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