Difference Quotient - TI 89 or TI 92

This program estimates the value of a derivative at a point using the difference quotient   $f^\prime(A)\approx{f(A+H)-f(A)\over H}$
If you have not used one of the programs posted on this website before, you should read through the information in the Intro to Programming section first.

If you have a TI Connectivity Cable, you can download the program main.diffq.89p

The Program
:diffq( ) {This will already appear if you named the program diffq}
:Prgm {This will already appear}
:ClrIO {ClrIO is in the CATALOG menu}
:Lbl p {Lbl is in the CATALOG menu}
:Local a,h {Local is in the F4 menu}
:Input "a=", a {Input is in the F3 menu} { "  is on the  1 button}
:Input "h=", h
:(y1(a+h) - y1(a))/h$\to$ {y1 is the Y button followed by a 1} {$\to$ is STO}
:Disp "estimate", d  {Disp is in F3 menu}
:Goto p {Goto is in CATALOG menu}
:EndPrgm {This will already appear}

Running the Program
You will need to enter a function f(x) into y1 before running the program. To test the program try the following:
f(x)  =  x3,   a=2,   h=0.01.
The answer should be 12.0601