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.
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.
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.