This document is for use by air transport and general aviation equipment and systems developers@ installers and end users. It may be used to support initial Type or Supplemental Type Certification programs (for installation approvals)@ or TSO authorization programs (for equipment approvals)@ or any other approved certification process. This document is also valid with respect to post??modification re??certification of equipment or systems throughout their operational life cycles. This document addresses the major tasks involved in a typical software development program and provides guidance and recommendations for performing these tasks. Specific areas covered are: a. Criticality Categorization (Section 5.0) ?? Describes the categorization of equipment and systems function criticality and provides guidance on category selection. b. Requirements and Procedures for Software Development Section 6.0) ?? Describes techniques and methods whih an applicant for certification may use to plan the overall software development program needed to support the level of criticality to which the equipment or system will be certificated and covers the range of system/software requirements@ development planning and testing from which specific certification packages may be defined. c. Configuration Management and Qua1iy Assurance Disciplines (Section 7.0) ?? Provides configuration management and quality assurance standards@ together with standards for identification of units and systems for control and tracking of changes based upon the established levels of criticality and equipment application. d. Documentation (Section 8.0) Classifies systems and equipment in regulatory agency and end-user terms and describes components of the available documentation package. Recommends documentation to support certification and to be made available to users. The coverage of the software documentation discussed in this document may overlap with that of the documentation described in ATA Specification 102. This document addresses certification and re-certification-related documentation. The ATA specification defines the documentation needed by airlines to support maintenance of digital computer-based equipment and systems. To ensure that all readers have a common understanding of the terms used in this document@ a glossary of terms is provided in Section 4.0. e. Residual Software Error Probabilities During the preparation of this document@ techniques for estimating the post verification probabilities of software errors were examined. The objective was to develop numerical requirements for such probabilities for digital computer based equipment and systems certification. The conclusion reached@ however@ was that currently available methods do not yield results in which confidence can be placed to the level required for this purposes. Accordingly@ this document does not state post verification software error requirements in these terms.