Software quality characteristics

ISO 9126 quality model for external and internal quality (characteristics and sub-characteristics).

Focusing on one external characteristic of software quality can affect other characteristics positively, adversely, or not at all (From "Code Complete 2")

● Correctness. The degree to which a system is free from faults in its

specification, design, and implementation.

● Usability. The ease with which users can learn and use a system.

● Efficiency. Minimal use of system resources, including memory and

execution time.

● Reliability. The ability of a system to perform its required functions under

stated conditions whenever required—having a long mean time between

failures.

● Integrity. The degree to which a system prevents unauthorized or improper

access to its programs and its data. The idea of integrity includes restricting

unauthorized user accesses as well as ensuring that data is accessed

properly—that is, that tables with parallel data are modified in parallel, that

date fields contain only valid dates, and so on.

● Adaptability. The extent to which a system can be used, without

modification, in applications or environments other than those for which it

was specifically designed.

● Accuracy. The degree to which a system, as built, is free from error,

especially with respect to quantitative outputs. Accuracy differs from

correctness; it is a determination of how well a system does the job it’s built

for rather than whether it was built correctly.

● Robustness. The degree to which a system continues to function in the

presence of invalid inputs or stressful environmental conditions.