Creating my own algorithm with branching, repetition and a counter

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Quick Questions

Shade in the A or B circle for each question.

1. Which algorithm uses a decision, a loop and a counter together to count how many pencils in a tray are sharp?

A SET count TO 0. REPEAT for each pencil: IF it is sharp THEN ADD 1 to count. SAY count.

B SET count TO 0. REPEAT for each pencil: SAY pencil. SAY count.

2. A game algorithm gives the player 3 lives. Which part is the counter?

A SET lives TO 3, then SUBTRACT 1 each time the player is hit

B IF the player is hit THEN play a sound

3. Which recipe algorithm repeats a step the right number of times?

A SET eggs TO 0. REPEAT UNTIL eggs = 3: ADD 1 egg to the bowl, ADD 1 to eggs.

B SET eggs TO 0. ADD 1 egg to the bowl. ADD 1 to eggs. STOP.

4. Your classroom algorithm should count students who brought a hat. Where does the IF go?

A After the REPEAT, so it checks only the last student

B Inside the REPEAT, so it checks every student

5. You wrote an algorithm to count red cards. What is the best way to check that it works?

A Read the title and decide it looks right

B Follow it step by step with a small set of cards and track the count

Match the Pairs

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

Left column		Right column
1SET count TO 0 REPEAT 5 TIMES IF page is torn THEN ADD 1 TO count		AA school routine that checks 5 library books and counts how many pages are torn
2SET lives TO 3 REPEAT UNTIL lives = 0 IF hit THEN TAKE 1 FROM lives		BA game that keeps going until the player has lost all 3 lives
3A recipe algorithm that adds eggs one at a time, counts them and stops at 3		Ccount = 0, round 1: IF true THEN count = 1, round 2: IF false THEN count stays 1
4Checking your algorithm by following it step by step with a small starting value		DThe counter was never set to 0 before the loop, so we do not know what number it starts from.
5REPEAT 10 TIMES IF homework done THEN ADD 1 TO count		EIf the answer is wrong, score never changes, so the loop could never stop. The counter must go up each round, or the loop needs a way to end.
6SET score TO 0 REPEAT UNTIL score = 10 IF answer correct THEN ADD 1 TO score		FSET eggs TO 0 REPEAT UNTIL eggs = 3 ADD 1 egg ADD 1 TO eggs

Definitions

REPEAT + IF + count

Fill in the Blanks

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

SET count ← _ REPEAT 5 TIMES IF bag has book THEN ADD 1 to count

SET lives ← 3 REPEAT _____ lives = 0 IF hit THEN SET lives ← lives - 1

SET eggs ← 0 REPEAT 3 TIMES __ egg is fresh THEN ADD 1 to eggs

SET stirs ← 0 REPEAT UNTIL stirs = 10 SET stirs ← stirs _ 1

SET count ← 0 REPEAT 3 TIMES ADD 1 TO count SAY _____

Spot the Error

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

Question 1

A SET ready TO 0

B REPEAT 5 TIMES

C IF bag is packed

D ADD 1 TO ready

E END IF

F END REPEAT

Question 2

A SET stars TO 0

B REPEAT 3

C IF card is a star THEN

D ADD 1 TO stars

E END IF

F END REPEAT

Question 3

A SET stirs TO 0

B REPEAT UNTIL stirs = 10

C STIR the mixture

D SET stirs TO 1

E END REPEAT

Question 4

A SET cracked TO 6

B REPEAT 6 TIMES

C IF egg is cracked THEN

D ADD 1 TO cracked

E END IF

F END REPEAT

Question 5

A SET late TO 0

B REPEAT 5 TIMES

C IF student is late THEN

D ADD 1 TO days

E END IF

F END REPEAT

Answer Key

Creating my own algorithm with branching, repetition and a counter

Section A: Quick Questions

A — SET count TO 0. REPEAT for each pencil: IF it is sharp THEN ADD 1 to count. SAY count.

A — SET lives TO 3, then SUBTRACT 1 each time the player is hit

A — SET eggs TO 0. REPEAT UNTIL eggs = 3: ADD 1 egg to the bowl, ADD 1 to eggs.

B — Inside the REPEAT, so it checks every student

B — Follow it step by step with a small set of cards and track the count

Section B: Match the Pairs

SET count TO 0 REPEAT 5 TIMES IF page is torn THEN ADD 1 TO count → A school routine that checks 5 library books and counts how many pages are torn

SET lives TO 3 REPEAT UNTIL lives = 0 IF hit THEN TAKE 1 FROM lives → A game that keeps going until the player has lost all 3 lives

A recipe algorithm that adds eggs one at a time, counts them and stops at 3 → SET eggs TO 0 REPEAT UNTIL eggs = 3 ADD 1 egg ADD 1 TO eggs

Checking your algorithm by following it step by step with a small starting value → count = 0, round 1: IF true THEN count = 1, round 2: IF false THEN count stays 1

REPEAT 10 TIMES IF homework done THEN ADD 1 TO count → The counter was never set to 0 before the loop, so we do not know what number it starts from.

SET score TO 0 REPEAT UNTIL score = 10 IF answer correct THEN ADD 1 TO score → If the answer is wrong, score never changes, so the loop could never stop. The counter must go up each round, or the loop needs a way to end.

Section C: Definitions

REPEAT + IF + count — A finished algorithm joins steps, a decision (IF), a loop (REPEAT) and a counter to solve a school, game or recipe problem. You check it by following it step by step.

Section D: Fill in the Blanks

SET count ← 0
REPEAT 5 TIMES
  IF bag has book THEN ADD 1 to count

SET lives ← 3
REPEAT UNTIL lives = 0
  IF hit THEN SET lives ← lives - 1

SET eggs ← 0
REPEAT 3 TIMES
  IF egg is fresh THEN ADD 1 to eggs

SET stirs ← 0
REPEAT UNTIL stirs = 10
  SET stirs ← stirs + 1

SET count ← 0
REPEAT 3 TIMES ADD 1 TO count
SAY count

Section E: Spot the Error

C — An IF decision needs the word THEN after its condition. Line 3 should be: IF bag is packed THEN.

B — A set-number loop must say TIMES so we know it repeats a fixed number of times. Line 2 should be: REPEAT 3 TIMES.

D — Setting stirs to 1 each time means the counter never goes up past 1, so the loop never stops. Line 4 should be: ADD 1 TO stirs.

A — A counter must start at 0 before we begin counting. Starting at 6 gives the wrong total. Line 1 should be: SET cracked TO 0.

D — The counter being used is late, so we must add 1 to late. Adding to a different variable leaves late unchanged. Line 4 should be: ADD 1 TO late.