Find the defects before delivery.
One of the strongest indications of the quality of a piece of software is the number of defects found when it is used. In software, defects are generated by a flaw that causes the code to fail to perform as required. Even in organizations that don’t spend the time and effort to collect information on defects before the software is delivered collect information on defects that crop up after delivery. Four classic defect measures are used “post” delivery. Each of the four measures is used to improve the functional, structural and process aspects of software delivery. They are:
Software Process and Measurement 