5 ONERRORGOTO900
20 MODE8:DIM:r=0:s=0:h=0:c$=CHR$(5)
30 CLS:PRINT"π(R+r)√(h²+(R-r)²)+π(R²+r²)";
40 s$="r":z=r:GOSUB500:r=z
50 s$="R":z=s:GOSUB500:s=z
60 s$="h":z=h:GOSUB500:h=z
70 LOCATE0,1:PRINTc$;"Surface =";PI*(r+s)*SQR(h*h+(s-r)^2)+PI*(r^2+s^2);:z$=INPUT$(1,@):GOTO40
500 LOCATE0,1:PRINTc$;s$;"=";z;"?";:INPUT@42;z:LOCATE0,0:IFz<0 THEN500 ELSERETURN
900 IFERR=1 THENCLS:ONERRORGOTO0
910 IFERL=500 THENRESUME500
920 LOCATE0,1:PRINTc$;"not found";:z$=INPUT$(1,@):RESUME30