PROGRAM:Euler
:FnOff
:Disp "INITIAL X"
:Input x
:DISP "INITIAL Y"
:Input y
:Disp "STEP SIZE"
:Input H
:Disp x
:Disp y
:Lbl P
:Pause
:x+H->U
:y+H*y1->V
:Disp U
:Disp V
:U->x
:V->y
:Goto P

To solve the equation y' = f(x,y), one has to
type in the function y1=f(x,y).