Choosing between several paths

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Quick Questions

Shade in the A or B circle for each question.

1. What does ELSE IF do in an algorithm?

A Checks another condition when the first one is false

B Repeats the steps again and again

2. An algorithm has IF, ELSE IF and ELSE. How many paths can it choose from?

A Only two paths

B Three paths

3. IF it is raining THEN take an umbrella. ELSE IF it is sunny THEN wear a hat. It is raining and sunny at once. What happens?

A Take an umbrella AND wear a hat, because both are true

B Take an umbrella, because the first true condition is the one that runs

4. In what order does the algorithm check the conditions?

A In order, from the top down

B All at the same time

5. What is the job of the final ELSE?

A A catch-all that runs when none of the conditions are true

B It checks one more condition before it runs

Match the Pairs

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

Left column		Right column
1ELSE IF temperature < 25 THEN		AA catch-all path that runs when none of the conditions above were true
2ELSE Wear a t-shirt		BIF temp > 30 THEN Stay inside ELSE IF temp > 20 THEN Go to the park ELSE Wear a jacket
3Conditions are checked in order from the top, and only the first true one runs		CThe ELSE is before the ELSE IF. The catch-all ELSE must be last, otherwise the ELSE IF can never be checked.
4Using ELSE IF lets an algorithm choose between three paths: hot, mild or cold		DIF score >= 90 THEN Show A ELSE IF score >= 70 THEN Show B
5IF mark >= 80 THEN Say Great ELSE IF Say Good job		EChecks a second condition only when the first condition was false
6IF age < 5 THEN Say Toddler ELSE Say Child ELSE IF age < 13 THEN Say Kid		FThe ELSE IF has no condition. It needs one, such as ELSE IF mark >= 50 THEN.

Definitions

ELSE IF

Fill in the Blanks

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

IF temp > 30 THEN DISPLAY "Hot" _______ temp > 20 THEN DISPLAY "Warm" ELSE DISPLAY "Cold"

IF mark >= 80 THEN grade ← "A" ELSE IF mark >= 50 THEN grade ← "B" ____ grade ← "C"

IF light = "red" THEN DISPLAY "Stop" ELSE IF light = "yellow" ____ DISPLAY "Slow" ELSE DISPLAY "Go"

IF coins >= 10 THEN DISPLAY "Big" ELSE IF coins __ 5 THEN DISPLAY "Medium" ELSE DISPLAY "Small"

IF weather = "rain" THEN DISPLAY "Coat" ELSE __ weather = "sun" THEN DISPLAY "Hat" ELSE DISPLAY "Jumper"

Spot the Error

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

Question 1

A SET score TO 95

B IF score >= 50 THEN

C SAY "Gold"

D ELSE IF score >= 50 THEN

E SAY "Silver"

F ELSE SAY "Bronze"

Question 2

A IF weather = "rainy"

B SAY "Take an umbrella"

C ELSE IF weather = "sunny" THEN

D SAY "Wear sunscreen"

E ELSE

F SAY "Wear a jacket"

Question 3

A IF light = "red" THEN

B SAY "Stop"

C ELSE light = "yellow" THEN

D SAY "Slow down"

E ELSE

F SAY "Go"

Question 4

A SET speed TO 45

B IF speed < 60 THEN

C SAY "Too fast"

D ELSE IF speed > 40 THEN

E SAY "Just right"

F ELSE SAY "Too slow"

Question 5

A IF pet = "dog" THEN

B SAY "Take it for a walk"

C IF pet = "fish" THEN

D SAY "Clean the tank"

E ELSE

F SAY "Give it a cuddle"

Answer Key

Choosing between several paths

Section A: Quick Questions

A — Checks another condition when the first one is false

B — Three paths

B — Take an umbrella, because the first true condition is the one that runs

A — In order, from the top down

A — A catch-all that runs when none of the conditions are true

Section B: Match the Pairs

ELSE IF temperature < 25 THEN → Checks a second condition only when the first condition was false

ELSE Wear a t-shirt → A catch-all path that runs when none of the conditions above were true

Conditions are checked in order from the top, and only the first true one runs → IF score >= 90 THEN Show A ELSE IF score >= 70 THEN Show B

Using ELSE IF lets an algorithm choose between three paths: hot, mild or cold → IF temp > 30 THEN Stay inside ELSE IF temp > 20 THEN Go to the park ELSE Wear a jacket

IF mark >= 80 THEN Say Great ELSE IF Say Good job → The ELSE IF has no condition. It needs one, such as ELSE IF mark >= 50 THEN.

IF age < 5 THEN Say Toddler ELSE Say Child ELSE IF age < 13 THEN Say Kid → The ELSE is before the ELSE IF. The catch-all ELSE must be last, otherwise the ELSE IF can never be checked.

Section C: Definitions

ELSE IF — Checks another condition when the first one is false, so an algorithm can pick from more than two paths. Conditions are checked in order and only one path runs.

Section D: Fill in the Blanks

IF temp > 30 THEN DISPLAY "Hot"
ELSE IF temp > 20 THEN DISPLAY "Warm"
ELSE DISPLAY "Cold"

IF mark >= 80 THEN grade ← "A"
ELSE IF mark >= 50 THEN grade ← "B"
ELSE grade ← "C"

IF light = "red" THEN DISPLAY "Stop"
ELSE IF light = "yellow" THEN DISPLAY "Slow"
ELSE DISPLAY "Go"

IF coins >= 10 THEN DISPLAY "Big"
ELSE IF coins >= 5 THEN DISPLAY "Medium"
ELSE DISPLAY "Small"

IF weather = "rain" THEN DISPLAY "Coat"
ELSE IF weather = "sun" THEN DISPLAY "Hat"
ELSE DISPLAY "Jumper"

Section E: Spot the Error

B — Conditions are checked in order. A score of 95 is at least 50, so it would get Silver and never reach the Gold check. The line should be IF score >= 90 THEN.

A — The IF line is missing the word THEN. It should be IF weather = "rainy" THEN.

C — To check another condition you need the words ELSE IF together. The line should be ELSE IF light = "yellow" THEN.

B — The comparison points the wrong way. Speed 45 is less than 60, so it would say Too fast. The line should be IF speed > 60 THEN.

C — This should be ELSE IF. A plain IF starts a new check, so a dog would get the walk and also the cuddle. With ELSE IF only one path runs.