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UIT2201: CS & the IT Revolution
Tutorial Set 2 (Spring 2013)

(D-Problems discussed on Wednesday, 23-Jan-2013)
(Q-Problems due on Friday, 25-Jan-2013)

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(IMPORTANT NOTE for all Scratch Programs: What is given in the homework writeup is merely the minimum requirement. You are encouraged to use your creativity and imagination to make your Scratch program do MORE than the minimum requirement and, more importantly, to make it FUN.)

Practice Problems: (not graded)
I have included a number of practice problems for you to try out. These problems will help you to "ease into" the materials covered in the course. (If you have difficulties with these practice problems, please quickly see your classmates or the instructor for help.)

T2-PP1: [Your first Scratch program]
After downloading Scratch (See T1), write your first Scratch program that will make the cat (the default sprite/actor) "move around, change customs, and say Meow" a few times.

T2-PP2: [Doing-something-many-times in Scratch program]
After you had fun with your first Scratch program, now is time of get more serious. Instead of just randomly moving around, how about getting the cat to "do something many times", such as doing the following 8 times: (move forward 10 steps; change costume, say "Meow" for 0.5s;)
(Note: You can add the "same commands" 8 times, but there is a simpler way. Find it and use it!)
(If you can't find it, check out T2-D1 first.)

T2-D0: Read [SG] Ch. 1 & 2

T2-D1: [Having fun with Scratch]
After you have downloaded Scratch, you can now download the following simple Scratch programs:
(a) forward-backward.sb -- (Learn how each command works.)
sum-1-to-5-no-loop.sb -- (This Scratch program computes the sum of 1+2+3+4+5. It does it the straightforward way, without using loops! This works, but is not scalable for large sums such as (1+2+3+. . . + 99 + 1000).
sum-1-to-5-loop.sb -- (This Scratch program computes the sum of 1+2+3+4+5. It does it with a loop, like the algorithm in the lecture notes. This works and is scalable for large sums such as (1+2+3+. . . + 99 + 1000).
sum.sb -- (The Scratch program computes sum of 1..100 and is more concise.)

Examine these Scratch programs carefully to see how they work. Make small changes (by modifying the Scratch blocks) and see what happens (you should save as your own versions). You can also play around with the other Scratch blocks to see what they do. Try combining some of the blocks.
Also, try right-clicking the different "objects" to see what other functionalities are available. Try them out to see how they work.

T2-D2: (Algorithm: Step by Step Instruction)
Write out an informal algorithm for going from the Dean's Office of your home faculty to the UIT2201 lecture venue at ERC-SR1.
[Note: Your algorithm should be given in the same format as that the algorithm for "sum of 1 to 100" in lecture notes or like that in Figure 1.1 of [SG3]. You may need to carefully "define" your own "primitive operations".]

T2-D3: (Computing Device)
Consider one computing system that you encounter in your everyday life and that has not been discussed in the lectures (preferably one related to your own discipline). Discuss how it might have been designed and note the similarities and difference with other examples we considered in class.

T2-D4: (All kinds of graphs or networks)
Graph model (also called networks) are used in many different discipline to model all kinds of things. Do a search and find a problem (not from CS-IT-Engg field) that has been modeled and solved as a graph problem.
(Does not have to be graph coloring problem, of course.)

T2-Q1: (15 points) (Cat moving...)
Write a Scratch program that makes the cat do the following:

• Cat to face to the right;
• Cat to start from (0,0), the middle of the "stage".
• Make a 90 degree turn, then say "Ready"
• make a 270 degree turn, then say "Start"
• move 2 steps right; move 5 steps up; then say "Meow" for 0.5sec,
• move 4 steps right; move 5 steps down; then say "Meow" for 0.5sec,
• move 6 steps right; move 5 steps up; then say "Meow" for 0.5sec,
• move 8 steps right; move 5 steps down; then say "Meow" for 0.5sec,
• ... ...
• move 18 steps right; move 5 steps up; then say "Meow" for 0.5sec,
• move 20 steps right; move 5 steps down; then say "Meow" for 0.5sec,
• make a 270 degree turn, then say "... puff, puff" for 1sec; pause for a second;
• make a 90 degree turn, then say "...the END, Thank you" pause for a second;

(IMPORTANT: You WILL LOSE MARKS if your Scratch program do not conform to the standard naming convention.)

(Note: Remember the remark above about minimum requirements and about enhancing your Scratch program with creativity and imagination!.)

T2-Q2: (5 points) (Algorithm Even-Odd-101-to-2013)
In the lecture notes, algorithm Sum-1-to-100 finds the sum of all the integers from 1 to 100, namely, 1 + 2 + 3 + ... + 99 + 100.

Modify this algorithm very slightly to get Algorithm Even-Odd-101-to-2013 that finds the sum of all the odd numbers from 101 to 2013, namely, 101 + 103 + 105 + ... + 2011 + 2013.
(Note: Please make only small changes to the original algorithm.)

T1-Q3: (10 points) [Pervasiveness of Computing Devices in Everyday Life]
(a) Over the next two days, keep track of your activities (say, in 2-3 hour blocks) and record any computing devices that was used in any aspect of the activity. (Do not forget such devices as microwaves and bus card validators.) [Include a one-page attachment of a summary of this log.]
(b) Discuss if and how computing devices have helped make your life more "easy" or "difficult". Please be specific about "easy" and "difficult".
(Note: Be concise and precise -- I am expecting 2-3 pages total (including the 1-page log). .)

A2: [Black and White Colouring]
Give an algorithm that will determine if a given graph can be coloured with two colours, black and white, and, if so, give such a black-and-white colouring.