5 ONERRORGOTO900
20 MODE8:DIM:a=0:b=0:h=0:c$=CHR$(5)
30 CLS:PRINT"πh(3a²+3b²+h²)/6 a:b:radius";
40 s$="a":z=a:GOSUB500:a=z
41 s$="b":z=b:GOSUB500:b=z
42 CLS:PRINT"πh(3a²+3b²+h²)/6 h:height";
43 s$="h":z=h:GOSUB500:h=z
50 LOCATE0,1:PRINTc$;"Volume =";PI*h*(3*a^2+3*b^2+h^2)/6;:z$=INPUT$(1,@):GOTO30
500 LOCATE0,1:PRINTc$;s$;"=";z;"?";:INPUT@42;z:LOCATE0,0:IFz<0 THEN500 ELSERETURN
900 IFERR=1 THENCLS:ONERRORGOTO0
910 IFERL=500 THENRESUME500
930 LOCATE0,1:PRINTc$;"not found";:z$=INPUT$(1,@):RESUME30