TI-84 Plus Keyboard Basics
The row of keys under the TI-84 Plus calculator screen contains the keys you use when graphing. The next three rows, for the most part, contain editing keys, menu keys, and arrow keys. The arrow keys
control the movement of the cursor. The remaining rows contain, among other things, the keys you typically find on a scientific calculator.
Keys on the calculator are always pressed one at a time; they are never pressed simultaneously. An instruction such as [2nd][ON] indicates that you should first press [2nd] and then press [ON].
Accessing the TI-84 functions in blue
Above and to the left of most keys is a secondary key function written in blue. To access that function, first press [2nd] and then press the key. For example, π is in blue above the [^] key, so to use π in an expression, press [2nd] and then press [^].
Hunting for the function in blue can be tedious. When the [2nd] key is active and the calculator is waiting for you to press the next key, the blinking box cursor symbol is replaced with the up-arrow symbol.
Using the [ALPHA] key to write words
Above and to the right of most keys is a letter written in green. To access these letters, first press [ALPHA] and then press the key. For example, because the letter O is in green above the  key, to enter this letter, press [ALPHA] and then press .
Because hunting for letters on the calculator can be tedious, I tell you the exact keystrokes needed to create them. For example, if I want you to enter the letter O, I say, “Press [ALPHA] to enter the letter O.” Most other books would say “Press [ALPHA][O]” and leave it up to you to figure out where that letter is on the calculator.
You must press [ALPHA] before entering each letter. However, if you want to enter many letters, first press [2nd][ALPHA] to lock the calculator in Alpha mode. Then all you have to do is press the keys for the various letters. When you’re finished, press [ALPHA] to take the calculator out of Alpha mode.
For example, to enter the word TEST into the calculator, press [2nd][ALPHA][SIN][LN] and then press a to tell the calculator that you’re no longer entering letters.
When the calculator is in Alpha mode, the blinking square cursor symbol is replaced with the reversed-A symbol. This symbol indicates that the next key you press will insert the green letter above that key. To take the calculator out of Alpha mode, press [ALPHA].
Using the TI-84 [ENTER] key
The [ENTER] key is used to evaluate expressions and to execute commands. After you have, for example, entered an arithmetic expression (such as 5 + 4), press [ENTER] to evaluate that expression. In this context, the [ENTER] key functions as the equal sign.
Using the variable key
is the key you use to enter the variable in the definition of a function, a parametric equation, a polar equation, or a sequence. In Function mode, this key produces the variable X. In Parametric mode, it produces the variable T; and in Polar and Sequence modes, it produces the following variables:
Using the TI-84 arrow keys
The arrow keys control the movement of the cursor. These keys are in a circular pattern in the upper-right corner of the keyboard. As expected, the right arrow moves the cursor to the right, the left arrow moves it to the left, and so on.
TI-84 keys to remember
The following keystroke and keys are invaluable:
[2nd][MODE]: This is the equivalent of the Escape key on a computer. It gets you out of whatever you’re doing (or have finished doing) and returns you to the Home screen.
[ENTER]: This key is used to execute commands and to evaluate expressions. When evaluating expressions, it’s the equivalent of the equal sign.
[CLEAR]: This is the “erase” key. If you enter something into the calculator and then change your mind, press this key. If you want to erase the contents of the Home screen, repeatedly press this key until the Home screen is blank.