SUBSTRING function

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Quick Questions

Shade in the A or B circle for each question.

1. What does SUBSTRING("Happy Days", 1, 5) return?

A "Happy"

B "Happy "

2. In Cambridge pseudocode, which position is the first character of a string?

A Position 1

B Position 0

3. In SUBSTRING("Computer", 4, 3), what does the 3 mean?

A The position to stop at

B The number of characters to return

4. What does SUBSTRING("Computer", 4, 3) return?

A "put"

B "mpu"

5. Which line picks out only the first character of Code?

A SUBSTRING(Code, 1, 0)

B SUBSTRING(Code, 1, 1)

Match the Pairs

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

Left column		Right column
1SUBSTRING("Happy Days", 1, 5)		AIF SUBSTRING(ID, 1, 1) = "A" THEN
2SUBSTRING(Word, 3, 1)		BReturns just the third character of the string stored in Word
3Take the first 3 characters of a string called Code and store them in Prefix		CPrefix ← SUBSTRING(Code, 1, 3)
4A format check that tests whether the first character of ID is the letter A		DReturns "Happy": 5 characters starting at position 1, the first character
5SUBSTRING("Happy Days", 0, 5)		EThe length is the number of characters to take, not an end position. Starting at 7 with length 10 runs past the end of the string
6SUBSTRING("Happy Days", 7, 10)		FPosition 0 does not exist because the first character is at position 1, so the start value must be 1

Definitions

SUBSTRING("Happy Days", 1, 5)

Fill in the Blanks

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

_________("Happy Days", 1, 5)

SUBSTRING("Happy Days", _, 5)

Word ← SUBSTRING("Happy Days", 7, _)

Initial ← SUBSTRING(Name, 1, _) OUTPUT Initial

IF SUBSTRING(ID, 4, 1) __ "-" THEN OUTPUT "Invalid format" ENDIF

Spot the Error

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

Question 1

A Word ← "Happy Days"

B First ← SUBSTRING(Word, 0, 5)

C OUTPUT First

Question 2

A Letter ← SUBSTRING("Cloud", 3)

B OUTPUT Letter

C // Outputs o

Question 3

A DECLARE Code : STRING

B Code ← SUBSTRING(3, 3, "AB123")

C OUTPUT Code

Question 4

A INPUT Name

B Initial ← SUBSTRING(Name, 1, 1)

C OUTPUT "Initial"

Question 5

A Word ← "Computer"

B Total ← LENGTH(Word)

C FOR I ← 1 TO Total

D Ch ← SUBSTRING(Word, 1, I)

E OUTPUT Ch

F NEXT I

Answer Key

SUBSTRING function

Section A: Quick Questions

A — "Happy"

A — Position 1

B — The number of characters to return

A — "put"

B — SUBSTRING(Code, 1, 1)

Section B: Match the Pairs

SUBSTRING("Happy Days", 1, 5) → Returns "Happy": 5 characters starting at position 1, the first character

SUBSTRING(Word, 3, 1) → Returns just the third character of the string stored in Word

Take the first 3 characters of a string called Code and store them in Prefix → Prefix ← SUBSTRING(Code, 1, 3)

A format check that tests whether the first character of ID is the letter A → IF SUBSTRING(ID, 1, 1) = "A" THEN

SUBSTRING("Happy Days", 0, 5) → Position 0 does not exist because the first character is at position 1, so the start value must be 1

SUBSTRING("Happy Days", 7, 10) → The length is the number of characters to take, not an end position. Starting at 7 with length 10 runs past the end of the string

Section C: Definitions

SUBSTRING("Happy Days", 1, 5) — SUBSTRING(string, start, length) returns length characters beginning at position start. Position 1 is the first character, so this returns "Happy".

Section D: Fill in the Blanks

SUBSTRING("Happy Days", 1, 5)

Word ← SUBSTRING("Happy Days", 7, 4)

Initial ← SUBSTRING(Name, 1, 1)
OUTPUT Initial

IF SUBSTRING(ID, 4, 1) <> "-" THEN
  OUTPUT "Invalid format"
ENDIF

Section E: Spot the Error

B — In SUBSTRING the first character is at position 1, so a start of 0 is invalid. The line should be First ← SUBSTRING(Word, 1, 5), which gives "Happy".

A — SUBSTRING needs three arguments: the string, the start and the length. The length is missing. It should be SUBSTRING("Cloud", 3, 1) to pick out the single character "o".

B — The arguments are in the wrong order. SUBSTRING takes the string first, then the start position, then the length: SUBSTRING("AB123", 3, 3), which returns "123".

C — Putting Initial in quotes outputs the word Initial instead of the value stored in the variable. It should be OUTPUT Initial, with no quotes.

D — The start and length are swapped. To pick out one character at a time, the start must be I and the length must be 1: SUBSTRING(Word, I, 1).