Counters and accumulators in pseudocode

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. Which line sets up a counter correctly BEFORE a loop starts?

A count <- 0

B count <- count + 1

2. Which line adds 1 to a counter each time the loop repeats?

A count <- count + 1

B count <- 1

3. An accumulator keeps a running total of marks. Which line does this inside the loop?

A total <- mark

B total <- total + mark

4. True or false: you should set total <- 0 inside the loop so it starts fresh on every repeat.

A False: set total <- 0 before the loop

B True: set total <- 0 inside the loop

5. You want to count how many scores are above 50. Which code does this?

A count <- count + 1 then if score > 50

B if score > 50 then count <- count + 1

Match the Pairs

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

Left column		Right column
1count <- count + 1		AAn accumulator: adds the value of score to a running total each time the loop repeats
2total <- total + score		BThe accumulator adds 1 instead of the value being collected, so it only counts repeats. It should be total <- total + x.
3Set the counter to 0 before the loop so it starts from nothing		Cfor i from 1 to 5 if mark >= 50 then passes <- passes + 1 end if end for
4Count only the matches: add 1 only when a condition is true		Dcount <- 0 for i from 1 to 10 count <- count + 1 end for
5for i from 1 to 10 count <- 0 count <- count + 1 end for		EA counter: adds 1 to count each time the loop repeats
6total <- 0 for i from 1 to 5 total <- total + 1 end for		Fcount is set to 0 inside the loop, so it resets every repeat and always ends at 1. Move count <- 0 to before the loop.

Definitions

count <- count + 1

Fill in the Blanks

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

count <- _ for i from 1 to 10 count <- count + 1

total <- 0 for i from 1 to 5 total <- total + _

for i from 1 to 5 input score __ score > 50 then count <- count + 1

total <- 0 for i from 1 to 4 total <- total _ i

count <- 0 while count < 5 count <- _____ + 1

Spot the Error

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

Question 1

A input n

B total <- n

C for i from 1 to n

D total <- total + i

E print total

Question 2

A count <- 0

B for i from 1 to 8

C input age

D count <- 1

E print count

Question 3

A total <- 0

B for i from 1 to 5

C input price

D total <- total + 1

E print total

Question 4

A n <- 10

B counter <- 0

C for i from 1 to n

D count <- count + 1

E print count

Question 5

A count <- 3

B for i from 1 to 6

C input mark

D if mark >= 50 then

E count <- count + 1

F print count

Answer Key

Counters and accumulators in pseudocode

Section A: Quick Questions

A — count <- 0

A — count <- count + 1

B — total <- total + mark

A — False: set total <- 0 before the loop

B — if score > 50 then count <- count + 1

Section B: Match the Pairs

count <- count + 1 → A counter: adds 1 to count each time the loop repeats

total <- total + score → An accumulator: adds the value of score to a running total each time the loop repeats

Set the counter to 0 before the loop so it starts from nothing → count <- 0 for i from 1 to 10 count <- count + 1 end for

Count only the matches: add 1 only when a condition is true → for i from 1 to 5 if mark >= 50 then passes <- passes + 1 end if end for

for i from 1 to 10 count <- 0 count <- count + 1 end for → count is set to 0 inside the loop, so it resets every repeat and always ends at 1. Move count <- 0 to before the loop.

total <- 0 for i from 1 to 5 total <- total + 1 end for → The accumulator adds 1 instead of the value being collected, so it only counts repeats. It should be total <- total + x.

Section C: Definitions

count <- count + 1 — A counter. It adds 1 to a variable each time a loop repeats. Set it to 0 before the loop. An accumulator works the same way: total <- total + x adds a value each time.

Section D: Fill in the Blanks

count <- 0
for i from 1 to 10
    count <- count + 1

total <- 0
for i from 1 to 5
    total <- total + i

for i from 1 to 5
    input score
    if score > 50 then count <- count + 1

total <- 0
for i from 1 to 4
    total <- total + i

count <- 0
while count < 5
    count <- count + 1

Section E: Spot the Error

B — The running total must be set to 0 before the loop. Starting it at n adds an extra n to the answer. It should be total <- 0.

D — This line replaces count with 1 each time instead of adding 1, so count never gets above 1. It should be count <- count + 1.

D — An accumulator adds the value from each repeat, not just 1. Adding 1 only counts the prices. It should be total <- total + price.

B — The variable set to 0 is called counter, but the loop and print use count. The names must match. It should be count <- 0.

A — A counter must start at 0 before the loop. Starting at 3 makes the final count 3 too high. It should be count <- 0.