50 REM Hyperbola Contour by Chris Cytera
100 PROTECT BLACK
110 CLS 
120 FOR X=-128 TO 127
130   FOR Y=-124 TO 123
140     INK (X*X+(X-Y)*Y) DIV 100
150     DOT X+128,Y+124
160   NEXT Y
170 NEXT X
180 LET A$=GET$
190 RUN
