← IGCSE Computer Science Paper 2

Choosing between CHAR and STRING

Use CHAR for a value that is always exactly one character, like a grade letter or Y/N. Use STRING for text of any length, including none, like a name or phone number.

Part of: IGCSE Computer Science 0478 — 8.1a Data Types and Variables — Module 21

Understanding Choosing between CHAR and STRING in IGCSE Computer Science Paper 2

What it does: Names vary in length (Al, Alexandra), so STRING is needed rather than CHAR. An answer of 'Y' or 'N' is exactly one character, so CHAR is the best choice. A phone number is not used in calculations, and an INTEGER would lose the leading zero. Store it as STRING. A city name such as "Paris" has many characters, so it needs STRING. A grade letter is always a single character, so CHAR is the right data type.

Common mistakes: A phone number is not used in calculations and can start with 0, so it must be STRING. INTEGER would drop the leading zero. It should be DECLARE Phone : STRING. Single quotes make a CHAR literal, which holds exactly one character. A name is a STRING and needs double quotes: Name ← "Sam".

Class: _____________________ · Name: _____________________ · Date: _________

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This module's key terms are also in a printable crossword (Modules 327–336) and word search (Modules 317–336).

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Learning

Duo

Which data type suits a grade letter such as 'B'?

STRINGCHAR

Matches

DECLARE Surname : CHAR

↓

A surname can be many characters long, so it needs STRING, not CHAR. CHAR holds only one character.

Applying

Meanings

Term

CHAR or STRING

Meaning

Use CHAR for a value that is always exactly one character, like a grade letter or Y/N. Use STRING for text of any length, including none, like a name or phone number.

Practice

DECLARE Grade : CHAR

Testing

Gaps

DECLARE Grade :

Check Answer

Spots

1DECLARE Phone : INTEGER

2INPUT Phone

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Quick Questions

1. Which data type suits a grade letter such as 'B'?

A. CHAR ✓

B. STRING

A grade letter is always exactly one character, so CHAR is the best choice.

2. Which data type suits a student's name?

A. STRING ✓

B. CHAR

Names have different lengths, so they need STRING. CHAR holds only one character.

3. Which data type suits a phone number such as "07700900123"?

A. STRING ✓

B. INTEGER

A phone number is not used in calculations, and an INTEGER would lose the leading zero. Store it as STRING.

4. A program asks 'Do you want to continue? (Y/N)'. Which type stores the answer?

A. STRING

B. CHAR ✓

The answer is always one character, 'Y' or 'N', so CHAR fits.

5. Which statement is true?

A. A CHAR can hold any length of text, including none

B. A STRING can hold any length of text, including none ✓

Only STRING can be any length, even empty (""). CHAR is always exactly one character.

Match the Pairs

DECLARE Grade : CHAR → Grade holds exactly one character, such as a grade letter like A, B or C

DECLARE PhoneNumber : STRING → PhoneNumber holds text of any length; digits are stored as text because they are not used in calculations

A name can be any length, so it should be stored as a STRING → DECLARE FirstName : STRING

A yes or no answer of 'Y' or 'N' is always one character, so it is a CHAR → DECLARE Answer : CHAR

DECLARE Surname : CHAR → A surname can be many characters long, so it needs STRING, not CHAR. CHAR holds only one character.

DECLARE Grade : STRING Grade ← "A" → A grade letter is always exactly one character, so CHAR is the better choice. The CHAR literal would also use single quotes: 'A'.

Key Term

CHAR or STRING

Use CHAR for a value that is always exactly one character, like a grade letter or Y/N. Use STRING for text of any length, including none, like a name or phone number.

Fill in the Blanks

1. DECLARE Grade : CHAR Grade ← 'B'

Hint: Type the data type for a value that is always exactly one character, like a grade letter.

2. DECLARE FirstName : STRING FirstName ← "Priya"

Hint: Type the data type for a name, which can be any number of characters.

3. DECLARE PhoneNumber : STRING PhoneNumber ← "07700900123"

Hint: Type the data type for a phone number. It is never used in calculations and has many digits.

4. DECLARE Answer : CHAR OUTPUT "Continue? (Y/N)" INPUT Answer

Hint: Type the data type for a reply that is always a single letter, either Y or N.

5. DECLARE Comment : STRING Comment ← ""

Hint: Type the data type that can hold text of any length, including no characters at all.

Spot the Error

Question 1

A DECLARE Phone : INTEGER

B INPUT Phone

C OUTPUT Phone

Line A — A phone number is not used in calculations and can start with 0, so it must be STRING. INTEGER would drop the leading zero. It should be DECLARE Phone : STRING.

Question 2

A DECLARE Grade : CHAR

B Grade ← 'B'

C DECLARE Name : STRING

D Name ← 'Sam'

Line D — Single quotes make a CHAR literal, which holds exactly one character. A name is a STRING and needs double quotes: Name ← "Sam".

Question 3

A DECLARE Answer : CHAR

B Answer ← "Yes"

C OUTPUT Answer

Line B — A CHAR holds exactly one character, and "Yes" is a three-character STRING. For a Y/N answer use the single character 'Y'.

Question 4

A DECLARE Surname : STRING

B Surname ← ""

C Initial ← ''

Line C — A CHAR must be exactly one character, so it cannot be empty. Only a STRING can be empty. It should be Initial ← 'K' with one character between the quotes.

Question 5

A DECLARE FirstName : CHAR

B INPUT FirstName

C OUTPUT FirstName

Line A — A name can be any length, so it needs STRING. A CHAR can only hold one character. It should be DECLARE FirstName : STRING.

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