FOR…TO…NEXT loop (7d)

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Quick Questions

Shade in the A or B circle for each question.

1. How many times does this loop run? FOR Count ← 1 TO 5 OUTPUT Count NEXT Count

A 5 times

B 4 times

2. Which line correctly ends a loop that begins FOR Index ← 1 TO 8?

A NEXT Index

B ENDFOR Index

3. Inside FOR Count ← 1 TO 10, what do you need to write to add 1 to Count each time round?

A Count ← Count + 1 on the last line

B Nothing, the loop does it automatically

4. What is the first value of Count in FOR Count ← 3 TO 7?

A 3

B 4

5. What does STEP 2 do in FOR Count ← 1 TO 9 STEP 2?

A The loop runs exactly 2 times

B Count goes up by 2 each time: 1, 3, 5, 7, 9

Match the Pairs

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

Left column		Right column
1FOR Count ← 1 TO 5		AFOR Count ← 2 TO 10 STEP 2
2NEXT Count		BNEXT does not name the loop variable. It should be NEXT Count.
3A FOR loop with STEP 2 jumps by 2 each time, so Count takes the values 2, 4, 6, 8, 10		CStarts a loop where Count is 1, 2, 3, 4, 5, so the lines inside repeat 5 times
4A complete FOR loop that outputs the numbers 1 to 3 using the loop variable		DFOR Count ← 1 TO 3 OUTPUT Count NEXT Count
5FOR Count ← 1 TO 5 OUTPUT Count NEXT		EMarks the end of the FOR loop and names the loop variable that is increased by 1
6FOR Count ← 1 TO 5 OUTPUT Count Count ← Count + 1 NEXT Count		FCount is increased inside the loop by hand. A FOR loop changes the loop variable automatically, so this line is wrong and should be removed.

Definitions

FOR Count ← 1 TO 10

Fill in the Blanks

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

FOR Count ← 1 __ 5 OUTPUT Count NEXT Count

___ Count ← 1 TO 10 OUTPUT Count * 2 NEXT Count

FOR Total ← 1 TO 8 OUTPUT Total NEXT _____

FOR Count ← 0 TO 10 ____ 2 OUTPUT Count NEXT Count

FOR Count ← 10 TO 1 STEP __ OUTPUT Count NEXT Count

Spot the Error

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

Question 1

A Total ← 0

B FOR Count = 1 TO 5

C Total ← Total + Count

D NEXT Count

E OUTPUT Total

Question 2

A FOR Count ← 1 TO 5

B OUTPUT Count

C NEXT Counter

D OUTPUT "Done"

Question 3

A FOR Num ← 1 TO 4

B OUTPUT Num * 2

C ENDFOR

Question 4

A Total ← 0

B FOR Count ← 1 TO 4

C OUTPUT Count

D Count ← Count + 1

E NEXT Count

F OUTPUT Total

Question 5

A Total ← 0

B FOR Count ← 1 TO 10 STEP 2

C Total ← Total + Count

D NEXT

E OUTPUT Total

Answer Key

FOR…TO…NEXT loop (7d)

Section A: Quick Questions

A — 5 times

A — NEXT Index

B — Nothing, the loop does it automatically

A — 3

B — Count goes up by 2 each time: 1, 3, 5, 7, 9

Section B: Match the Pairs

FOR Count ← 1 TO 5 → Starts a loop where Count is 1, 2, 3, 4, 5, so the lines inside repeat 5 times

NEXT Count → Marks the end of the FOR loop and names the loop variable that is increased by 1

A FOR loop with STEP 2 jumps by 2 each time, so Count takes the values 2, 4, 6, 8, 10 → FOR Count ← 2 TO 10 STEP 2

A complete FOR loop that outputs the numbers 1 to 3 using the loop variable → FOR Count ← 1 TO 3 OUTPUT Count NEXT Count

FOR Count ← 1 TO 5 OUTPUT Count NEXT → NEXT does not name the loop variable. It should be NEXT Count.

FOR Count ← 1 TO 5 OUTPUT Count Count ← Count + 1 NEXT Count → Count is increased inside the loop by hand. A FOR loop changes the loop variable automatically, so this line is wrong and should be removed.

Section C: Definitions

FOR Count ← 1 TO 10 — Repeats the lines up to NEXT Count a fixed number of times. Count starts at 1, goes up automatically, and both the start and end values are included. STEP changes the jump.

Section D: Fill in the Blanks

FOR Count ← 1 TO 5
  OUTPUT Count
NEXT Count

FOR Count ← 1 TO 10
  OUTPUT Count * 2
NEXT Count

FOR Total ← 1 TO 8
  OUTPUT Total
NEXT Total

FOR Count ← 0 TO 10 STEP 2
  OUTPUT Count
NEXT Count

FOR Count ← 10 TO 1 STEP -1
  OUTPUT Count
NEXT Count

Section E: Spot the Error

B — The start value of a FOR loop is given with the assignment arrow, not an equals sign. It should be FOR Count ← 1 TO 5.

C — NEXT must name the same loop variable that the FOR line uses. The loop variable is Count, so it should be NEXT Count.

C — Cambridge pseudocode ends a FOR loop with NEXT followed by the loop variable, not ENDFOR. It should be NEXT Num.

D — The loop variable goes up automatically, so it must not be changed by hand inside the loop. This line also means Total is never added to. It should be Total ← Total + Count.

D — NEXT must be followed by the name of the loop variable. It should be NEXT Count.