Steve McConnell’s Code describes the characteristics of internal and external qualities
1. External Quality Characteristics: Correctness, Usability, Efficiency, Reliability, Integrity, Adaptability, Accuracy, and Robustness.
2. Internal Quality Characteristics: Maintainability, Flexibility, Portability, Re-usability, Readability, Testability, and Understandability.

→ Software quality assurance (SQA) consists of a means of monitoring the software engineering processes and methods used to ensure quality.
→ The ISO quality assurance standard that applies to software Engineering is ISO 9001 : 2000.

Quality control: Quality control involves the series of inspections, reviews, and tests used throughout the software process to ensure each work product meets the requirements placed upon it. Quality control includes a feedback loop to the process that created the work product. The combination of measurement and feedback allows us to tune the process when the work products created fail to meet their specifications.This approach views quality control as part of the manufacturing process.Quality control activities may be fully automated, entirely manual, or a combination of automated tools and human interaction. A key concept of quality control is that all work products have defined, measurable specifications to which we may compare the output of each process. The feedback loop is essential to minimize the defects produced.
Quality Assurance: Quality assurance consists of the auditing and reporting functions of management. The goal of quality assurance is to provide management with the data necessary to be informed about product quality, thereby gaining insight and confidence that product quality is meeting its goals. Of course, if the data provided through quality assurance identify problems, it is management’s responsibility to address the problems and apply the necessary resources to resolve quality issues.