1. Week 5 LBSC 690 Information Technology
Programming
Week 5
LBSC 690
Information Technology

2. Software Software models aspects of reality Examples
Input and output represent the state of the world
Software describes how the two are related
Examples
Ballistic computations
Alta Vista
Microsoft Word

3. Types of Software Compilers and interpreters
Application programs (e.g., Powerpoint)
What you normally think of as a ``program’’
Compilers and interpreters
Programs used to write other programs
Operating system (e.g., Windows XP)
Manages display, CPU, memory, disk, tape,
Embedded program (e.g., BIOS)
Permanent software inside some device

4. Discussion Point: The Mythical Person-Month
If it would take one person three months, why does it take four people SIX months?
The original estimate might have been too low
Partitioning strategy led to a long “critical path”
Training new people takes each some time
More people means more communications

5. Training Time Simple Example Learning the specification takes time
Full time person = 2,000 hours/year
Part time person = 288 hours per year
No training  7 part time people
With training  10 part time people
Learning the specification takes time
Learning organizational “rules” takes longer!

6. Communications Sort of like continuous training
Who needs to know what I just learned?
Can be minimized by good partitioning
Limit the number of interfaces
Can be facilitated by computers
Asynchronous communication techniques
, private newsgroups, voice mail

7. Estimating Completion Time
Rules of thumb
1/3 specification
1/6 coding
1/2 test planning, testing, and fixing!
Add time for coding to learn as you go, but don’t take time away from the other parts!
Reread the section on “gutless estimating” if you are tempted

8. Programming Languages
Used to specify every detail of the model
Special purpose
Able to specify an entire class of models
Spreadsheets (Excell, Quatro Pro, ...)
Databases (Access, Paradox, Oracle, ...)
General purpose
Able to specify any possible model
Pascal, C, Java, JavaScript, Perl, ...

9. History of Programming
Machine language
Language that machine can understand
Machine dependent
Zeroes and Ones
Assembly language
Assembler changes names to machine code
High-level languages
Compiler/Interpreter translates to machine language
Machine independent
FORTRAN, COBOL, C, C++, Javascript

10. Machine Language Everything is a binary number For instance
Operations
Data
For instance
might represent “add”
first number to add
second number to add

11. Assembly Language Symbolic instruction codes and addresses
Symbolic instruction code “ADD”
Symbolic address “SUM1”
For instance
ADD , SUM1

12. High level Languages Procedural (modular) Programming
Group instructions into meaningful abstractions
C, Pascal, Perl
Object oriented programming
Group “data” and “methods” into “objects”
Naturally represents responses to events
C++, Java, JavaScript

13. Object Models Represent things in the world as “objects”
Simplest objects are “variables”
Represented with a name (n, teacher, …)
May be assigned a value (n=4, teacher=“Daqing”, …)
Represent actions with “methods”
Simplest methods are “operations”
Represented with a symbol (+, -, *, /, …)
“Classes” group objects with methods
Classes model how kinds of things behave
Objects are instances of classes

14. Data Types Boolean: true/false Numbers: 5, 9, 3.1415926
Strings: “Hello World”
Variables: Temperature, F, Celsius,
Class: Temperature
Instance: CollegeParkTemperature
Method: toCelsius(F)

15. Arrays A set of elements Each element is assigned an index
For example, the number of days in each month
Each element is assigned an index
A number used to refer to that element
For example, x[4] is the fifth element - count from zero
Arrays and loops work naturally togther

16. Operations and Assignments
-x reverse the sign of x (negation)
Add 6 and 5 (numeric)
“Hello” + “World” Concatenate two strings
2.1 * 3 Multiply two values
x++ increase value of x by 1
x = 5 set the value of x to be 5
x += y x = x + y
x *= 5 x = x * 5

17. Comparisons x == y returns true if x and y are equal
x != y returns true if x and y are not equal
x > y returns true if x is greater than y
x <= y returns true if x is smaller than or equal
to y
x && y returns true if both x and y are true
x || y returns true if either x or y is true
!x returns true if x is false

18. toCelsius? Function toCelsius(F) { Celsius = 5/9 * (F-32)
return Celsius }

19. Statements Simple assignment statements
Celsius = 5/9 * (F-32)
Statements that invoke a method
Temperature.toCelsius(104)
Return a value from a method
return Celsius

20. Basic Control Structures
Sequential Control Structure
Conditional Selection Control Structure
Repetition Control Structure

21. Sequential Control Structure
b = 3
c = a * b

22. Conditional Selection Control Structure
if (gender == “male”) {
greeting = “Hello, Sir” }
else {
greeting = “Hello, Madam”

23. Repetition Control Structure
Program Example 1:
n = 1
while ( n <= 10) {
document.writeln(n)
n++ }
Program 2:
For (n = 1; n <= 10; n++) {

24. Programming for the Web
Common Gateway Interface (CGI) [Server side]
Forms encode field values into a URL
CGI passes field values to a Perl program
Program generates a web page as a response
JavaScript [Client-side, interpreted]
Human-readable “source code” sent to the browser
Web browser runs the program
Java applets [Client-side, compiled]
Machine-readable “bytecode” sent to browser

25. What is JavaScript Embedded in html (interpreted), not compiled
To make we pages more interactive
Java Script is NOT Java
Minimal data typing and modularity
No graphics, no formal classes

26. JavaScript <HTML> <HEAD>
<TITLE>My first script</TITLE>
</HEAD>
<BODY BGCOLOR=WHITE>
<H1>
<SCRIPT LANGUAGE=JAVASCRIPT TYPE="TEXT/JAVASCRIPT">
document.write("Hello, world!")
</SCRIPT>
</H1>
</BODY></HTML>
Try it at

27. Handling Events Events: Use event handlers to response events
actions that users perform while visiting the page
Use event handlers to response events
Event handlers triggered by events
Examples of event handlers
onMouseover: the mouse moved over an object
onMouseout: the mouse moved off an object
onClick: the user clicked on an object

28. A Simple rollover.html Click rollover.html
Move mouse over and away the arrow
View source
arrowRed, arrowBlue are variables (“new Image”)
arrowRed.src specifies the value
Event handlers “onMouseover” and “onMouseoff”
Name of the image is defined by NAME = “arrow”
<!– Hide script from old browsers …
If (document.images) { … to test browser function

29. Using Function Repetitive tasks => functions
Load multirollover1.html and multirollover2.html
View sources of the two files
Function chgImg handle changing images for all
Program is shorter and clearer
document.textField equal to document[“textField”]

30. Hands on Point: Adopt a JavaScript Program
Launch a web browser
Internet Explorer would be the best choice
See how it behaves if you are 13 (or 65)
View source and read the program
Save a local copy
Make some changes and see how it works

31. JavaScript and Cookies
cookieName=cookieValue;
expires=expirationDateGMT;
path=URLpath; domain=siteDomain
Combine cookie and javascript can do many things
Set your user name
Read your user name
Use cookies as counters