Totalling in a loop (8.1b)

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Quick Questions

Shade in the A or B circle for each question.

1. Where should Total <- 0 be written when totalling values in a loop?

A Inside the loop, as the first line

B Before the loop starts

2. Which line adds the new value Number to the running total?

A Total <- Total + Number

B Number <- Total + Number

3. A student forgets to set Total <- 0 before the loop. What is the problem?

A Total has no starting value, so the answer may be wrong

B The loop will run one time too many

4. Which FOR loop correctly totals 5 numbers typed in by the user?

A Total <- 0 / FOR Count <- 1 TO 5 / INPUT Number / Total <- Total + Number / NEXT Count

B FOR Count <- 1 TO 5 / INPUT Number / Total <- 0 / Total <- Total + Number / NEXT Count

5. Where should OUTPUT Total be placed to show the final total of all the values?

A Inside the loop, before the total is added

B After the loop (after NEXT or ENDWHILE)

Match the Pairs

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

Left column		Right column
1Total <- 0		ATotal <- 0 INPUT Number WHILE Number <> -1 DO Total <- Total + Number INPUT Number ENDWHILE OUTPUT Total
2Total <- Total + Number		BTotal <- 0 is inside the loop, so the total is reset to zero on every repeat and only the last number is kept. It should be placed before the loop.
3Totalling ten values typed in by the user: set the total to 0, then add each input inside a FOR loop		CAdds the new value to the running total and stores the result back in Total each time round the loop
4Totalling until a rogue value is entered, then showing the total after the loop has finished		DTotal <- Number replaces the total with the latest value instead of adding to it. It should be Total <- Total + Number.
5FOR Count <- 1 TO 5 Total <- 0 INPUT Number Total <- Total + Number NEXT Count		ETotal <- 0 FOR Count <- 1 TO 10 INPUT Number Total <- Total + Number NEXT Count
6Total <- 0 FOR Count <- 1 TO 5 INPUT Number Total <- Number NEXT Count		FSets the running total to zero before the loop starts, so the adding begins from a known value

Definitions

Total <- Total + Number

Fill in the Blanks

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

Total <- _ FOR Count <- 1 TO 5 INPUT Number

FOR Count <- 1 TO 5 Total <- Total + ______ NEXT Count

INPUT Number Total <- _____ + Number NEXT Count

_____ Number <> -1 DO Total <- Total + Number INPUT Number

NEXT Count OUTPUT "Sum: ", _____

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 INPUT Number

D Total <- Number

E NEXT Count

F OUTPUT Total

Question 2

A Total <- 0

B FOR Count <- 1 UNTIL 3

C INPUT Number

D Total <- Total + Number

E NEXT Count

F OUTPUT Total

Question 3

A DECLARE Total : INTEGER

B Total <- 1

C FOR Count <- 1 TO 5

D INPUT Number

E Total <- Total + Number

F NEXT Count

Question 4

A Total <- 0

B INPUT Number

C WHILE Number <> -1 DO

D Total + Number <- Total

E INPUT Number

F ENDWHILE

Question 5

A Total <- 0

B WHILE

C INPUT Number

D Total <- Total + Number

E UNTIL Total >= 100

F OUTPUT Total

Answer Key

Totalling in a loop (8.1b)

Section A: Quick Questions

B — Before the loop starts

A — Total <- Total + Number

A — Total has no starting value, so the answer may be wrong

A — Total <- 0 / FOR Count <- 1 TO 5 / INPUT Number / Total <- Total + Number / NEXT Count

B — After the loop (after NEXT or ENDWHILE)

Section B: Match the Pairs

Total <- 0 → Sets the running total to zero before the loop starts, so the adding begins from a known value

Total <- Total + Number → Adds the new value to the running total and stores the result back in Total each time round the loop

Totalling ten values typed in by the user: set the total to 0, then add each input inside a FOR loop → Total <- 0 FOR Count <- 1 TO 10 INPUT Number Total <- Total + Number NEXT Count

Totalling until a rogue value is entered, then showing the total after the loop has finished → Total <- 0 INPUT Number WHILE Number <> -1 DO Total <- Total + Number INPUT Number ENDWHILE OUTPUT Total

FOR Count <- 1 TO 5 Total <- 0 INPUT Number Total <- Total + Number NEXT Count → Total <- 0 is inside the loop, so the total is reset to zero on every repeat and only the last number is kept. It should be placed before the loop.

Total <- 0 FOR Count <- 1 TO 5 INPUT Number Total <- Number NEXT Count → Total <- Number replaces the total with the latest value instead of adding to it. It should be Total <- Total + Number.

Section C: Definitions

Total <- Total + Number — Adds each new value to the running total inside a loop. Set Total <- 0 before the loop starts, then OUTPUT Total after the loop ends.

Section D: Fill in the Blanks

Total <- 0
FOR Count <- 1 TO 5
   INPUT Number

FOR Count <- 1 TO 5
   Total <- Total + Number
NEXT Count

   INPUT Number
   Total <- Total + Number
NEXT Count

WHILE Number <> -1 DO
   Total <- Total + Number
   INPUT Number

NEXT Count
OUTPUT "Sum: ", Total

Section E: Spot the Error

D — Total <- Number replaces the total with the latest value, so earlier values are lost. It should be Total <- Total + Number to add each value to the running total.

B — A FOR loop uses the keyword TO for its end value, not UNTIL. It should be FOR Count <- 1 TO 3.

B — The total must start at 0 before the loop. Starting at 1 makes every final total one too big. It should be Total <- 0.

D — The assignment is the wrong way round. The variable being updated goes on the left of <-. It should be Total <- Total + Number.

B — A loop that ends with UNTIL must begin with REPEAT, not WHILE. Line 2 should be REPEAT.