Christ Preparatory Academy

                    Mr. Rives / Pre calculus

                Programming Exercise #1 (Sept 7th, 2005)

In this exercise we will create a program that displays the value of a variable.  A TI-83 variable is like a variable in algebra, it can hold any value and the value can change.  In this example, we are going to use the variable called X, and we are going to put values into X that stand for a person's age.  Then we are going to display that value whenever our program runs.

This program is obviously concocted and trivial, its main purpose is to get you used to 1) entering a program, 2) running programs, 3) thinking about variables and 4) displaying output from a BASIC program.

Let's Get Started!

Step 1. From the home screen (by which I mean the default screen when the TI-83 starts), Press the [PRGM] button on your TI-83, and this will bring up the EXEC EDIT NEW menu. From there, arrow over and select the NEW menu option:

You will be placed at a prompt where you can enter a name; the screen will show "Name= ", and is waiting for you to type a name.  The name for our sample program is called "AGE".  You will be able to type the word by using the green alphabet letters that are above each key -- 'A' is above the [MATH] key, 'G' is above the [TAN], and 'E' is above the [SIN].

Press [ENTER] after typing the name, and you will be taken to the place where we type in the program:

We are in edit-mode (that's my own phrase, I use it to designate being at the place where we can enter instructions -- and I will use it throughout these tutorials).  Now we are going to enter our first instruction.  Our program is going to do one thing only.  It is going to display the value of a variable.  To select the command to display text on the screen, press the now familiar [PRGM] button, and arrow over to the I/O menu option:

You will see in this menu that there are lots of commands that we can select from.  Each command is explained in your TI-83 calculator manual.  The command we care about for this exercise is the third one, the "Disp" command -- arrow down to it: 

and press enter:

You are now back in edit-mode, and we can specify what exactly we want to Display.  We want to display some text that describes our variable, then we want to display the value of the variable.   Here is how we do it:

It is a little slow and painful to type all those characters.  The quote mark is the Alpha character associated with the [+] key.  The comma mark is its own key (located above the [7] key).  Press [ENTER] after you type the whole line.

Congratulations, you are finished!  You have created a program that prints the value of X as if that value stood for some "AGE".

To exit edit-mode, press [2nd] Quit -- where Quit is associated with the [Mode] key.  This will take us back to the home screen.

Now press the famous [PRGM] key again, and we will be presented with a menu from which to run our program:

On your own calculator, it is likely that there will be a long list of programs.  On mine, there is only one program -- the one we just made.  Here is what happens when I run it:

Now my program displayed "0" as the AGE.  Your calculator might show something different -- it all depends upon what you have for the value of X.

So that we are all on the same page, let's enter a value for X that will be common among all of our calculators.   To do that, we use the [STO->] button:

Now let's run the program again:

That's it, that's your first program. It's not powerful in the wiz-bang space-invaders sort of way, but it is a program and it is a start -- besides, this is just the first lesson.  One day we are going to be so deep into programming the TI-83 that you will be thankful for the slow and thoughtful progression.

What you need to realize is that there is a concept of "program" on the TI-83, that there is a way for you to write your own, that there is such a thing as a variable (which you can change with the [STO->]) button, and that you can display output to the screen.  That's a lot of stuff packed into a simple lesson.  Learn it well, and expect to be asked about it on the test!

Yours,

Mr. Rives