There are several ways to enter a function into the TI83 graphing calculator. For basic use, we recommend simply entering a function into the equation editor and then working with it from there. To begin, press Y= to access the equation editor (the Y= menu). The TI83 can accommodate up to 10 functions. 
To enter a function, simply type in the algebraic expression used to define the function. For example, to enter the
quadratic function f defined by , type

Once the function is entered, then you can perform a variety of tasks; for example, evaluate the function at a given input value, graph the function, or make a table of functional values.