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Scratch Programming. Lesson 4 Question asking and answering. We are going to learn…. How to ask a question and receiving answer First touch of variable – answer Creating variables How to use If….. Else loop…. Forever IF vs. If Broadcast. Question asking and receiving answer. - PowerPoint PPT Presentation
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Scratch ProgrammingLesson 4Question asking and answering
We are going to learn…
•How to ask a question and receiving answer
•First touch of variable – answer•Creating variables•How to use If….. Else loop….•Forever IF vs. If•Broadcast
Question asking and receiving answer
Input answer here
The answer will be stored in the “answer” variable
Variable
•What is variable?•A storage location of some value or words• is a variable•When we ask more than one question, the
latest one will over-write the previous one•More variables are needed for storage
Creating variablesClick here to create a new variable
This box will pop-out and name should be given to the variable
Choose the target user of the variable
How to use variable
To control whether the variable will be displayed on the stage
Give a value to the variable
Change the value of a variable by a certain number
Operators (Part I)Addition, Subtraction, Multiplication and Division
Smaller than, equal to OR greater than
String- a sequence of charactersString functions, 1) Join two strings together2) Select one letter from the string depending on the position of the letter3) Return the length of the string
If… else
•If the operation in returns a TRUE value, the commands here will start to run.
•If the operation in returns a FALSE value, the commands inserted here will start to run.
Forever If vs. If• Forever If
▫ Non-stop to check the condition
• If▫ Just check the condition
once
Forever If vs. If
• Once the green flag is pressed▫ Would play meow sound
whenever the mouse point to the sprite
• Would play meow sound only when the mouse point at the time and the green flag is pressed at the same time
Broadcast
• Generate a message to the program
• Set an object ( actor / background) to response when a message is broadcast by others
How to use Broadcast
The sprite gives a broadcast signal: change
The stage changes to another background when receive the “change” signal
Task of the lesson• Start a new program• In this program, the sprite can help you calculate 3
questions• The green flag will be the program starter• Input:
▫ Tell the user that you are going to help them in▫ Allow the user to input 2 numbers, one by one
• Output:▫ Return “Correct!” if you have the correct answer and
change to another background with a background music▫ Return “Wrong!, the answer is ___” to return the correct
answer to the user▫ The outputs will be displayed 2-3 seconds
• Save your program and upload as Program4_3_ _ _ in eclass