FOR ... TO ... NEXT

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Quick Questions

Shade in the A or B circle for each question.

1. Which FOR loop runs its statements exactly 30 times?

A FOR Index ← 1 TO 30

B FOR Index ← 1 TO 29

2. Which line correctly ends a loop that starts with FOR Count ← 1 TO 10?

A NEXT Count

B ENDFOR Count

3. The loop variable Index in FOR Index ← 1 TO 30 changes ...

A only when you write Index ← Index + 1 inside the loop

B automatically each time round the loop

4. What data type should the loop variable in a FOR loop be?

A INTEGER

B STRING

5. Which pair of lines is written correctly?

A FOR Index ← 1 TO 5 ... NEXT Count

B FOR Index ← 1 TO 5 ... NEXT Index

Match the Pairs

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

Left column		Right column
1FOR Index ← 1 TO 30		ANEXT uses a different identifier from the FOR line. It must repeat the same loop variable, so it should be NEXT Index.
2NEXT Index		BStarts a loop that repeats the statements below once for each whole number from 1 to 30 inclusive
3The loop variable changes by itself, so you never write a line to add 1 to it		CThe loop variable is given its start value with = instead of the assignment arrow. It should be FOR Index ← 1 TO 30.
4The loop variable is an INTEGER, so it must be declared as one before the loop		DFOR Count ← 1 TO 5 OUTPUT Count NEXT Count
5FOR Index ← 1 TO 30 OUTPUT Index NEXT Count		EDECLARE Index : INTEGER FOR Index ← 1 TO 30 OUTPUT Index NEXT Index
6FOR Index = 1 TO 30 OUTPUT Index NEXT Index		FEnds the FOR loop and names the same loop variable that the FOR line used

Definitions

FOR Index ← 1 TO 30

Fill in the Blanks

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

___ Index ← 1 TO 30 OUTPUT Index NEXT Index

FOR Index ← 1 __ 30 OUTPUT Index NEXT Index

FOR Number ← 1 TO 10 OUTPUT Number * 2 ____ Number

FOR Count ← 1 TO 5 OUTPUT Count NEXT _____

FOR Index _ 1 TO 30 OUTPUT Index NEXT Index

Spot the Error

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

Question 1

A Total ← 0

B FOR Index = 1 TO 30

C Total ← Total + Index

D NEXT Index

Question 2

A FOR Count ← 1 TO 5

B OUTPUT "Hello"

C OUTPUT Count

D NEXT Counter

Question 3

A Sum ← 0

B FOR Num ← 1 UNTIL 20

C Sum ← Sum + Num

D NEXT Num

Question 4

A DECLARE Index : INTEGER

B FOR Index ← 1.5 TO 30

C OUTPUT Index

D NEXT Index

Question 5

A Total ← 0

B FOR Index ← 1 TO 10

C Total ← Total + Number

D NEXT Index

E OUTPUT Total

Answer Key

FOR ... TO ... NEXT

Section A: Quick Questions

A — FOR Index ← 1 TO 30

A — NEXT Count

B — automatically each time round the loop

A — INTEGER

B — FOR Index ← 1 TO 5 ... NEXT Index

Section B: Match the Pairs

FOR Index ← 1 TO 30 → Starts a loop that repeats the statements below once for each whole number from 1 to 30 inclusive

NEXT Index → Ends the FOR loop and names the same loop variable that the FOR line used

The loop variable changes by itself, so you never write a line to add 1 to it → FOR Count ← 1 TO 5 OUTPUT Count NEXT Count

The loop variable is an INTEGER, so it must be declared as one before the loop → DECLARE Index : INTEGER FOR Index ← 1 TO 30 OUTPUT Index NEXT Index

FOR Index ← 1 TO 30 OUTPUT Index NEXT Count → NEXT uses a different identifier from the FOR line. It must repeat the same loop variable, so it should be NEXT Index.

FOR Index = 1 TO 30 OUTPUT Index NEXT Index → The loop variable is given its start value with = instead of the assignment arrow. It should be FOR Index ← 1 TO 30.

Section C: Definitions

FOR Index ← 1 TO 30 — Repeats the statements below once for each whole number from 1 to 30 inclusive. Index is an INTEGER that changes automatically each time. Close the loop with NEXT Index.

Section D: Fill in the Blanks

FOR Index ← 1 TO 30
    OUTPUT Index
NEXT Index

FOR Index ← 1 TO 30
    OUTPUT Index
NEXT Index

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

FOR Count ← 1 TO 5
    OUTPUT Count
NEXT Count

FOR Index ← 1 TO 30
    OUTPUT Index
NEXT Index

Section E: Spot the Error

B — A FOR loop gives its loop variable a starting value with the assignment arrow ←, not =. It should be FOR Index ← 1 TO 30.

D — NEXT must repeat the same identifier that follows FOR. The loop variable is Count, so the line should be NEXT Count.

B — The end value of a FOR loop is introduced with TO, not UNTIL. UNTIL belongs to REPEAT loops. It should be FOR Num ← 1 TO 20.

B — The loop variable is an INTEGER, so it must start at a whole number. 1.5 is a REAL. It should be FOR Index ← 1 TO 30.

C — Number has never been set. The loop variable is Index, which changes automatically each time round, so the line should be Total ← Total + Index.