Specifications

3
Operating System Routines
This chapter describes the operating system routines that are used by device
drivers and employs the following conventions:
• Most routines reside in modules within the [SYS] facility of the operating
system. A routine description provides a facility name (in brackets) only if
the module is not located in the [SYS] facility.
• Many routines are not directly called by device drivers. Rather, the operating
system supplies macros that drivers invoke to accomplish the routine call.
The description of a routine that has such a macro interface lists the name of
the associated macro. Chapter 2 describes how a driver can use these macros.
• System routines generally return a status value in R0 (for instance,
SS$_NORMAL). The low-order bit of this value indicates successful (1)
or unsuccessful (0) completion of the routine. Additional information on
returned status values appears in the OpenVMS System Services Reference
Manual and the OpenVMS System Messages and Recovery Procedures
Reference Manual.
• If a register is not used to transfer output or is not explicitly indicated as
destroyed, a driver can assume that its contents are preserved.
3–1