System Architecture

• Layout of virtual address space
• Access modes
• Location of OpenVMS callable routines

Calling procedures

• OpenVMS procedure calling standard
• Calling routines
• Passing arguments
• Checking arguments
• Calling supplied OpenVMS routines: RTL (LIB$), RMS$, CLI$, and system services (SYS$)

Synchronizing processes

• Time services (SYS$SETIMR, SYS$BINTIM)
• Events flags: local and common (SYS$WAITFR)
• ASTs
• Lock manager routines (SYS$ENQ, SYS$DEQ)

Accessing devices

• Logical name services (SYS$CRELNM, SYS$TRNLNM)
• Mounting volumes (SYS$MOUNT)
• The QIO system services (SYS$QIO[W])
• Device informational routines (SYS$GETDVI)
• Creating and accessing mailboxes (SYS$CREMBX)

Managing other processes

• Creating detached and subprocesses with and without DCL (SYS$CREPRC, LIB$SPAWN)
• Controlling (other) processes (SYS$SETPRI)
• Scheduling process execution (SYS$HIBER, SYS$WAKE)
• Obtaining process and system information (SYS$GETJPI, SYS$GETSYI)

Building human interfaces (Command Definition Utility – CDU)

• Creating DCL command definitions ($ SET COMMAND)
• Using CLI callbacks (CLI$PRESENT, CLI$GET_VALUE)
• Defining and using DCL foreign commands and DCL$PATH

Communicating between processes

• Using the P1 common area (LIB$PUT_COMMON)
• Accessing DCL symbols in programs (LIB$GET_SYMBOL)
• Private and global sections (SYS$CRMPSC, SYS$MGBLSC)
• Communicating with operators from images (SYS$SNDOPR)

Accessing terminals

• Using the SMG$ routines
• Handling control/C and control/Y routines

Sharing code

• Creating and using shareable images

Handling exceptions and exits

• VAX/Alpha condition handling facility
• Using and defining a condition handler (LIB$ESTABLISH)
• Unwinding the call stack (SYS$UNWIND)
• Declaring and using exit handlers (SYS$DCLEXH)
• Accessing termination mailboxes

Measuring and improving performance

• Obtaining program performance statistics
• (LIB$SHOW_TIMER)
• Modifying the working set size (SYS$ADJWSL)

Using the callable MAIL interface

• Callable MAIL routines (MAIL$)
• Defining item lists for callable MAIL