5 PRINT "INPUT KNOWN POINTS (X1,Y1,X2,Y2,CARRIAGE RETURN)"
10 INPUT X1,Y1,X2,Y2  
15 PRINT 
20 PRINT "INPUT X-COORD. OF PT. TO BE INTERPOLATED. TO END "  
25 PRINT "PR0GRAM INPUT 99999." 
30 INPUT X 
35 IF X=99999 THEN 99
40 PRINT "Y=";Y1+(Y2-Y1)/(X2-X1)*(X-X1)
45 PRINT 
50 PRINT "X"; 
55 GOTO 30  
99 END 

