# TI-82/83/85/86 Mathematics Use

### Contents

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The TI-82, TI-83, TI-85 and TI-86 are graphing calculators designed by Texas Instruments. The TI-85 was the first and the TI-82 was introduced as a simpler and less expensive version of the TI-85. Since then, the TI-85 has been replaced by an improved calculator called the TI-86, and the TI-82 has been replaced by first the TI-83, then the TI-83+ and now the TI-84. These calculators are bracketed by the less sophisticated TI-73 and TI-80 and the much more powerful TI-89 and TI-92, which have full symbolic algebra systems on them. These notes apply only to the TI-82/83/85/86, to which I have had various amounts of access. In particular I don't know if my notes apply to the TI-89/92, to which I have had no immediate access.

This series of calculators are all based on the Zilog Z80 chipset, well known from its use in a variety of early PCs in the late 70's and early 80's. They can be effectively programmed in Z80 Assembly, but we will concentrate on non-programming use and some simple programming in the BASIC language, also supported by the calculators.

## 1. General Use of TI Graphing Calculators

### The Basics - Home Screen

Most of the action takes place in what is called the "Home Screen". This is the screen where you do arithmetic, issue BASIC commands and view results. If you type [2][+][2][ENTER] and see an answer of 4 you are on the Home Screen. From any other mode you can reach the home screen by pressing the [EXIT] button, if necessary several times.

Each key has three possible meanings. If you just press that key the character printed in white on the key is entered. If you press the yellow [2nd] key (top left corner of the keyboard) then a key the effect will be that printed in yellow above the key. If you press the blue [ALPHA] key then a key the effect will be that printed in yellow above the key. For example:

• [7] - Types the digit "7"
• [2nd][7] - Shows the Matrix menu. We will write this as [MATRX], as though it were a single key.
• [ALPHA][7] - Types the capital letter "L". We will write this combination as [L], as though it were a single key.
• [2nd][ALPHA][7] - Types the lower case letter "l". We will write this combination as [L], as though it were a single key.
Pressing the blue [ALPHA] key twice sets the ALPHA-lock, so you can type several letters in succession. Pressing the [ALPHA] key again unsets ALPHA-lock.

When entering an expression on the Home Screen you can edit it with the following keys:

• [<] and [>] (left and right arrows) - move backwards and forwards within the expression.
• [DEL] - Delete (erase) the character you are over.
• [CLEAR] - Clear the line you are working on.
• [ENTRY] - Replace the line you are working on with the last expression you executed.
• [INS] - Enter insert mode. When the cursor is an underline, rather than a block, what you type pushes existing text to the right, rather than being written over it.

The results of the preceding computation can be used in an expression by typing the [Ans] key (i.e. [2nd][(-)]).

### Other Modes/Screens

Other modes or screens can be reached by typing the appropriate key. These other screens can either take over the entire screen or merely add a menu across the bottom of the screen. When in a mode you can always return to the Home Screen by pressing the [EXIT] key, if necessary several times. Some modes are:

• [MATRX] - Matrix mode. In this mode you can edit matrices with a full-screen graphical editor and enter matrix commands.
• [PRGM] - Programming mode. In this full-screen mode you can create, edit, save and run BASIC programs.
• [GRAPH] - Graphing mode. Graph mode takes over the entire screen.

When a mode has a menu items on the menu are selected by pressing one of the buttons directly below the screen, [F1] through [F5]. For example (at least on the TI-85/86) enter Matrix mode by pressing the [MATRX] key. Note the menu at the bottom of the screen. Select the third menu item, "MATH" by pressing the [F3] key. A new menu appears with Matrix Math operations.

### Help on TI Calculators

The calculator has no on-line help, so the only reference you get with it is the manual. The manual is a perfectly satisfactory reference for basic use and the commands used in programming, but it doesn't go beyond that. Some other sources of information are:

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Robert Campbell
8 October, 2001