Arrays are great for storing a set of related data items.

We can declare one-dimensional arrays:

DECLARE ages : ARRAY[lb : ub] OF INTEGER

where lb is the lowerbound index (often 1 in pseudocode) and ub is the upperbound index

We can assign data to an array.

ages ← [16,15,18,15,19,12,15,17,12,19]

Now we can process the array. If we are going to process the whole array, use a count-controlled loop:

2-dimensional arrays

2-dimensional arrays also organise a set of related data items, but in a structure that looks like a table or spreadsheet.

We can declare two-dimensional arrays:

DECLARE names : ARRAY[rlb : rub, clb:cub] OF STRING

where:

• rlb is the lowerbound of the row numbers
• rub is the upperbound of the row numbers
• clb is the lowerbound of the column numbers
• cub is the upperbound of the column numbers

We can process a 2D array. If we are going to process the whole array, use a nested count-controlled loop:

Sample Exam Style Question

A 2-dimensional array, colorGrid, stores primary colours, red blue and green.

A sample array of STRINGS might look like this:

Task 1

Write pseudocode to determine which has the highest number of occurences in the grid: red, green or blue.

Task 2

Write pseudocode to solve this problem.

If the first item in the row is red and the last item in a row is red, then the middle item in a row will become red.

Every grid always has 4 rows and5 columns, but there could be any number of rows.

Remember to declare the array as you get started.