Nested IF statements (7a)

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Quick Questions

Shade in the A or B circle for each question.

1. Which describes a nested IF?

A Two separate IF statements written one after the other

B An IF statement written inside the THEN or ELSE part of another IF

2. When does the inner IF of a nested IF run?

A Only when the outer condition leads to it

B Every time the program runs

3. A program has one IF with another IF inside its THEN part. How many ENDIFs does it need?

A Two, one for each IF

B One, shared by both IFs

4. Which shows correct indentation for a nested IF?

A The inner IF starts at the same position as the outer IF

B The inner IF is indented a further two spaces inside the outer IF

5. Where should the inner ENDIF be written?

A Before the outer ENDIF, lined up with the inner IF

B After the outer ENDIF, lined up with the outer IF

Match the Pairs

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

Left column		Right column
1IF Mark >= 50 THEN IF Mark >= 80 THEN		AEach IF has its own ENDIF: the inner one closes first, then the outer one
2 ENDIF ENDIF		BThe second IF is nested inside the THEN part, so it is only checked when Mark is at least 50
3A nested IF can be put in the ELSE part, so it is only reached when the outer condition is false		CThe outer IF has no ENDIF, because only the inner IF was closed. Each IF needs its own ENDIF.
4Choosing between three outcomes needs a nested IF, with the code indented two more spaces		DThe nested IF is not indented by two more spaces, so it is hard to see that it sits inside the ELSE.
5IF Mark >= 50 THEN IF Mark >= 80 THEN OUTPUT "Merit" ENDIF		EIF Age >= 18 THEN OUTPUT "Adult" ELSE IF Age >= 13 THEN
6IF Mark >= 50 THEN OUTPUT "Pass" ELSE IF Mark >= 40 THEN OUTPUT "Near" ENDIF ENDIF		FIF Score >= 50 THEN OUTPUT "Pass" ELSE IF Score >= 40 THEN OUTPUT "Near" ELSE OUTPUT "Fail" ENDIF ENDIF

Definitions

nested IF

Fill in the Blanks

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

IF Score >= 50 THEN __ Score >= 80 THEN OUTPUT "Distinction"

IF Age >= 13 THEN IF Age <= 19 ____ OUTPUT "Teenager"

OUTPUT "Distinction" _____ ENDIF

IF Mark >= 50 THEN OUTPUT "Pass" ____

IF Temp > 0 THEN IF Temp _ 25 THEN OUTPUT "Mild"

Spot the Error

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

Question 1

A IF Mark >= 50 DO

B IF Mark >= 80 THEN

C OUTPUT "Distinction"

D ENDIF

E ENDIF

Question 2

A IF Age >= 13 THEN

B IF HasPermission ← TRUE THEN

C OUTPUT "Welcome"

D ENDIF

E ENDIF

Question 3

A IF Age >= 18 THEN

B IF HasLicence = TRUE THEN

C OUTPUT "Can drive"

D ENDWHILE

E ENDIF

Question 4

A INPUT Mark

B IF Mark >= 50 THEN

C IF Mark => 80 THEN

D OUTPUT "Merit"

E ENDIF

F ENDIF

Question 5

A OUTPUT Age

B IF Age >= 13 THEN

C IF Age <= 19 THEN

D OUTPUT "Teenager"

E ENDIF

F ENDIF

Answer Key

Nested IF statements (7a)

Section A: Quick Questions

B — An IF statement written inside the THEN or ELSE part of another IF

A — Only when the outer condition leads to it

A — Two, one for each IF

B — The inner IF is indented a further two spaces inside the outer IF

A — Before the outer ENDIF, lined up with the inner IF

Section B: Match the Pairs

IF Mark >= 50 THEN IF Mark >= 80 THEN → The second IF is nested inside the THEN part, so it is only checked when Mark is at least 50

ENDIF ENDIF → Each IF has its own ENDIF: the inner one closes first, then the outer one

A nested IF can be put in the ELSE part, so it is only reached when the outer condition is false → IF Age >= 18 THEN OUTPUT "Adult" ELSE IF Age >= 13 THEN

Choosing between three outcomes needs a nested IF, with the code indented two more spaces → IF Score >= 50 THEN OUTPUT "Pass" ELSE IF Score >= 40 THEN OUTPUT "Near" ELSE OUTPUT "Fail" ENDIF ENDIF

IF Mark >= 50 THEN IF Mark >= 80 THEN OUTPUT "Merit" ENDIF → The outer IF has no ENDIF, because only the inner IF was closed. Each IF needs its own ENDIF.

IF Mark >= 50 THEN OUTPUT "Pass" ELSE IF Mark >= 40 THEN OUTPUT "Near" ENDIF ENDIF → The nested IF is not indented by two more spaces, so it is hard to see that it sits inside the ELSE.

Section C: Definitions

nested IF — An IF statement written inside the THEN or ELSE part of another IF. It only runs when the outer condition leads to it, and each IF needs its own ENDIF.

Section D: Fill in the Blanks

IF Score >= 50 THEN
  IF Score >= 80 THEN
    OUTPUT "Distinction"

IF Age >= 13 THEN
  IF Age <= 19 THEN
    OUTPUT "Teenager"

    OUTPUT "Distinction"
  ENDIF
ENDIF

IF Mark >= 50 THEN
  OUTPUT "Pass"
ELSE

IF Temp > 0 THEN
  IF Temp < 25 THEN
    OUTPUT "Mild"

Section E: Spot the Error

A — An IF statement must use THEN after its condition, not DO. The outer IF should read IF Mark >= 50 THEN.

B — The ← symbol is for assignment. A condition compares values with =, so the nested IF should read IF HasPermission = TRUE THEN.

D — Every IF, including a nested one, must be closed with its own ENDIF. ENDWHILE belongs to a WHILE loop, so this line should be ENDIF.

C — The 'greater than or equal to' operator is >=, not =>. The nested IF should read IF Mark >= 80 THEN.

A — The program must read the age with INPUT so the IF statements have a value to test. OUTPUT would only display Age, so line 1 should be INPUT Age.