Example Run

Here is a sample run of the program.

Enter the first odometer reading
? 25000
Enter the second odometer reading
? 25300
Enter the first gallons
? 10
Enter the third odometer reading
? 25650
Enter the second gallons
? 11
Your mileage improved by  1.8182  miles per gallon

The above program solves the problem, but it might be nicer if the output were more user friendly. As it is, if the mpg rate goes down with premium gas, the program will print something like:

Your mileage improved by  -2.7121  miles per gallon

It would be nice if the program printed a different message when the rate did not improve. This calls for the two-way decision type of control structure. The QBasic statements for the last task, write out the result could be:

IF IMPROVEMENT >= 0.0 THEN
  PRINT "Your mileage improved by", IMPROVEMENT, " miles per gallon"
ELSE
  PRINT "Your mileage decreased by", -IMPROVEMENT, " miles per gallon"
END IF

Notice what we did: the general description of the final task, write out the result was not changed, but we solved it in a different way than before.