Characteristics of a quality Software

The ISO 9126-1 Software Quality Model defines 6 main quality characteristics of Software

1. Functionality: Functionality of software defines the functions of the software. It is also considered that all functions of the software are working correctly or not. The components of software do not function/work in isolation. It defines the ability of software components to work together with interacting with each other.
2. Reliability: Reliability ensures that the software is reliable or not, that is the software recovers from the state of failure to the working state, inclusion of data and networks and is also known as fault tolerance.
3. Usability: The usability ensures that the software can be easily operated by the user into the given environment that is it should be easily understandable to the appropriate user and thus it becomes easy to operate and use the software.
4. Efficiency: The efficiency of the software defines how much efficient is the software? That is it gives the correct response in a specified time i.e. transaction rate. It should also make correct use of the available resources and should not use the resources when they are not needed, hence they will be used whenever there is a need to use them otherwise they can sit idle or any other programs may use them.
5. Maintainability:  The Maintainability defines that the software should be able to find the root cause of the failure and have some maintenance features included in the software that makes easy to maintain the software easily by the user and thus the developer help is less needed. This makes the system stable.
6. Portability: Portability ensures that the changes in the operating environment and new specifications may not impact on the software that is the adaptability of the software.