Topics / Programming / 2D Arrays

2D Arrays

2D arrays are data structures capable of storing more than one item of data (value) at a time.

Unlike a 1D array, which is best visualised as a single list of values, a 2D array looks like a table of values.

To achieve this, a 2D array is technically an array which contains further arrays.

The individual values are still called elements, and all elements must be of the same data type.

Example:

The pseudocode to declare a 2D array might look like this:

DECLARE ExamMark : ARRAY[1:10, 1:3] OF INTEGER

Our example array called ExamMark[] has ten elements where we can store three values of the same data type (in this case integers).

Arrays usually start with index numbers of 0 unless intentionally declared otherwise (as above).

Notice how we now need two indexes (i and j) to read or assign values into the array.

ExamMark[]

j
123
i1
2
3
4
5
699
7
8
9
10

To assign or read from a 2D array, we must refer to the array name and both index positions, e.g. ExamMark[6,2] contains 99.

It is common to use variables to represent the index values of a 2D array, e.g. ExamMark[i,j].

When a new value is assigned to an array element, it automatically replaces whatever was stored in that position previously.

Topics / Programming / 2D Arrays

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