Summer 2001 Midterm Review

Historical Context

1. Who first used the word "object-oriented" to talk about programming systems?
2. Name a person or company who designed an OO language within the last 20 years.
3. How did ideas in a drawing program influence OO development?
4. Name another programming approach that was popular when OO was first developing, and name a language of the time that exemplified it.

Changed/Update mechanism

OO Theory

1. What is a class? What is an instance?
2. What is the difference between a class and instance method?
3. What is the difference between a class and instance variable?

Design Critique

1. "Here are my CRC cards. This class here is named MapLinkedList and it is a collection of all the Map objects in the system..."
2. "Here is my object ProcessMap. It knows its Map and it does the basic processing needed to get it on my website..."
3. "But everything is controlled here by the MapManager object. No other object processes without confirming it with the MapManager."

Hotel Doors OOA/D

• Each door lock has a connection to a central lock database
• A master key should open any door.
• A customer is given one or more keys that should open the door that she is assigned to
• If a customer loses a key, all the current keys should be made invalid, and only the new keys should be accepted.
• When a customer checks out, all the current keys should be made invalid, and only the new keys should be accepted.

1. Name at least two classes that you would need in the design for this system, and two classes that you might consider but would reject. Give your reasons for rejecting those two classes.
2. On the back of this sheet or on a separate sheet that you attach to the exam (remember, each problem will be graded separately!), draw the CRC cards for this scenario:

A customer gets a card key, takes it to the door, puts it in the door lock which checks if it's valid, then the door opens because it is valid.

Write Smalltalk Code

UML Class Diagramming

• A Student has a name, a student number, a major, and a transcript. A student knows how to change her major, can report her name or student number, and can provide a grade for a given course.
• A Transcript has a collection of course grades. It knows how to add a course grade, and how to look up a grade for a given course.
• A Major has a department name and a list of courses that are required. It only has accessors.
• A Course has a name, and a number of credit hours associated. It knows how to respond with its name.
• A CourseGrade has a course and agrade associated. It has accessors for each.

Analyze Student/Classroom Code

| s c |
c := Classroom new name: 'CS2390'.
s := Student new name: 'Fred'; section: 'a'; number: '123456789'.
c addStudent: s.
s := Student new name: 'Wilma'; section: 'b'; number: '3456789012'.
c addStudent: s.
s := Student new name: 'Barney'; section: 'a'; number: '012345678'.
"...More code here..." 

Reading Code

| anArray aString |
anArray := #('abc' 'def' 'ghi','jkl').
aString := ''.
anArray do: [:each |
aString := aString, each.].
Transcript show: aString.

• What appears on the Transcript ?
• How many times did the body of the do: loop get executed?

| i test |
i := 1.
test := (i < 10).
[test] whileTrue: [Transcript show: 'hello'.
i := i + 1.].

• How many times does hello get printed in this example?

Simulate a Motorcycle

• When the key is inserted into the ignition, the

  key

  object tells the

  engine

  object to

  start

  .
• The engine should then start to run. When the

  engine

  object is running, it prints Putt! to the

  Transcript

  once a second.
• Each time the

  engine

  objects "putts," it sends a message to its

  wheel

  object to

  turn

  .
• When a

  wheel

  object turns, it prints Turn! to the Transcript.

1. What instance variables are you going to need for each of the key, engine, and wheel classes?
2. Write the methods insert for key; start and run for engine; and turn for the wheel.
3. Write whatever accessor methods you need to make the above example work.
4. Write the workspace code that you'd use to create the above scenario

More Drawing in Smalltalk

1. Using Pen, write the code to draw an equilateral triangle.
2. Using the Box class, write the code to draw a pyramid of three boxes.
3. Explain what this code will do:

| joe |
joe := Box new.
30 timesRepeat: [joe turn: 12.]

Analyze Robot Car

• Six wheels A-F (three per side) which can go forward or backward independently. There is a Controller that can also activate all wheels at once.
• Two sets of sensors. Sensors can be on or off.
• An array of twelve distance sensors 1-12 around the perimeter. Distance sensors report distance to nearest obstacle in direction of sensor.
• An array of four light sensors pointed upward and outward: L3, L6, L9, and L12. Light sensors report brightness.
• A solar panel on an axis and motor capable of turning 360 degrees.

• What classes do you need? What service do each need to provide? What attributes do each need to know?
• Where are there generalization-specialization relationships? Where are there part-whole relationships?

Links to this Page

• Reviews last edited on 24 July 2007 at 2:44 pm by balladeer.cc.gatech.edu
• Summer 2001 Announcements last edited on 13 August 2001 at 9:35 pm by user-1120iv2.dsl.mindspring.com
• Fall 2005 Discussion 4 last edited on 6 December 2005 at 3:45 pm by r36h51.res.gatech.edu
• Discussion 4 - Ryan Nigro last edited on 3 October 2005 at 10:56 am by r52h26.res.gatech.edu
• Discussion 4 - Oh Kil Kwon last edited on 9 October 2005 at 4:22 pm by c-24-30-80-132.hsd1.ga.comcast.net
• Discussion 4 - Kevin Adkisson last edited on 10 October 2005 at 1:35 am by adsl-065-007-154-085.sip.asm.bellsouth.net
• Midterm Review last edited on 7 December 2005 at 10:44 pm by frankfort-win.cc.gatech.edu