Square matrices are used (in computer graphics) to represent geometric transformations.

If you sometimes forget whether rows or columns come first,
just remember that matrices are build out
of rowman columns.
A matrix can be given a name.
In printed text,
the name for a matrix is usually a capital
letter in bold face, like **A** or **M**.
Sometimes as a reminder the
dimensions are written to the right of the letter,
as in **B _{3x3}**.

The elements of a matrix also have names,
usually a lowercase letter the same as the
matrix name, with the position of the element
written as a subscript.
So,
for example,
the 3x3 matrix **A** might be written as:

Sometimes you write **A** = [a_{ij}]**A** are named
a_{ij}.