This page contains some more information about your TI 83/84 Calculator.  Videos on these topics are not available

How do I interrupt a computation or graphing operation?

Whenever you see a vertical bar in the upper right corner of the calculator screen, the calculator is processing some information.  To interrupt, press the "ON" button.

My graph has extra vertical lines.

You're probably graphing a discontinuous function.  In the default graphing style, the calculator plots points and connects them with straight line segments, even when the points shouldn't be connected.  Try drawing the graph using the "dot" style.  Watch the video "Changing a graph style" for more information.

My graph of a rational function is wrong, or the function values in my table are wrong.

Make sure that you have enclosed the entire numerator in parentheses, and that you have similarly enclosed the entire denominator in parentheses.