Programming Essentials in Scratch: Unit Exam A
Algorithms, sequence, selection and iteration in Scratch, variables, events, broadcasts and debugging.
Instructions
- Time allowed
- 25 minutes
- Total marks
- 25
- Calculator
- No calculator is permitted.
- Answer all the questions.
- The number of marks for each question is shown in brackets. Use it as a guide to how much to write.
- The clock at the top counts down from the real time allowed. When it reaches zero the paper is locked and marked, as it would be collected in the exam hall.
- Read every question to the end before answering. Where a question says tick two boxes, tick exactly two: ticking more than asked scores nothing. Type one word and number answers carefully, because they are marked exactly.
Questions
Answer every question, then finish the paper to have it marked. Marking as you go teaches you far less.
Tick one box.
- LB A set of step by step instructions to solve a problem
An algorithm is a precise sequence of steps that solves a problem.
| Sequence | Selection | Iteration | |
|---|---|---|---|
| if touching edge then | |||
| repeat 10 | |||
| Blocks joined one after another and run in order | |||
| if score = 5 then ... else |
Tick one box in each row.
- Lif touching edge then: Selection
- Lrepeat 10: Iteration
- LBlocks joined one after another and run in order: Sequence
- Lif score = 5 then ... else: Selection
if blocks are selection, repeat and forever are iteration, and blocks in order are sequence.
when green flag clicked
set [score] to 0
repeat 5
change [score] by 2
end
say (score)- L10
The loop runs five times, adding 2 each time: 0 + 2 + 2 + 2 + 2 + 2 = 10.
repeat 4
change x by 25
end- L100
Four moves of 25 is 100.
Tick one box.
- LD when green flag clicked
when green flag clicked is the event that starts scripts when the green flag is pressed.
Tick one box.
- LC A named store for a value that can change while the program runs
A variable is a named store, such as score, whose value can change.
Tick one box.
- LA forever
forever keeps checking for as long as the game runs. repeat 10 would only check ten times.
pen down
repeat 3
move 100 steps
turn 120 degrees
end- Ltriangle
Three equal sides with a 120 degree turn at each corner make an equilateral triangle.
- L90
A square has four corners and the turns must add up to 360, so 360 / 4 = 90 degrees.
- LIt sends a message to other sprites or the stage
- LScripts that start with when I receive that message then run, so one sprite can make others act
A broadcast sends a message to every sprite and the stage. Any script that begins with when I receive that message starts running, so one sprite can make other sprites act, for example starting the next level.
Tick one box.
- LA Finding and fixing a mistake that makes a sprite move the wrong way
Debugging means finding and fixing errors in a program.
if <(score) > 10> then
say [Great]
else
say [Keep going]
end| score | The sprite says |
|---|---|
| 5 | |
| 10 | |
| 11 |
- LKeep going
- LKeep going
- LGreat
Only a score greater than 10 says Great. 10 is not greater than 10, so it says Keep going.
- LThe score is set back to 0 inside the loop, every time round
- LThe change score block is not run: the condition is never true, it is in the wrong place, or it changes by 0 or the wrong variable
The score might be set to 0 inside the forever loop, so it is reset every time round. Or the change score by 1 block never runs, because the if condition is never true, the block is not joined to the script, or it changes a different variable.
Tick two boxes.
- LC when this sprite clicked
- LD when space key pressed
- LNo marks if more than 2 boxes are ticked
Event blocks start scripts when something happens, such as a click or a key press.
Tick one box.
- LB Repeating a set of instructions
Iteration is repetition: a loop.
repeat 3
repeat 4
play sound [pop]
end
end- L12
The inner loop plays the sound 4 times, and it runs 3 times: 3 x 4 = 12.
Tick one box.
- LA Pauses the script for one second
It pauses that script for one second before the next block runs.
This is an original Key Stage 3 assessment. Most questions are closed, so the marking is exact, and the written answers are marked against a mark scheme in the same style as a GCSE paper, so the format is familiar long before it counts.