TI-84 Programming: A Beginner's Guide to TI-BASIC

Most students use the TI-84 as a sophisticated calculator, but it's also a programmable computer. TI-BASIC, the built-in programming language, lets you write programs that automate repetitive calculations, create interactive problem-solvers, and even build simple games. And unlike modern programming languages, you don't need a laptop or internet connection, just your calculator.

This guide teaches you TI-BASIC from scratch, even if you've never written a line of code before.

Why Learn TI-BASIC?

• Automate calculations, Write a program once and reuse it for every problem of that type.
• Learn programming fundamentals, Variables, loops, and conditionals are the same concepts in every language.
• Build useful tools, Quadratic formula solvers, unit converters, and statistics tools you'll actually use.
• Impress your teacher, There's something undeniably cool about showing a program running on your calculator.

Accessing the Program Editor

To create a new program:

1. Press PRGM to open the program menu.
2. Arrow right to NEW and press ENTER.
3. Type a name for your program (letters only, up to 8 characters) and press ENTER.
4. You're now in the program editor, with a blinking cursor on the first line.

To run a program you've already created, press PRGM → EXEC, select your program, and press ENTER twice.

Your First Program: Hello World

Let's write the classic "Hello World" program. In the editor:

Here's what each line does:

• ClrHome, Clears the calculator's home screen before displaying output.
• Disp, Displays text or a value on the screen. Strings must be in quotes.

To enter ClrHome, press PRGM → I/O → 8: ClrHome. To enter Disp, press PRGM → I/O → 3: Disp. Quotes are accessed via ALPHA → +.

Variables in TI-BASIC

TI-BASIC has 27 single-letter variables: A through Z, plus θ (theta). You assign a value to a variable using the store arrow (STO→):

Getting User Input with Prompt and Input

Programs become much more useful when they accept user input. TI-BASIC offers two input commands:

Access Prompt via PRGM → I/O → 2: Prompt and Input via PRGM → I/O → 1: Input.

Program: Quadratic Formula Solver

Here's a genuinely useful program, a quadratic formula solver that finds both roots of ax² + bx + c = 0:

This program introduces three new concepts: If/Then/Else/End for conditionals, the discriminant check for real roots, and the quadratic formula itself expressed in TI-BASIC syntax.

Conditionals: If, Then, Else, End

TI-BASIC's conditional structure is:

Comparison operators: = (equality), ≠, >, <, ≥, ≤. Access these via 2ND → MATH (TEST).

For a single-line conditional without Else (if true, execute one line; otherwise skip it), you can write it on one line without Then/End:

Loops: For, While, Repeat

TI-BASIC supports three loop types:

For Loop, run a fixed number of times

While Loop, run while a condition is true

Repeat Loop, run until a condition becomes true

Program: Factorial Calculator

Here's a clean program that calculates N! (N factorial) using a For loop:

Useful Built-In Commands

• ClrHome, Clear the home screen.
• Disp, Display text or values.
• Output(row, col, value), Display at a specific screen position.
• Pause, Pause execution until ENTER is pressed.
• Stop, End the program immediately.
• Menu(, Create an interactive menu with selectable options.
• getKey, Detect which key the user is pressing (for games).

Debugging Tips

When your program has an error, the TI-84 shows an error message and offers to Goto the problematic line. Common errors:

• ERR:SYNTAX, A command is typed incorrectly or missing a closing parenthesis.
• ERR:UNDEFINED, You're using a variable that hasn't been given a value yet.
• ERR:DIVIDE BY 0, Division by zero in your code. Add an If check before dividing.
• ERR:DOMAIN, An argument is outside the valid range (e.g., √ of a negative number).

Where to Find More TI-BASIC Programs

The TI-BASIC community has thousands of free programs available. Websites like ticalc.org host programs for games, math, science, and more. You can also transfer programs to your TI-84 using TI Connect CE software (free download from Texas Instruments).