astadr

    OpenVMS usage:ast_procedure
    type:         procedure value
    access:       call without stack unwinding
    mechanism:    by 32- or 64-bit reference
    AST service routine to be executed. On Alpha and Integrity server
    systems, the astadr argument is the 32- or 64-bit address of this
    routine.

 astprm

    OpenVMS usage:user_arg
    type:         quadword (unsigned)
    access:       read only
    mechanism:    by 64-bit value
    AST parameter to be passed to the AST routine specified by the
    astadr argument. On Alpha and Integrity server systems, the
    astprm argument is a quadword value containing this parameter.

 acmode

    OpenVMS usage:access_mode
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Access mode for which the AST is to be declared. The most
    privileged access mode used is the access mode of the caller. The
    resultant mode is the access mode for which the AST is declared.