Practice set: specifications, algorithms, traces and tests

P1. Which is a specification?

• Return the earliest date in the list
• Compare each date and keep the earlier
• Use a loop
• Write it in Python

P2. An algorithm must be:

• Finite and unambiguous
• Long and detailed
• Fast and short
• Written in code

P3. Trace “largest so far” on 2, 7, 5, 9. What is the output?

• 9
• 7
• 5
• 23

P4. Trace a running total from 0 on 1, 2, 3, 4. What is the output?

• 10
• 4
• 6
• 24

P5. Which test best checks a method that returns the smallest number?

• A list with the smallest item last
• A list of one item only
• A list already sorted
• A very short list of equal items only

P6. A method starts the largest at 0. For -4, -2, -9 it returns:

• 0, which is wrong
• -2, which is right
• -4
• -9

P7. What does a trace table help you do?

• See how each stored value changes
• Make the program faster
• Avoid writing a specification
• Choose a colour

P8. The average of an empty list is a problem because:

• The count is 0 and you cannot divide by 0
• There is nothing to add
• Lists must have three items
• Averages are always whole numbers