This is the code for the conic grapher.  This code was made by Stephen
Dalton.  

":" denotes the beginning of a new line; all non-boolean operators can
be found on the "PRGM" menu of Texas Instruments graphing calculators.

The Y variables can be found on the "VARS" menu under "Y-VARS"/
"FUNCTIONS"

"" Denotes a storage of a variable; it is not an inequality sign.

"sqrt" denotes a sqaure root; just put it in using the second function 
of the "x" button on your calculator.

Okay, let's get started...

PROGRAM:CONIC
:DelVar Y1
:DelVar Y2
:DelVar Y3
:DelVar Y4
:DelVar Y5
:DelVar Y6
:DelVar Y7
:DelVar Y8
:Delvar Y9
:DelVar Y0
:ClrHome
:Output(2,2,"CONIC GRAPHING"0
:Output(4,8,"BY")
:Output(6,2,"STEPHEN DALTON")
:Pause
:ClrHome
:Menu("SECTION","PARABOLA",A,"CIRCLE",B,"ELLIPSE",C,"HYPERBOLA",D)
:Lbl A
:ClrHome
:Menu("DIRECTRIX","(X-H)=4P(Y-K)",E,"(Y-K)=4P(X-H)",F)
:Lbl E
:ClrHome
:Disp "(X-H)=4P(Y-K)"
:Prompt H,P,K
:Graphstyle(1,1)
:"(((X-H))/4P)+K"Y1
:DispGraph
:Pause
:Stop
:Lbl F
:ClrHome
:Disp "(Y-K)=4P(X-H)"
:Prompt K,P,H
:GraphStyle(1,1)
:GraphStyle(2,1)
:"sqrt(4P(X-H))+K"Y1
:"-sqrt(4P(X-H))+K"Y2
:DispGraph
:Pause
:Stop
:Lbl B
:ClrHome
:Menu("FORMAT","X+Y+DX+EY+F",G,"(X-H)+(Y-K)=R",H")
:Lbl G
:Disp "X+Y+DX+EY+F"
:Prompt D,E,F
:-FA
:(D/2)B
:(E/2)C
:BD
:CE
:A+D+EF
:"sqrt(F-(X-B)+C"Y1
:"-sqrt(F-(X-B)+C"Y2
:GraphStyle(1,1)
:GraphStyle(2,1)
:DispGraph
:Pause
:Stop
:Lbl H
:ClrHome
:Disp "(X-H)+(Y-K)=R"
:Prompt H,K,R
:"sqrt(R-(X-H))+K"Y1
:"-sqrt(R-(X-H))+K"Y2
:GraphStyle(1,1)
:GraphStyle(2,1)
:DispGraph
:Pause
:Stop
:Lbl C
:Disp "(X-H)/A+(Y-K)","/B=1"
:Prompt H,A,K,B
:"(sqrt(AB-B(X-H))/A)+K"Y1
:"-(sqrt(AB-B(X-H))/A)+K"Y2
:GraphStyle(1,1)
:GraphStyle(2,1)
:DisGraph
:Pause
:Stop
:Lbl D
:Menu("FORMAT","PARALLEL TO Y",I,"PARALLEL TO X",J)
:Lbl I
:ClrHome
:Disp "(Y-K)/A-(X-H)","/B=1"
:Prompt K,A,H,B
:"(sqrt(AB+A(X-H))/B)+K"Y1
:"-(sqrt(AB+A(X-H))/B)+K"Y2
:"(A/B)(X-H)+K"Y3
:"(-A/B)(X-H)+K"Y4
:GraphStyle(1,1)
:GraphStyle(2,1)
:GraphStyle(3,7)
:GraphStyle(4,7)
:DispGraph
:Pause
:Stop
:Lbl J
:ClrHome
:Disp "((X-H)/A)-((Y-","K))/B=1"
:Prompt H,A,K,B
:"(sqrt(B(X-H)-AB)/A)+K"Y1
:"(-sqrt(B(X-H)-AB)/A)+K"Y2
:"(B/A)(X-H)+K"Y3
:"(-B/A)(X-H)+K"Y4
:GraphStyle(1,1)
:GraphStyle(2,1)
:GraphStyle(3,7)
:GraphStyle(4,7)
:DispGraph
:Pause
:Stop



That's it.  Note: some of the ellipses/circles/hyperbolas will not
completely close.  Just use your imagination.

Tip: After graphing, set zoom factor to "ZFit" to see your graph 
(sometimes) more effectively.

This program took me several hours to write.  Please do not modify it
in any way (yes that includes deleting the title screen; all you have
to do to skip it is press enter) at all without permission from me.  
Not like I'll take legal action or anything, but I just would like to
be informed when a piece of software that I created is going to be 
modified, and would like for such modifications to require my
permission before proceeding.  You can, however, give it to as many 
people as you like, and give them the source code if they don't have a 
TI-83+ so they can use it.  Just PLEASE give them the same junk about 
not modifying it.

Well, now that we're done with all that junk, load this program onto
your calculator right now!