1. A mini TRACS

2. Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
What is printed?

3. Step 1: Draw round all expressions
Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
What is printed?

4. Step 2: Draw arrows to show the order the statements are executed
Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
FALSE
TRUE
What is printed?

5. Step 3: Work through the program showing variables and output
Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
counter
FALSE
TRUE
What is printed?

6. Step 3: Work through the program showing variables and output
Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
counter 1
FALSE
TRUE
What is printed?

7. Step 3: Work through the program showing variables and output
Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
counter 1
FALSE
TRUE 1
TRUE
What is printed?

8. Step 3: Work through the program showing variables and output
Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
counter
counter 1 1
FALSE 2
TRUE
What is printed?
Happy days
Working out area
counter = counter + 1
counter = 1 + 1
counter = 2

9. Step 3: Work through the program showing variables and output
Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
counter 1
FALSE
TRUE 2 2
TRUE
What is printed?
Happy days

10. Step 3: Work through the program showing variables and output
Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
counter
counter 1 1
FALSE 2
TRUE 3
What is printed?
Happy days
Happy days
Working out area
counter = counter + 1
counter = 2 + 1
counter = 3

11. Step 3: Work through the program showing variables and output
Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
counter 1
FALSE
TRUE 3 2
TRUE 3
What is printed?
Happy days
Happy days

12. Step 3: Work through the program showing variables and output
Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
counter
counter 1 1
FALSE 2
TRUE 3 4
What is printed?
Happy days
Happy days
Happy days
Working out area
counter = counter + 1
counter = 3 + 1
counter = 4

13. Step 3: Work through the program showing variables and output
Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
counter
counter 1 1
FALSE
FALSE 4 2
TRUE 3 4
What is printed?
Happy days
Happy days
Happy days

14. Step 3: Work through the program showing variables and output
Variables Table
counter = 1 while counter < 4: print("Happy days") counter = counter + 1 print(“End of program”)
counter
counter 1 1
FALSE
FALSE 2
TRUE 3 4
What is printed?
Happy days
Happy days
Happy days
End of program

15. Now for another example

16. What is printed? (Output)
Variables Table
def input_name(): name = input("What is your name? ") counter = 1 while counter <= 4: print("Hello" + name) counter = counter + 1 print("Goodbye "+ name)
What is printed? (Output)
Working out area
Step 1: Draw round all expressions
Step 2: Draw arrows showing the order in which the statements will be executed
Step 3: Work through the program filling in the variables table and the Output box