OpenVMS Calling Standard

The HP OpenVMS Calling Standard provides the definitive technical specification for procedure-to-procedure calls across the OpenVMS operating system. This document outlines critical run-time requirements, including register usage, stack frame conventions, argument passing mechanisms, and data structure layouts for OpenVMS VAX, Alpha, and Industry Standard 64 (I64) environments. It also covers condition and exception handling, stack unwinding, and signature information necessary for interoperability with translated images. This manual is primarily intended for compiler and debugger implementers and developers building system software.