5 ONERRORGOTO900
20 MODE8:DIM:r=0:h=0:c$=CHR$(5)
30 CLS:PRINT"2ãrh+ãar,a=û(h(2r-h))  r:radius";
40 s$="r":z=r:GOSUB500:r=z
45 CLS:PRINT"2ãrh+ãar,a=û(h(2r-h))  h:height";
50 s$="h":z=h:GOSUB500:h=z
60 a=h*(2*r-h):IFa<0 THEN300 ELSEa=SQRa
70 LOCATE0,1:PRINTc$;"Surface =";PI*r*(2*h+a);:z$=INPUT$(1,@):GOTO30
300 LOCATE0,1:PRINTc$;"not found";: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
920 RESUME300