title: DO-248
text: # DO-248
  
  DO-248C, Supporting Information for DO-178C and DO-278A, published by RTCA, Incorporated, is a collection of Frequently Asked Questions and Discussion Papers addressing applications of DO-178C and DO-278A in the safety assurance of software for aircraft and software for CNS/ATM systems, respectively. Like DO-178C and DO-278A, it is a joint RTCA undertaking with EUROCAE and the document is also published as ED-94C, Supporting Information for ED-12C and ED-109A. The publication does not provide any guidance additional to DO-178C or DO-278A; rather, it only provides clarification for the guidance established in those standards. The present revision is also expanded to include the "Rationale for DO-178C/DO-278A" section to document items that were considered when developing DO-178B and then DO-178C, DO-278A, and DO-330, as well as the supplements that accompany those publications (DO-331, DO-332, DO-333).
  
  Corresponding with the releases of DO-178C and DO-278A, the present revision, DO-248C, is an update to the previous revision DO-248B, Report for Clarification of DO-178B "Software Considerations in Airborne Systems and Equipment Certification". While new FAQs and discussion papers have been added, most of the FAQs and discussion papers of DO-248C are carried over from DO-248B. Some of these items have been marked as deleted or updated as the subjects were addressed by the releases of DO-178C, DO-330, supplements, or other publications. An errata section is not included as the release of DO-178C addressed the errata of DO-178B and no DO-178C errata have been published.
  
  Initially, this publication was an annual clarification report, DO-248B (2001) was preceded by DO-248A (2000) and DO-248 (1999).
  
  ## Outline of contents
  
  DO-248C contains the following:
  
  * Rationale for each process objective of DO-178C/DO-278A
  * 84 frequently asked questions (some noted as either deleted, removed or addressed by other publications)
  * 21 discussion papers:
  
     * Verification Tool Selection Considerations
  
     * The Relationship of DO-178B/ED-12B to the Code of Federal Regulations (CFRs) and Joint Aviation Requirements (JARs)
  
     * The Differences Between DO-178A and DO-178B Guidance for Meeting the Objective of Structural Coverage
  
     * Service History Use—Rationale for DO-178C
  
     * Application of Potential Alternative Methods Compliance for Previously Developed Software (PDS)
  
     * Transition Criteria
  
     * Definition of Commonly Used Verification Terms
  
     * Structural Coverage and Safety Objectives
  
     * Certification With Known Software Problems
  
     * Considerations Addressed When Deciding to Use Previously Developed Software (PDS)
  
     * Qualification of a Tool Using Service History (Removed, see DO-330)
  
     * Object Code to Source Code Traceability Issues
  
     * Definitions of Statement Coverage, Decision Coverage, and Modified Condition/Decision Coverage (MC/DC)
  
     * Partitioning Aspects in DO-178C/DO-278A
  
     * Relationship Between Regression Testing and Hardware Changes
  
     * Cache Management
  
     * Usage of Floating-Point Arithmetic
  
     * Service Experience Rationale for DO-278A
  
     * Independence in DO-178C/DO-278A
  
     * Parameter Data Items and Adaptation Data Items
  
     * Clarification on Single Event Upset (SEU) as It Relates to Software
  