From arrays of numbers to matrices ------------------------------------
Arrays of numbers such as
14−2 035 ,\begin{matrix}1&4&-2\ 0&3&5\end{matrix}\,,
with two rows and three columns, are commonly used in accounting. Such software is known as a spreadsheet program. Such arrays truly become matrices only once addition and multiplication have been defined for them. They are then conventionally enclosed in parentheses, so the array above becomes
(14−2 035).\begin{pmatrix}1&4&-2\ 0&3&5\end{pmatrix}.