# 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