Idea 3of 23Builds onCode is exact steps in order
A variable holds one number
Where does code keep the number it is working on?
Today you'll discover
- what a variable is
- how ADD and SUBTRACT change it
- what SET does to it
Think firstYour game piece moves by code
The variable square starts empty. What does square hold right after the line ADD 4?
Decide first, then press Next. Watch the number in the box after each line.
Five blocks of code: SET 0, ADD 6, ADD 4, SUBTRACT 3, OUTPUT, beside a box named square. As an arrow moves down the code, the box holds 0, then 6, then 10, then 7, and a table records each line and the number after it. OUTPUT shows 7. The last step asks about SET 20, ADD 5, SET 3, ADD 1.
See the whole ideathe big idea and the key word, in one place
The big idea
A variable is a named box that holds one value; each line can change it.
The box, line by line
square holds 0, then 6, then 10, then 7. Only the newest number is kept.
- SET 00
- ADD 66
- ADD 410
- SUBTRACT 37
Easy to get wrongSET and ADD are different. ADD 3 makes the number 3 bigger; SET 3 makes the number exactly 3, whatever it was.
Key words
- variable
- a named box in code that holds one number, which the code can change
- value
- the number a variable holds right now
Ready to use it?
- Track a variable's value through each line of code.