TI-83
Func
On a TI calculator you can use function graphic mode
MODE ▼ ▼ ▼
or via the CATALOG as
CATALOG ⎵ 2nd 0 ►Func ENTER
Explanation
You can store up to 10 functions to the function variables Y1 through Y9, and Y0.
Example 1
To change to graph mode Func
CATALOG ⎵ 2nd 0 ►Func ENTER Func ENTER Func Done