U4L2_3

Use the image to predict what will appear in the Debug Console after the downButton is clicked twice.

• 73 F

  23 C

  71 F

  22 C

• 73

  23

  71

  22

• 23

  73

  22

  71

• nothing or not enough information

Answer explanation

the first time the downButton is clicked the tempF variable becomes 73, the tempC value is calculated to 23, the tempC value appears in the Debug Console (23), and then the tempF value populates the Debug Console

repeat with 2nd click of down button

What will appear in the Debug Console when you run this program?

• 23

  73

• 75

  24

• 73

  23

• nothing or not enough information

Answer explanation

the Debug Console is only updated in the onEvent if/when the down button is clicked. Until the button is clicked, nothing will appear in the Debug Console.

Predict what will appear in the Debug Console when the upButton is clicked.

• 71

• 76

• 77

• nothing or not enough information

Answer explanation

There is no onEvent for the upButton in this snippet, therefore there is not enough information to determine what, if anything, will appear in the Debug Console.

A _________ is a debugging tool that allows you to see your variables update while the program runs, making it easier to see what they are doing.

Answer explanation

WATCHER

You can add watchers for any variable or object property by typing the name of a variable in the box and clicking the blue "add" button. If your program isn't running or the variable hasn't yet been assigned a value, the watcher will report a value of undefined. This isn't an error, it just means that the variable hasn't yet been assigned a value.

What does this command do in a code?

• captures data entered by the user, by reading data from a textInput() screen element

• retrieves a string from within the code

• connects to a helpful messaging app that keeps you connected with the people who matter most

• I don't know

Answer explanation

getText() captures data entered into the App by the user, by reading data from a screen element such as a textInput(), button(), or textLabel().

Which is an example of concatenation?

• a very persuasive and persistent feline

• setProperty("dollarsLabel",

  "text",

  "$")

• onEvent("addOneButton",

  "click",

  function()

• userName = "Hi, "

  +

  getText("nameInput")

  +

  " !"

Answer explanation

In formal language theory and computer programming, string concatenation is the operation of joining character strings end-to-end. For example, the concatenation of "snow" and "ball" is "snowball".

Which of the following is an example of a "counter pattern"?

• onEvent("upButton",

  "click",

  function(){

  temp = 70

• onEvent("upButton",

  "click",

  function(){

  temp = temp + 2

• onEvent("upButton",

  "click",

  function(){

  counter

• onEvent("upButton",

  "click",

  function(){

  pattern 123123...

Answer explanation

in this example every time the upButton is clicked, the value stored in the temp variable (plastic baggie) is replaced with a number that is two more than the previous number. therefore each time the button is clicked, the variable is updating as though it is COUNTING by 2

The only difference between these two lines of code are the " " and some spaces, but they tell the computer to do two very different things. Explain.

Answer explanation

"My favorite number is" is a STRING therefore whatever is in the " " will appear exactly as written in the Debug Console (with the " ").

The second line does not have " " which suggests that myFavoriteNumber is a variable that has been assigned earlier in the code. The computer will identify the value being stored in this variable and populate the Debug console with that value

What are the rule(s) of naming variables?

• cannot contain spaces

• cannot start with an uppercase letter

• cannot contain numbers

• cannot start with a number

Answer explanation

Variable names must:

start with a letter;

contain no spaces.

Variable names may contain numbers (just not as the first character) and may start with a uppercase letter although the convention is to start with a lowercase letter and to use camelCase

what does \n tell the computer to do?

• displays an n in the Debug Console

• turns a positive value into a negative

• resets a variable to zero (nill)

• breaks up a string so that it appears on different lines

Answer explanation

\n separates text by creating a NEWLINE.

With early computers, this ASCII code was created to represent a new line because all text was on one line.

** notice the difference between \ and /...

\ is known as a BACKSLASH and is found in the upper right hand corner of your keyboard

/ is known as a SLASH, forward slash, or stroke (on the ? key) this will return an error if typed in place of \t-hand corner of your keyboard