Arrays

A 1-dimensional array (1D array) is a single row of elements, like a list.

In CIE pseudocode an array is declared with DECLARE, an ARRAY[start:end] size, and a data type:

DECLARE Scores : ARRAY[1:5] OF INTEGER
DECLARE Names  : ARRAY[1:10] OF STRING
DECLARE Flags  : ARRAY[1:3] OF BOOLEAN

• Scores : ARRAY[1:5] OF INTEGER creates an array called Scores with 5 elements (indices 1, 2, 3, 4 and 5), each holding an integer.
• Names : ARRAY[1:10] OF STRING creates 10 string slots.

After declaration, the array exists but the elements have no useful values yet; they need to be assigned.

1-indexed vs 0-indexed

CIE pseudocode is 1-indexed: the first element is at position 1, the last element at position n (where n is the size).

Python is 0-indexed: the first element is at position 0, the last at position n − 1.

Always use 1-indexed in CIE answers unless the question gives an example using a different convention.

Initialising an array with values

Two common ways:

// Assign one element at a time
DECLARE Scores : ARRAY[1:5] OF INTEGER
Scores[1] ← 12
Scores[2] ← 10
Scores[3] ← 5
Scores[4] ← 2
Scores[5] ← 8

// Or assign a whole list in one go
Scores ← [12, 10, 5, 2, 8]

After either of these, Scores contains the five values 12, 10, 5, 2, 8.