifying the input data and the
output results
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2) Developing the solution algorithm
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3) Coding the algorithm using a specific programming language
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4) Testing
Running (executing) your program on the computer, to see if it
produces correct results
If it does not, then you must find out what is wrong with your
program or algorithm and fix (debugging)
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Structured Programming
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Top-down development
Any computer program can be written using only three
basic control structures:
Sequence: a sequence of instructions executed in the
order they're written
Selection: executing different instructions based on
certain conditions
Loop: repeating a set of instructions while certain
conditions are met
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Object-Oriented Programming
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To be covered next class
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Course Goals and Objectives
Describe the development of computer programming and
the main characteristics of Java
Gain an understanding of the fundamentals of objectoriented programming, including classes, objects, creating
objects, and using methods
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Apply top-down and other techniques for algorithmic
problem-solving in designing and writing computer
programs
Apply incremental development techniques in writing
complex programs
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Course Goals and Objectives
Understand and use fundamental programming constructs such as
data types and declarations, assignment statements, variables,
constants, and arithmetic and logical operators
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Understand and apply sequence, selection, and loop control
structures in writing programs to solve common computing problems
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Understand and use pre-defined classes
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Create, compile, and execute Java programs to do the following:
Get input data from the user and display results to the user
Perform simple arithmetic calculations, and string manipulations
Perform different tasks based on user input or results of calculations
(selection)
Repeat tasks (loop)
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Course Goals and Objectives
Document programs effectively
Design and use test data for validating programs
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Grading
Projects (3)
50%
LABS should help complete the projects
Homework including labs (assigned but not graded)
These are the ‘self-test questions’ in text
Quizzes (2)
20%
Short 20 question mc t/f fill-in questions and 1 JAVA code
question.
Final
30%
I’ll give you a sample Final + Answers
Participation counts toward marginal cases
If your on the edge of a grade, I look at the participation
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Miscellaneous
Extra Credit. Short ans: None. 1) I have no ‘extra’ time to
manage extra credit work. 2) Not a good practice as a
student. The intention is good but misdirected.
All military related absences or late assignments are
excusable. You are the one responsible for the learning
the material.
Planned absences should not exceed 25% of the course.
i.e. planned vacation or military exercises should not
exceed 4 classes
Never disappear from class [email protected]
Especially when dropping a course!
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Best Way to Learn Programming?
Quotes from Bill Gates:
the best way to prepare (to be a programmer) is to write
programs, and to study great programs that other people
have written. In my case, I went to the garbage cans at the
Computer Science Center and I fished out listings of their
operating system. You've got to be willing to read other
people's code, then write your own, then have other
people review your code.
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Best Way to do well in class
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Do the HW. Don’t just look at answers
Participate in class
Memorize the basic coding structures
Do the projects well (50% of grade!)
Differentiate the ‘interesting’ from the ‘testable’
Time Management !?!
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Review (1)
High-level
programming language
byte-code
program
interpreter
Java
compiler
source
program
machine language
object
program
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platform
independent
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Review (2)
programming
algorithm
loop
computer
program
sequence
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selection
input and
output
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References
[1] Programming and Problem Solving with C++, 3rd Ed., Nell Dale,
Chip Weems, Mark Headington, pp 33-37.
[2] Structured programming,
http://en.wikipedia.org/wiki/Structured_programming
[3] COMPILERS, INTERPRETERS AND VIRTUAL MACHINES,
http://www.homepages.com.pk/kashman/jvm.htm#_computers
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