This part of ISO/IEC 9945 defines a standard operating system interface and environment to support application portability at the source-code level. It is intended to be used by both application developers and system implementors.
This part of ISO/IEC 9945 comprises four major components:
(1) Terminology, concepts, and definitions and specifications that govern structures, headers, environment variables, and related requirements
(2) Definitions for system service interfaces and subroutines
(3) Language-specific system services for the C programming language
(4) Interface issues, including portability, error handling, and error recovery The following areas are outside of the scope of this part of ISO/IEC 9945:
(1) User interface (shell) and associated commands
(2) Networking protocols and system call interfaces to those protocols
(3) Graphics interfaces
(4) Database management system interfaces
(5) Record I/O considerations
(6) Object or binary code portability
(7) System configuration and resource availability
(8) The behavior of system services on systems supporting concurrency within a single process
This part of ISO/IEC 9945 describes the external characteristics and facilities that are of importance to applications developers, rather than the internal construc-tion techniques employed to achieve these capabilities. Special emphasis is placed on those functions and facilities that are needed in a wide variety of com-mercial applications.
This part of ISO/IEC 9945 has been defined exclusively at the source-code level. The objective is that a Strictly Conforming POSIX.1 Application source program can be translated to execute on a conforming implementation.