HOW TO MAKE A COUNTDOWN (IN SECONDS) ON A TI-83(+) ?

In order to make a countdown (in seconds), you just have to overlap 2 for commands
:Clrhome.....................To clear the screen text
:For(X,1,10)...............The X variable starts at 1 and finish at 10
:For(Y,1,90)...............Like to precedent loop, but this one is just to weight the other
:Output(3,3,10-X)......Display this value : 10-X to create the countdown effect
:End............................End of the First loop
:End............................End of the second loop

You can change the value of the first loop, but you must change the value of the subtraction 10-X too (at the line :Output(4,8,X-10) and you must put the same value than in the loop. But you mustn't change the value of the second loop, it define what a second is.

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