invo_context
    OpenVMS usage:invo_context_blk
    type:         structure
    access:       modify
    mechanism:    by reference
    Address of a valid invocation context block.
 pc_copy
    OpenVMS usage:PC value
    type:         quadword
    access:       read
    mechanism:    by reference
    Address of a quadword that contains the PC value to be written to
    the invocation context block.