10 CLS
20 PRINT "AREA OF A POLYGON" 
30 PRINT 
40 DIM X(25),Y(25) 
50 PRINT "NUMBER OF VERTICES (ENTER 0 TO END PROGRAM)"; 
60 INPUT N 
70 IF N=0 THEN 240  
80 FOR I=1 TO N 
90 IF I>1 THEN 120  
100 PRINT "COORDINATES OF VERTEX";I; 
110 GOTO 130  
120 PRINT "               VERTEX";I; 
130 INPUT X(I),Y(I) 
140 NEXT I 
150 X(N+1)=X(1) 
160 Y(N+1)=Y(1) 
170 A=0 
180 FOR I=1 TO N 
190 A=A+(X(I)+X(I+1))*hY(I)-Y(I+1))
200 NEXT I 
210 PRINT "AREA =";A/2 
220 PRINT 
230 GOTO 50   
240 END