VMS Help PASCAL, Input Output, Seq Access Output  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The sequential access output procedures apply primarily to files
  opened for sequential access; but can also be used on direct and
  keyed access files.

1 - EXTEND

  The EXTEND procedure opens an existing file, positions the  file
  buffer  after  the  last component, and prepares it for writing.
  It is commonly used to append to a file.

  Syntax:

     EXTEND( file_variable [[, file_name]]
             [[, ERROR := error-recovery]] );

  The 'file_variable' is the name of the file variable  associated
  with the output file.

  The 'file_name' is the name of the file to  be  associated  with
  the  'file_variable'.   If  the  file  was  opened with the OPEN
  procedure, the 'file_name' is ignored.

  The 'error-recovery' is the action  to  be  taken  if  an  error
  occurs during execution of the routine.

  The file can be in any mode before EXTEND is called to  set  the
  mode  to generation.  If the file is an external file and is not
  already open, EXTEND opens it using the defaults  for  the  OPEN
  procedure.

  After execution of EXTEND, the file is positioned after the last
  component,  and  EOF  and UFB return TRUE.  If the file does not
  exist, EXTEND does not create it, but returns an  error  at  run
  time.

  A call to EXTEND on a relative file  opened  for  direct  access
  positions the file after its last existing component.

  A call to EXTEND on an indexed file opened for random access  by
  key  positions the file after the last component relative to the
  primary key.

  See the "Compaq Pascal Language Reference Manual" for a complete
  description of the EXTEND procedure.

2 - PUT

  The PUT procedure adds a new component to a file.

  Syntax:

     PUT( file_variable [[, ERROR := error-recovery]] );

  The 'file_variable' specifies the  name  of  the  file  variable
  associated with the output file.

  The 'error-recovery' is the action  to  be  taken  if  an  error
  occurs during execution of the routine.

  Before executing the first PUT procedure on a  file  opened  for
  sequential  access,  you  must  execute  an  EXTEND,  REWRITE or
  TRUNCATE procedure to set the file to generation mode.   EXTEND,
  REWRITE  and  TRUNCATE  set EOF to TRUE, thus preparing the file
  for output.  (TRUNCATE is legal only on  files  with  sequential
  organization.)   If  the  file  has  indexed  organization,  the
  components to be written must be ordered by the primary key.

  Before executing the first PUT statement on a  file  opened  for
  direct  access,  you  must  execute an EXTEND, REWRITE or LOCATE
  procedure to position the file.

  The PUT procedure writes the value of the file  buffer  variable
  at  the  end  of  the specified sequential-file or direct-access
  file.  You can use LOCATE to position a direct-access  file  and
  then  use  PUT to write the value of the file buffer variable at
  that position.  After execution of the PUT procedure, the  value
  of  the  file  buffer  variable  becomes  undefined (UFB returns
  TRUE).  EOF remains TRUE and  the  file  remains  in  generation
  mode.

  You  can  call  the  PUT  procedure  for  a  keyed-access  file,
  regardless  of  the  file's  mode  (inspection,  generation,  or
  undefined).  PUT causes the file buffer variable to  be  written
  to  the  file  at  the  position  indicated  by the key.  If the
  component has more than one key, the  file  buffer  variable  is
  inserted  in  each  index  at  the  appropriate location.  After
  execution of PUT, a keyed-access file is in generation mode.

  See the "Compaq Pascal Language Reference Manual" for a complete
  description of the PUT procedure.

3 - REWRITE

  The REWRITE procedure readies a file for output.

  Syntax:

     REWRITE( file_variable [[, file_name]]
              [[, ERROR := error-recovery]] );

  The 'file_variable' is the name of the file variable  associated
  with the output file.

  The 'file_name' is a string expression to be associated with the
  file_variable.   Files  opened  with REWRITE and the 'file_name'
  stay resident on the disk after the program exits.  However,  if
  the  file was opened with the OPEN procedure, the 'file_name' is
  ignored.

  The 'error-recovery' specifies the action  to  be  taken  if  an
  error occurs during execution of the routine.  By default, after
  the first error, the error message is printed and  execution  is
  stopped.

  The file can be in any mode before REWRITE is called to set  the
  mode  to  generation.  If the file variable has not been opened,
  REWRITE creates and opens it using the same defaults as the OPEN
  procedure.

  The REWRITE procedure truncates a file to length zero  and  sets
  EOF and UFB to TRUE.  You can then write new components into the
  file with the PUT, WRITE, and  WRITELN  procedures  (WRITELN  is
  defined   only  for  text  files).   After  the  file  is  open,
  successive calls to REWRITE truncate  the  existing  file  to  a
  length of zero; they do not create new versions of the file.

  To update an existing file  with  sequential  organization,  you
  must   either   use  the  EXTEND  procedure,  use  the  TRUNCATE
  procedure, or copy the contents to another file, specifying  new
  values for the components you need to update.

  When applied to a file with relative  or  indexed  organization,
  REWRITE  deletes  the  contents  of  the  file and sets the file
  position to the beginning of an empty file.

  See the "Compaq Pascal Language Reference Manual" for a complete
  description of the REWRITE procedure.

4 - WRITE

  The WRITE procedure assigns data to an output file.

  Syntax:

     WRITE( [[file_variable, ]]{expression},...
            [[,ERROR := error-recovery]] )

  The 'file_variable' is the name of the file variable  associated
  with  the  output  file.   If you omit the name of the file, the
  default is OUTPUT.

  The 'expression' is an expression whose value is to be  written;
  multiple output values must be separated with commas.  An output
  value must have the same type as the file  components;  however,
  values  written  to  a  TEXT file can also be expressions of any
  ordinal, real, or string type.

  The 'error-recovery' specifies the action  to  be  taken  if  an
  error occurs during execution of the routine.  By default, after
  the first error, the error message is printed and  execution  is
  stopped.

  The file (unless it is a random-access by key file) must  be  in
  generation  mode before WRITE is called; it remains in that mode
  after WRITE has executed.

  By definition, a WRITE statement to a nontext file  performs  an
  assignment  to  the file buffer variable and a PUT statement for
  each output value.  For nontext files, the types of  the  output
  values  must be assignment compatible with the component type of
  the file.

  See the "Compaq Pascal Language Reference Manual" for a complete
  description of the WRITE procedure.