Mathematica Tutorial: Notebooks And Documents - Wolfram Research

114 Notebooks and DocumentsDefining Output FormatsJust as Mathematica allows you to define how expressions should be evaluated, so also it allowsyou to define how expressions should be formatted for output. The basic idea is that wheneverMathematica is given an expression to format for output, it first calls Format@exprD to find outwhether any special rules for formatting the expression have been defined. By assigning a valueto Format@exprD you can therefore tell Mathematica that you want a particular kind of expressionto be output in a special way.This tells Mathematica to format bin objects in a special way.In[1]:=Format@bin@x_, y_DD := MatrixForm@88x