Although technically a guideline, it was a de facto standard for developing avionics software systems until it was replaced in 2012 by DO-178C.
The Federal Aviation Administration (FAA) applies DO-178B as the document it uses for guidance to determine if the software will perform reliably in an airborne environment,[1] when specified by the Technical Standard Order (TSO) for which certification is sought.
In the United States, the introduction of TSOs into the airworthiness certification process, and by extension DO-178B, is explicitly established in Title 14: Aeronautics and Space of the Code of Federal Regulations (CFR), also known as the Federal Aviation Regulations, Part 21, Subpart O.
The certification authorities require and DO-178B specifies the correct DAL be established using these comprehensive analyses methods to establish the software level A-E. Any software that commands, controls, and monitors safety-critical functions should receive the highest DAL - Level A.
Therefore, DO-178B central theme is design assurance and verification after the prerequisite safety requirements have been established.
The number of objectives to be satisfied (eventually with independence) is determined by the software level A-E.
This objective-based nature of DO-178B allows a great deal of flexibility in regard to following different styles of software life cycle.
The flexible nature of DO-178B's processes and entry/exit criteria make it difficult to implement the first time, because these aspects are abstract and there is no "base set" of activities from which to work.
This can be difficult the first time a company attempts to develop a civil avionics system under this standard, and has created a niche market for DO-178B training and consulting.
For a generic DO-178B based process, a visual summary is provided including the Stages of Involvement (SOIs) defined by FAA on the "Guidance and Job Aids for Software and Complex Electronic Hardware".
Typically a Designated Engineering Representative (DER) reviews technical data as part of the submission to the FAA for approval.