← IGCSE Computer Science Paper 2

Declaring a 1D array: DECLARE name : ARRAY[l:u] OF type

Declares a 1D array named StudentNames with indexes 1 to 30 (lower:upper), each element holding a STRING. It only sets up the array; no values are stored yet.

Part of: IGCSE Computer Science 0478 — 8.2 Arrays — Module 5

Understanding Declaring a 1D array: DECLARE name : ARRAY[l:u] OF type in IGCSE Computer Science Paper 2

What it does: [1:30] shows the lower bound 1, a colon, then the upper bound 30, all inside square brackets. The DECLARE line only creates the empty array. The second line is a separate assignment that stores the value 15 in element 1. A declaration does not store any values. You must assign values to the elements yourself before using them. The data type comes at the end, after the word OF: ARRAY[l:u] OF type. Cambridge pseudocode uses OF: ARRAY[1:30] OF STRING. AS is not part of this syntax. The numbers 1:7 are the lower and upper bounds (indexes 1 to 7), not stored values. The array has 7 elements, each able to hold a REAL.

Common mistakes: The array was declared with indexes 1 to 5, so index 6 is above the upper bound and is out of range. The line should be G[5] ← 'B'. The lower and upper bounds must be separated by a colon, not a comma. It should be ARRAY[1:7].

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This module's key terms are also in a printable crossword (Modules 439–448) and word search (Modules 439–458).

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Learning

Duo

Which line correctly declares a 1D array of 30 student names (indexes 1 to 30)?

DECLARE StudentNames : ARRAY(1:30) OF STRINGDECLARE StudentNames : ARRAY[1:30] OF STRING

Matches

DECLARE Names : ARRAY(1:30) OF STRING

↓

Round brackets are used instead of square brackets. The bounds must be written as [1:30].

Applying

Meanings

Term

DECLARE StudentNames : ARRAY[1:30] OF STRING

Meaning

Declares a 1D array named StudentNames with indexes 1 to 30 (lower:upper), each element holding a STRING. It only sets up the array; no values are stored yet.

Practice

DECLARE StudentNames : ARRAY[1:30] OF STRING

Testing

Gaps

DECLARE StudentNames : ARRAY[1:30] OF

Check Answer

Spots

3G[2] ← 'C'

4G[6] ← 'B'

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Quick Questions

1. Which line correctly declares a 1D array of 30 student names (indexes 1 to 30)?

A. DECLARE StudentNames : ARRAY(1:30) OF STRING

B. DECLARE StudentNames : ARRAY[1:30] OF STRING ✓

Array bounds go in square brackets [ ], not round brackets. The form is ARRAY[lower:upper] OF type.

2. In ARRAY[1:30], what separates the lower bound from the upper bound?

A. A colon : ✓

B. A comma ,

The lower and upper bounds of a 1D array are separated by a colon, like [1:30]. A comma would be used to separate dimensions in a 2D array.

3. After running DECLARE Scores : ARRAY[1:5] OF INTEGER, what values are stored in the array?

A. None yet - the declaration only sets up the array ✓

B. Five zeros, one in each element

A declaration does not store any values. You must assign values to the elements yourself before using them.

4. Which declaration puts the data type in the correct place?

A. DECLARE Prices : REAL ARRAY[1:10] OF

B. DECLARE Prices : ARRAY[1:10] OF REAL ✓

The data type comes at the end, after the word OF: ARRAY[l:u] OF type.

5. For DECLARE StudentNames : ARRAY[1:30] OF STRING, what is the lower bound?

A. 1 ✓

B. 30

The number before the colon is the lower bound (1). The number after the colon is the upper bound (30).

Match the Pairs

DECLARE Marks : ARRAY[1:25] OF INTEGER → Declares a 1D array called Marks with indexes 1 to 25, so it has 25 elements, each holding an INTEGER

DECLARE Temps : ARRAY[0:6] OF REAL → Declares a 1D array called Temps with indexes 0 to 6, so it has 7 elements, each holding a REAL number

The bounds go inside square brackets with the lower bound first, then a colon, then the upper bound → DECLARE Names : ARRAY[1:30] OF STRING

The declaration only sets up the array and its data type; it does not store any values, so a separate assignment is needed to fill an element → DECLARE Scores : ARRAY[1:10] OF INTEGER Scores[1] ← 15

DECLARE Names : ARRAY(1:30) OF STRING → Round brackets are used instead of square brackets. The bounds must be written as [1:30].

DECLARE Marks : ARRAY[1:20] INTEGER → The word OF is missing before the data type. It should be ARRAY[1:20] OF INTEGER.

Key Term

DECLARE StudentNames : ARRAY[1:30] OF STRING

Declares a 1D array named StudentNames with indexes 1 to 30 (lower:upper), each element holding a STRING. It only sets up the array; no values are stored yet.

Fill in the Blanks

1. DECLARE StudentNames : ARRAY[1:30] OF STRING

Hint: Type the data type that each element holds, since student names are text.

2. DECLARE Scores : ARRAY[1:10] OF INTEGER

Hint: Type the keyword that starts a declaration statement.

3. DECLARE Marks : ARRAY[1:20] OF INTEGER

Hint: Type the symbol that separates the lower bound from the upper bound.

4. DECLARE Temperatures : ARRAY[0:6] OF REAL

Hint: Type the keyword that links the bounds to the data type.

5. // one element for each month DECLARE Rainfall : ARRAY[1:12] OF REAL

Hint: Type the upper bound that gives one element for each month, starting from lower bound 1.

Spot the Error

Question 1

A DECLARE G : ARRAY[1:5] OF CHAR

B G[1] ← 'A'

C G[2] ← 'C'

D G[6] ← 'B'

Line D — The array was declared with indexes 1 to 5, so index 6 is above the upper bound and is out of range. The line should be G[5] ← 'B'.

Question 2

A // T = 7 daily temperatures

B DECLARE T : ARRAY[1,7] OF REAL

C T[1] ← 21.5

D T[2] ← 19.0

Line B — The lower and upper bounds must be separated by a colon, not a comma. It should be ARRAY[1:7].

Question 3

A DECLARE L : ARRAY[1:3] OF CHAR

B L[1] ← 'x'

C L(2) ← 'y'

D L[3] ← 'z'

Line C — Array indexes use square brackets, not round brackets. The line should be L[2] ← 'y'.

Question 4

A DECLARE P : ARRAY[1:9] REAL

B P[1] ← 1.5

C P[2] ← 4.0

Line A — The word OF is missing between the bounds and the data type. It should be DECLARE P : ARRAY[1:9] OF REAL.

Question 5

A // F = 4 fruit initials

B DECLARE F : ARRAY[1:4] OF CHAR

C F[0] ← 'A'

D F[2] ← 'P'

Line C — The lower bound is 1, so index 0 does not exist in this array. The first element is F[1], so the line should be F[1] ← 'A'.

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