Reliability is an attribute of any computer-related component (software, or hardware, or a network, for example) that consistently performs according to its specifications. It has long been considered one of three related attributes that must be considered when making, buying, or using a computer product or component. Reliability, availability, and serviceability - RAS, for short - are considered to be important aspects to design into any system. In theory, a reliable product is totally free of technical errors; in practice, however, vendors frequently express a product's reliability quotient as a percentage. Evolutionary products (those that have evolved through numerous versions over a significant period of time) are usually considered to become increasingly reliable, since it is assumed that bug s have been eliminated in earlier releases. For example, IBM's z/OS (an operating system for their S/390 server series), has a reputation for reliability because it evolved from a long line of earlier MVS and OS/390 operating system versions.
The Institute of Electrical and Electronics Engineers ( IEEE ) sponsors an organization devoted to reliability in engineering, the IEEE Reliability Society (IEEE RS). The Reliability Society promotes industry-wide acceptance of a systematic approach to design that will help to ensure reliable products. To that end, they promote reliability not just in engineering, but in maintenance and analysis as well. The Society encourages collaborative effort and information sharing among its membership, which encompasses organizations and individuals involved in all areas of engineering, including aerospace, transportation systems, medical electronics, computers, and communications.