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<H1> A.10.2 Text File Management</H1>
<H4 ALIGN=CENTER>Static Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> The only allowed
file modes for text files are the modes In_File, Out_File, and Append_File.
The subprograms given in subclause <A HREF="AA-A-8-2.html">A.8.2</A>
for the control of external files, and the function End_Of_File given
in subclause <A HREF="AA-A-8-3.html">A.8.3</A> for sequential input-output,
are also available for text files. There is also a version of End_Of_File
that refers to the current default input file. For text files, the procedures
have the following additional effects: </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>For the procedures Create and Open: After a file with mode
Out_File or Append_File is opened, the page length and line length are
unbounded (both have the conventional value zero). After a file (of any
mode) is opened, the current column, current line, and current page
numbers are set to one. If the mode is Append_File, it is implementation
defined whether a page terminator will separate preexisting text in the
file from the new text to be written. </LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>2.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Reason: </B>For a file with
mode Append_File, although it may seem more sensible for Open to set
the current column, line, and page number based on the number of pages
in the file, the number of lines on the last page, and the number of
columns in the last line, we rejected this approach because of implementation
costs; it would require the implementation to scan the file before doing
the append, or to do processing that would be equivalent in effect.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>2.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>For similar reasons, there is
no requirement to erase the last page terminator of the file, nor to
insert an explicit page terminator in the case when the final page terminator
of a file is represented implicitly by the implementation. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>For the procedure Close: If the file has the current mode
Out_File or Append_File, has the effect of calling New_Page, unless the
current page is already terminated; then outputs a file terminator.</LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>For the procedure Reset: If the file has the current mode
Out_File or Append_File, has the effect of calling New_Page, unless the
current page is already terminated; then outputs a file terminator. The
current column, line, and page numbers are set to one, and the line and
page lengths to Unbounded. If the new mode is Append_File, it is implementation
defined whether a page terminator will separate preexisting text in the
file from the new text to be written. </LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>4.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Reason: </B>The behavior of
Reset should be similar to closing a file and reopening it with the given
mode</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<DIV Class="Normal"> The exception Mode_Error is propagated by the
procedure Reset upon an attempt to change the mode of a file that is
the current default input file, the current default output file, or the
current default error file. </DIV>
<DIV Class="NotesHeader"><FONT SIZE=-1>NOTES</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<DIV Class="Notes" Style="margin-bottom: 0.4em"><FONT SIZE=-1>22 An
implementation can define the Form parameter of Create and Open to control
effects including the following: </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7</FONT></DIV>
<UL Class="NotesBulleted"><FONT SIZE=-1><LI TYPE=DISC>the interpretation of line and column numbers for an interactive
file, and</LI></FONT></UL>
<DIV Class="Paranum"><FONT SIZE=-2>8</FONT></DIV>
<UL Class="NotesBulleted"><FONT SIZE=-1><LI TYPE=DISC>the interpretation of text formats in a file created by
a foreign program. </LI></FONT></UL>
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