spec_file

    OpenVMS usage:char_string
    type:         character-coded text string
    access:       read-only
    mechanism:    by descriptor
    Specification file name. The spec_file argument is the address
    of a descriptor pointing to the name of a file that contains
    the text of the options requested for the sort or merge. The
    specification file name string and the specification file buffer
    arguments are mutually exclusive.

 spec_buffer

    OpenVMS usage:char_string
    type:         character-coded text string
    access:       read-only
    mechanism:    by descriptor
    Specification text buffer. The spec_buffer argument is the
    address of a descriptor pointing to a buffer containing
    specification text. This text has the same format as the text
    within the specification file. The specification file name
    string and the specification file buffer arguments are mutually
    exclusive.

 context

    OpenVMS usage:context
    type:         longword (unsigned)
    access:       modify
    mechanism:    by reference
    Value that distinguishes between multiple, concurrent SORT/MERGE
    operations. The context argument is the address of a longword
    containing the context value. When your program makes its first
    call to a SORT/MERGE routine for a particular sort or merge
    operation, the context longword must equal zero. SORT/MERGE
    then stores a value in the longword to identify the operation
    just initiated. When you make subsequent routine calls for the
    same operation, you must pass the context value supplied by
    SORT/MERGE.