CS midterm

Question 1

algorithm

Answer 1

• Specific set of instructions for carrying out a procedure or for solving a problem (anything trying to solve)
• Must produce a result
• Must be achievable/possible
• Must be expressed clearly

Question 2

algorithms typically (qualities)

Answer 2

Algorithms typically…
•	Make some assumptions
•	Have multiple solutions
•	Include decisions
•	Are expressed in modular pieces

Question 3

is ordering Chinese take-out an algorithm?

Answer 3

yes

Question 4

computer algorithm

Answer 4

“An algorithm is a well-ordered collection of unambiguous and effectively computable operations that when executed produces result and halts in a finite amount of time.”

1. Algorithms are well ordered
2. Have unambiguous operations
3. Effectively computable operations
4. Produce a result
5. Finish in a finite amount of time

Question 5

programming errors

Answer 5

• Syntax Errors – spelled words wrong
• Runtime Errors – program error that occurs when program is running
• Logic Errors – something wrong with logic, produces the wrong output

Question 6

specify a location

Answer 6

• point(x, y)

* line x1, y1, x2, y2)

Question 7

function call statement

Answer 7

• point(40, 77); = statement
• Point = function name
• (40, 77) = arguments
• ; = terminator

Question 8

Coding Style when Calling Functions

Answer 8

• One space after commas in function arguments
• No space between function name and opening bracket
• No space before the semicolon at the end of a statement
• No space after opening bracket or before closing bracket
• point(10, 20);

Question 9

shapes

Answer 9

• triangle(x1, y1, x2, y2, x3, y3);
• 6 arguments
• quad(x1, y1, x2, y2, x3, y3, x4, y4);
• 8 arguments
• rect(x, y, width, height)
• ellipse(x, y, width, height)
• point xy in middle
• eg. ellipse(50, 50, 15, 15);

Question 10

commenting code

Answer 10

• Code comments provide information that is not otherwise available from reading from the code
• Often a message to your “future self”
• // comment

Question 11

bezier curves

Answer 11

•

bezier(x1, y1, cx1, cy1, cx2, cy2, x2, y2)

• eg. bezier(10, 10, 90, 20, 30, 80, 90, 90);

Question 12

attributes

Answer 12

• Eg. Once you set strokeWeight to 10, everything you draw after will have a strokeWeight of 10 until you change it again
• Order matters (Sequential Control flow)
• CMD + t will format code correctly

•	size();
o	changes size of drawing
•	noStroke();
o	no border
•	noFill();
o	nothing in the middle

Question 13

stroke weight

Answer 13

•	strokeWeight(weight);
o	Effects everything that comes after the code
•	strokeJoin(join);
o	join = BEVEL, MITER, or ROUND
•	strokeCap(cap);
o	cap = SQUARE, PROJECT, or ROUND
o	Project extends stroke

Question 14

color

Answer 14

• Additive (“mixing all colours makes white”)
• RGB – used to specify colour on computer displays
• HSB – used to describe colour
• Subtractive (“mixing al colours makes black”);
• CMY/CMYK – common in printing

Question 15

active code

Answer 15

change things actively (draw)

Question 16

functions

Answer 16

•	Code that is “packaged” so it can be run “by name”
•	Often performs some computation and returns a value (but not always)
•	We used functions all the time in Processing…
o	noFill();
o	ellipse(75, 50, 23, 52);

Question 17

function defintion

Answer 17

•	void draw() {
•	ellipse(moouseX, mouseY, 30, 30);
•	}
o	void = function return type
o	draw = function name
o	() function parameters
o	{} code block

Question 18

active vs static mode

Answer 18

• We have been writing code in static mode:
o Our drawing is only shown when the program finishes
o There is no user input
o We can’t define any functions
• From now on, we’re using active mode:
• “active mode” is also called “dynamic mode”
o People can interact with our program
o Drawings can be “updated” to make animation
o We can define functions
o With setup() and draw() functions

Question 19

set up

Answer 19

• void setup() {
• size(200, 200);
• backround(255); // white
• noStroke();
• }

Question 20

static mode

Answer 20

• size(200, 200);

* ellipse(mouseX, mouseY, 30, 30);

Question 21

active mode

Answer 21

• void setup() {
• size(200, 200);
• }
• void draw() {
• ellipse(mouseX, mouseY, 30, 30);
• }

Question 22

other functions

frame rate

Answer 22

•	frameRate(1); // 1 frame per second
o	Draws very slow
•	printLn(“setup”)
o	Prints lines in the bottom of Processing in Console
o	Used to find errors

Question 23

event

Answer 23

• An observable occurance, phenomenon, or an extraordinary occurrence
• A message to notify an application that something happened
• Ex. Keyboard (key press, key release), Mouse Events (button press, button release, moved)

Question 24

setup and draw are events

Answer 24

•	The setup event happens when the program is first run
o	setup() is a built-in function that represents this event
•	The draw event happens 60 times per second (by default)
o	draw() is a built-in function that represents this event

Question 25

mousePressed event

Answer 25

• A mousePressed event happens when a mouse button is pressed/touch pad tapped
o void mousePressed() {
o }
• Also a mouseReleased event

Question 26

keyPressed event

Answer 26

• A keyPressed event happens when a key is pressed
o void keyPressed() {
o }
• Also a keyReleased event

Question 27

variables

Answer 27

• Symbolic name used to reference an “unknown” value
• Value may change, but the symbolic name doesn’t
• Kinds of Variables:
o Built-in variables (eg. mouseX, width)
o Constants (CENTER, BEVEL)
o User defined variables

Question 28

useful processing built in variables

Answer 28

•	Mouse X, mouse Y
•	pmouseX, pmouseY (p = previous)
•	width, height
•	frameCount, framerate
•	key, keyCode
•	mouseButton
o	keyPressed, mousePressed
o	NOTE: different than the event functions with the same names!!!!