{
{   The purpose of this request is to build a record header in the}
{ user's buffer_area. The buffer_area may be located within a file opened}
{ with amc$segment access_level or in a space allocated by the program.}
{   The record header built by this request is compatible with one built}
{ using amp$put requests. Thus a file created using this request may}
{ be read by a program which uses amp$get requests or amp$unpack_record_}
{ header.}
{   This request may only be issued for a file opened with amc$segment or}
{ amc$physical access_level.}
{   If this request is issued for a file which does not have a record}
{ header, normal status is returned and the buffer_area variable is}
{ returned unchanged.}
{   This request performs a NEXT in the buffer_area sequence to allocate}
{ space for the record header in the buffer_area. The buffer_area}
{ variable is updated to point to the first byte beyond the record header}
{ in the buffer. If insufficient space exists in the buffer for the}
{ record header a NIL pointer is returned in the buffer_area variable}
{ and abnormal status is returned.}
{
{       AMP$PACK_RECORD_HEADER (FILE_IDENTIFIER, BUFFER_AREA, HEADER, STATUS)
{
{ FILE_IDENTIFIER: (input) This parameter specifies the file access
{       identifier established when the file was opened.
{
{ BUFFER_AREA: (input-output) This parameter specifies the location within}
{       the user buffer at which the record header will be placed. This}
{       request returns the address of the first byte beyond the record}
{       header in the buffer. A NIL pointer and abnormal status are returned}
{       if insufficient space exists in the buffer for the record header.}
{       This request assumes that the record header and the record will be}
{       stored contiguously in the buffer.}
{}
{ HEADER: (input) This parameter specifies the contents of the record}
{       header to be packed into the user's buffer_area. This parameter}
{       must be supplied but will be ignored if the record_type of the}
{       file is one which does not support  a record header.}
{       Not all fields of this parameter are applicable to record types other}
{       than amc$variable; no indication is given if such fields go unused.}
{       This parameter is a record which includes the following fields:}
{        Header_type - specifies type of record header to be written.}
{        Length - specifies the number of bytes of the record described by}
{                 this header.}
{        Previous_length - specifies the number of bytes in the preceding}
{                          record, exclusive of the previous header.}
{        Unused_bit_count - specifies the number of bits in the last byte of}
{                           this record which do not contain valid data.}
{        User_information - specifies a cell whose value is defined by the}
{                           user. This information is stored in the record}
{                           header but its value may only be obtained with}
{                           the amp$unpack_record_header request, i.e. it}
{                           is not returned if the record is read with}
{                           amp$get requests.}
{}
{ STATUS: (output) this parameter specifies the request status.
{       CONDITION:  ame$ring_validation_error,
{       IDENTIFIER: amc$access_method_id.
{
