FOR loop with STEP (7a)

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Quick Questions

Shade in the A or B circle for each question.

1. Which FOR loop counts up in twos?

A FOR Count ← 2 TO 10 STEP 2

B FOR Count ← 2 TO 10 STEP 10

2. Which FOR loop counts down from 5 to 1?

A FOR Count ← 5 TO 1 STEP -1

B FOR Count ← 5 TO 1 STEP 1

3. What does STEP do in a FOR loop?

A It sets how many times the loop body is written in the code

B It sets how much the loop variable changes each time

4. What values does FOR X ← 1 TO 9 STEP 3 give?

A 1, 4, 7, 10

B 1, 4, 7

5. A loop starts at 10 and ends at 0. Which STEP is needed?

A STEP -2

B STEP 2

Match the Pairs

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

Left column		Right column
1FOR Count ← 2 TO 10 STEP 2		AFOR Number ← 10 TO 0 STEP -1
2FOR Count ← 5 TO 1 STEP -1		BThe step is negative, so the value goes down from 1 and never reaches 9. It should be STEP 2 to count up in twos.
3To count down from 10 to 0 in a FOR loop, the step must be negative		CCount goes 5, 4, 3, 2, 1 because the negative step makes it decrease by 1 each time
4To output only the even numbers from 2 to 20, the loop uses a step of 2		DFOR Number ← 2 TO 20 STEP 2
5FOR Count ← 10 TO 1 STEP 1		EThe loop is meant to count down, but STEP 1 makes the value go up, so it moves away from the end value. It should use STEP -1.
6FOR Count ← 1 TO 9 STEP -2		FCount goes 2, 4, 6, 8, 10 because the step makes it increase by 2 each time

Definitions

STEP

Fill in the Blanks

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

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

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

FOR Num ← 2 TO 10 STEP _ OUTPUT Num NEXT Num

FOR Count ← 5 TO 1 STEP -1 OUTPUT Count NEXT _____

FOR Count ← 20 __ 0 STEP -5 OUTPUT Count NEXT Count

Spot the Error

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

Question 1

A FOR Count ← 0 TO 10 STEPS 2

B OUTPUT Count

C NEXT Count

Question 2

A OUTPUT "Countdown"

B FOR Num ← 10 TO 1 STEP 1

C OUTPUT Num

D NEXT Num

Question 3

A Total ← 0

B FOR Num ← 2 TO 10 STEP 2

C Total ← Total + Num

D NEXT Total

Question 4

A DECLARE Num : INTEGER

B FOR Num ← 10 TO 0 STEP -2

C OUTPUT Number

D NEXT Num

Question 5

A Total ← 0

B FOR Count ← 1 TO 9 STEP 2

C Total ← Total + STEP

D NEXT Count

Answer Key

FOR loop with STEP (7a)

Section A: Quick Questions

A — FOR Count ← 2 TO 10 STEP 2

A — FOR Count ← 5 TO 1 STEP -1

B — It sets how much the loop variable changes each time

B — 1, 4, 7

A — STEP -2

Section B: Match the Pairs

FOR Count ← 2 TO 10 STEP 2 → Count goes 2, 4, 6, 8, 10 because the step makes it increase by 2 each time

FOR Count ← 5 TO 1 STEP -1 → Count goes 5, 4, 3, 2, 1 because the negative step makes it decrease by 1 each time

To count down from 10 to 0 in a FOR loop, the step must be negative → FOR Number ← 10 TO 0 STEP -1

To output only the even numbers from 2 to 20, the loop uses a step of 2 → FOR Number ← 2 TO 20 STEP 2

FOR Count ← 10 TO 1 STEP 1 → The loop is meant to count down, but STEP 1 makes the value go up, so it moves away from the end value. It should use STEP -1.

FOR Count ← 1 TO 9 STEP -2 → The step is negative, so the value goes down from 1 and never reaches 9. It should be STEP 2 to count up in twos.

Section C: Definitions

STEP — Used in a FOR loop to set how much the loop variable changes each time. STEP 2 counts in twos and STEP -1 counts down. The loop stops when the value goes past the end.

Section D: Fill in the Blanks

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

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

FOR Num ← 2 TO 10 STEP 2
  OUTPUT Num
NEXT Num

FOR Count ← 5 TO 1 STEP -1
  OUTPUT Count
NEXT Count

FOR Count ← 20 TO 0 STEP -5
  OUTPUT Count
NEXT Count

Section E: Spot the Error

A — The keyword is STEP, not STEPS. The line should be FOR Count ← 0 TO 10 STEP 2.

B — To count down from 10 to 1 the step must be negative. With STEP 1 the value starts past the end, so the loop never runs. It should be STEP -1.

D — NEXT must name the loop variable, which is Num, not Total. The line should be NEXT Num.

C — The loop variable is Num, so Number is a different identifier that was never declared. The line should be OUTPUT Num.

C — STEP is a keyword that sets the size of the change. It is not a value you can add. The loop variable Count holds the current value, so it should be Total ← Total + Count.