A loop inside a loop

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Quick Questions

Shade in the A or B circle for each question.

1. An outer REPEAT 3 TIMES has an inner REPEAT 4 TIMES. How many times does the inner step run in total?

A 12 times

B 7 times

2. Which statement describes a nested loop correctly?

A A REPEAT placed inside another REPEAT

B Two REPEATs written one after the other

3. Each time the outer loop repeats once, what does the inner loop do?

A It runs only once

B It runs all of its repeats again

4. Which layout shows both loops indented correctly? A: REPEAT 2 TIMES, then the inner REPEAT indented, then its step indented twice B: REPEAT 2 TIMES, then the inner REPEAT, then its step, all at the left edge

A A

B B

5. How many END REPEAT lines does an algorithm with two nested loops need?

A One, shared by both loops

B Two, one for each REPEAT

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1REPEAT 3 TIMES REPEAT 4 TIMES SAY "Hi"		ANothing is indented, so it is hard to see that the inner loop sits inside the outer loop. Both loops should be indented.
2REPEAT 2 TIMES REPEAT 5 TIMES SAY "Go"		BREPEAT 4 TIMES REPEAT 3 TIMES CHECK SEAT END REPEAT END REPEAT
3Both loops are indented so you can see which loop sits inside the other, and each loop is closed with its own END REPEAT.		CREPEAT 3 TIMES REPEAT 2 TIMES SAY "Step" END REPEAT END REPEAT
4The inner loop is a complete REPEAT that starts over for each outer repeat, like 4 rows of 3 seats gives 12 seat checks.		DThere is only one END REPEAT for two loops. Each loop needs its own END REPEAT, so a second one is missing.
5REPEAT 3 TIMES REPEAT 4 TIMES SAY "Hi" END REPEAT		EThe inner loop runs 5 times for each of the 2 outer repeats, so Go is said 10 times.
6REPEAT 3 TIMES REPEAT 4 TIMES SAY "Hi" END REPEAT END REPEAT		FThe inner loop runs 4 times for each of the 3 outer repeats, so Hi is said 12 times.

Definitions

nested loop

Fill in the Blanks

Complete each line of code by filling in the missing parts.

REPEAT 3 TIMES ______ 4 TIMES PRINT "*"

SET outer ← 3 SET inner ← 4 SET passes ← outer _ inner

PRINT "*" __________ END REPEAT

REPEAT 2 TIMES REPEAT _ TIMES PRINT "ping" // 10 pings in all

REPEAT _ TIMES REPEAT 4 TIMES PRINT "x" // 12 inner passes in all

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A REPEAT 3

B REPEAT 4 TIMES

C OUTPUT "*"

D END REPEAT

E END REPEAT

Question 2

A REPEAT 3 TIMES

B REPEAT TIMES 4

C ADD 1 TO total

D END REPEAT

E END REPEAT

Question 3

A REPEAT 2 TIMES

B REPEAT UNTIL 5 TIMES

C OUTPUT "x"

D END REPEAT

E END REPEAT

Question 4

A REPEAT 3 TIMES

B REPEAT 4 TIMES

C OUTPUT "*"

D END IF

E END REPEAT

Question 5

A REPEAT 3 TIMES

B OUTPUT "Row"

C REPEAT 4 STEPS

D OUTPUT "*"

E END REPEAT

F END REPEAT

Answer Key

A loop inside a loop

Section A: Quick Questions

A — 12 times

A — A REPEAT placed inside another REPEAT

B — It runs all of its repeats again

A — A

B — Two, one for each REPEAT

Section B: Match the Pairs

REPEAT 3 TIMES REPEAT 4 TIMES SAY "Hi" → The inner loop runs 4 times for each of the 3 outer repeats, so Hi is said 12 times.

REPEAT 2 TIMES REPEAT 5 TIMES SAY "Go" → The inner loop runs 5 times for each of the 2 outer repeats, so Go is said 10 times.

Both loops are indented so you can see which loop sits inside the other, and each loop is closed with its own END REPEAT. → REPEAT 3 TIMES REPEAT 2 TIMES SAY "Step" END REPEAT END REPEAT

The inner loop is a complete REPEAT that starts over for each outer repeat, like 4 rows of 3 seats gives 12 seat checks. → REPEAT 4 TIMES REPEAT 3 TIMES CHECK SEAT END REPEAT END REPEAT

REPEAT 3 TIMES REPEAT 4 TIMES SAY "Hi" END REPEAT → There is only one END REPEAT for two loops. Each loop needs its own END REPEAT, so a second one is missing.

REPEAT 3 TIMES REPEAT 4 TIMES SAY "Hi" END REPEAT END REPEAT → Nothing is indented, so it is hard to see that the inner loop sits inside the outer loop. Both loops should be indented.

Section C: Definitions

nested loop — A REPEAT placed inside another REPEAT. The inner loop runs all its repeats again for every repeat of the outer loop, so an outer 3 and an inner 4 gives 12 inner passes.

Section D: Fill in the Blanks

REPEAT 3 TIMES
  REPEAT 4 TIMES
    PRINT "*"

SET outer ← 3
SET inner ← 4
SET passes ← outer * inner

    PRINT "*"
  END REPEAT
END REPEAT

REPEAT 2 TIMES
  REPEAT 5 TIMES
    PRINT "ping"  // 10 pings in all

REPEAT 3 TIMES
  REPEAT 4 TIMES
    PRINT "x"  // 12 inner passes in all

Section E: Spot the Error

A — The outer loop must say how many repeats it makes using the word TIMES. It should be 'REPEAT 3 TIMES'.

B — The inner loop has the words in the wrong order. A counted loop is written REPEAT then the number then TIMES, so it should be ' REPEAT 4 TIMES'.

B — This mixes two kinds of loop. A set-count loop is written REPEAT 5 TIMES. REPEAT UNTIL needs a condition, not a number of times.

D — The inner loop is closed with END REPEAT, not END IF. Line 4 should be ' END REPEAT'.

C — A counted loop uses the keyword TIMES, not STEPS. The inner loop should be ' REPEAT 4 TIMES'.