TI 81 Limit Program

Limit of a function at a point C

Prgm :LIMIT
:10000 -> P
:-10000 -> Q
:0 -> N
:.000000001 -> E
:Disp"ENTER C"
:Input C
:.1 -> D
:Lbl 1
:C+D -> X
:If abs(Y1 - P) < E
:Goto 6
:Y1 -> P
:C - D -> X
:If abs(Y1 - Q) < E
:Goto 7
:Y1 -> Q
:D*.1 -> D
:1+N -> N
:If N >  12
:Goto 5
:Goto 1
:Lbl 5
:Disp "AFTER 12 APPROXIMATIONS NO LIMIT"
:Goto 9
:Lbl 6
:Disp"RIGHT LIMIT"
:Disp P
:Disp"LEFT LIMIT"
:Disp Q
:If abs(P - Q) >  10
:0*E
:Goto 4
:(p + Q)/2 -> W
:Disp"LIMIT IS"
:Disp W
:Goto 9
:Lbl 4
:Disp"RIGHT AND LEFT LIMITS DIFFER OR ONE DOES NOT EXIST.  NO LIMIT"
:Lbl 9
:End