SUBSTRING: extracting part of a string

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

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

A "Happy"

B "Days"

2. In SUBSTRING("Computer", 1, 3), what does the last number (3) mean?

A How many characters to take

B The position where the extract stops

3. Which call returns "i" from the string "Science"?

A SUBSTRING("Science", 1, 3)

B SUBSTRING("Science", 3, 1)

4. What does SUBSTRING("Pizza", 2, 1) return?

A "iz"

B "i"

5. What is the data type of the result of SUBSTRING("Pizza", 2, 1)?

A STRING, even though it is one character

B CHAR, because it is one character

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)		AReturns "Happy": 5 characters taken from position 1
2SUBSTRING(Word, 3, 1)		BPart ← SUBSTRING(Name, 2, 4)
3Take the 4 characters of Name that begin at position 2 and store them in Part		CReturns one character: the character at position 3 of Word, as a string
4Output the first character of Name by extracting one character from the start		DOUTPUT SUBSTRING(Name, 1, 1)
5SUBSTRING("Happy Days", 5)		ESUBSTRING always returns a string, so it cannot be assigned to an INTEGER variable.
6Letter: INTEGER Letter ← SUBSTRING(Word, 1, 1)		FThe length argument is missing. SUBSTRING needs three arguments: the string, the start and the length.

Definitions

SUBSTRING(<string>, <start>, <length>)

Fill in the Blanks

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

Part ← _________("Happy Days", 1, 5)

OUTPUT SUBSTRING("Happy Days", _, 4)

Name ← "Happy Days" Part ← SUBSTRING(Name, 1, _)

Letter ← SUBSTRING("Happy Days", 7, _)

DECLARE Part : ______ Part ← SUBSTRING("Happy Days", 1, 5)

Spot the Error

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

Question 1

A DECLARE Word : STRING

B DECLARE Part : STRING

C Word ← "Happy Days"

D Part ← SUBSTRING(Word, 5, 1)

E OUTPUT Part

Question 2

A DECLARE Letter : STRING

B Name ← "Cambridge"

C Letter ← SUBSTRING(Name, 0, 1)

D OUTPUT Letter

Question 3

A Text ← "IGCSE 0478"

B Code ← SUBSTRING[Text, 7, 4]

C OUTPUT Code

Question 4

A Word ← "Computer"

B Part ← SUBSTRING(Word, 1, -3)

C OUTPUT Part

Question 5

A DECLARE Word : STRING

B DECLARE Part : INTEGER

C Word ← "Happy Days"

D Part ← SUBSTRING(Word, 7, 4)

E OUTPUT Part

Answer Key

SUBSTRING: extracting part of a string

Section A: Quick Questions

A — "Happy"

A — How many characters to take

B — SUBSTRING("Science", 3, 1)

B — "i"

A — STRING, even though it is one character

Section B: Match the Pairs

SUBSTRING("Happy Days", 1, 5) → Returns "Happy": 5 characters taken from position 1

SUBSTRING(Word, 3, 1) → Returns one character: the character at position 3 of Word, as a string

Take the 4 characters of Name that begin at position 2 and store them in Part → Part ← SUBSTRING(Name, 2, 4)

Output the first character of Name by extracting one character from the start → OUTPUT SUBSTRING(Name, 1, 1)

SUBSTRING("Happy Days", 5) → The length argument is missing. SUBSTRING needs three arguments: the string, the start and the length.

Letter: INTEGER Letter ← SUBSTRING(Word, 1, 1) → SUBSTRING always returns a string, so it cannot be assigned to an INTEGER variable.

Section C: Definitions

SUBSTRING(<string>, <start>, <length>) — Returns part of a string: length characters taken from the start position. SUBSTRING("Happy Days", 1, 5) gives "Happy". The result is always a string.

Section D: Fill in the Blanks

Part ← SUBSTRING("Happy Days", 1, 5)

OUTPUT SUBSTRING("Happy Days", 7, 4)

Name ← "Happy Days"
Part ← SUBSTRING(Name, 1, 5)

Letter ← SUBSTRING("Happy Days", 7, 1)

DECLARE Part : STRING
Part ← SUBSTRING("Happy Days", 1, 5)

Section E: Spot the Error

D — The start and length are swapped. This takes 1 character from position 5, which gives "y". To get "Happy" it must start at 1 and take 5 characters: SUBSTRING(Word, 1, 5).

C — Positions in Cambridge pseudocode start at 1, so a start of 0 is not valid. The first character is taken with SUBSTRING(Name, 1, 1).

B — SUBSTRING is a function, so its arguments go inside round brackets ( ), not square brackets. It should be SUBSTRING(Text, 7, 4).

B — The length must be a positive integer because you cannot take a negative number of characters. It should be SUBSTRING(Word, 1, 3), which gives "Com".

B — SUBSTRING always returns a string, so the variable that stores the result must be declared as STRING, not INTEGER.