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<H1> A.10.3 Default Input, Output, and Error Files</H1>
<H4 ALIGN=CENTER>Static Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> The following subprograms provide for the control
of the particular default files that are used when a file parameter is
omitted from a Get, Put, or other operation of text input-output described
below, or when application-dependent error-related text is to be output.
</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="Examples"><TT><B>procedure</B> Set_Input(File : <B>in</B> File_Type);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<DIV Class="CodeIndented">Operates on a file of mode In_File. Sets the
current default input file to File.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<DIV Class="CodeIndented" Style="margin-bottom: 0.9em">The exception
Status_Error is propagated if the given file is not open. The exception
Mode_Error is propagated if the mode of the given file is not In_File.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<DIV Class="Examples"><TT><B>procedure</B> Set_Output(File : <B>in</B> File_Type);<BR>
<B>procedure</B> Set_Error (File : <B>in</B> File_Type);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<DIV Class="CodeIndented" Style="margin-bottom: 0.9em">Each operates
on a file of mode Out_File or Append_File. Set_Output sets the current
default output file to File. Set_Error sets the current default error
file to File. The exception Status_Error is propagated if the given file
is not open. The exception Mode_Error is propagated if the mode of the
given file is not Out_File or Append_File.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7</FONT></DIV>
<DIV Class="Examples"><TT><B>function</B> Standard_Input <B>return</B> File_Type;<BR>
<B>function</B> Standard_Input <B>return</B> File_Access;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8</FONT></DIV>
<DIV Class="CodeIndented" Style="margin-bottom: 0.9em">Returns the standard
input file (see <A HREF="AA-A-10.html">A.10</A>), or an access value
designating the standard input file, respectively.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>9</FONT></DIV>
<DIV Class="Examples"><TT><B>function</B> Standard_Output <B>return</B> File_Type;<BR>
<B>function</B> Standard_Output <B>return</B> File_Access;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>10</FONT></DIV>
<DIV Class="CodeIndented" Style="margin-bottom: 0.9em">Returns the standard
output file (see <A HREF="AA-A-10.html">A.10</A>) or an access value
designating the standard output file, respectively.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>11</FONT></DIV>
<DIV Class="Examples"><TT><B>function</B> Standard_Error <B>return</B> File_Type;<BR>
<B>function</B> Standard_Error <B>return</B> File_Access;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>12/1</FONT></DIV>
<DIV Class="CodeIndented">{<I><A HREF="defect1.html#8652/0052">8652/0052</A></I>}
Returns the standard error file (see <A HREF="AA-A-10.html">A.10</A>),
or an access value designating the standard <U>error</U><S>output</S>
file, respectively.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>13</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.9em"> The Form strings
implicitly associated with the opening of Standard_Input, Standard_Output,
and Standard_Error at the start of program execution are implementation
defined. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>14</FONT></DIV>
<DIV Class="Examples"><TT><B>function</B> Current_Input <B>return</B> File_Type;<BR>
<B>function</B> Current_Input <B>return</B> File_Access;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>15</FONT></DIV>
<DIV Class="CodeIndented" Style="margin-bottom: 0.9em">Returns the current
default input file, or an access value designating the current default
input file, respectively.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>16</FONT></DIV>
<DIV Class="Examples"><TT><B>function</B> Current_Output <B>return</B> File_Type;<BR>
<B>function</B> Current_Output <B>return</B> File_Access;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>17</FONT></DIV>
<DIV Class="CodeIndented" Style="margin-bottom: 0.9em">Returns the current
default output file, or an access value designating the current default
output file, respectively.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>18</FONT></DIV>
<DIV Class="Examples"><TT><B>function</B> Current_Error <B>return</B> File_Type;<BR>
<B>function</B> Current_Error <B>return</B> File_Access;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>19</FONT></DIV>
<DIV Class="CodeIndented" Style="margin-bottom: 0.9em">Returns the current
default error file, or an access value designating the current default
error file, respectively.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>20/1</FONT></DIV>
<DIV Class="Examples"><TT>{<I><A HREF="defect1.html#8652/0051">8652/0051</A></I>}
<BR>
<B>procedure</B> Flush (File : <B>in</B> <S><B>out</B> </S>File_Type);<BR>
<B>procedure</B> Flush;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>21</FONT></DIV>
<DIV Class="CodeIndented">The effect of Flush is the same as the corresponding
subprogram in Streams.Stream_IO (see <A HREF="AA-A-12-1.html">A.12.1</A>).
If File is not explicitly specified, Current_Output is used. </DIV>
<H4 ALIGN=CENTER>Erroneous Execution</H4>
<DIV Class="Paranum"><FONT SIZE=-2>22/1</FONT></DIV>
<DIV Class="Normal"> {<I><A HREF="defect1.html#8652/0053">8652/0053</A></I>}
<A NAME="I6145"></A>The execution of a program is erroneous if it <U>invokes
an operation on</U><S>attempts to use</S> a current default input, default
output, or default error file<U>, and if the corresponding file object
is closed or</U><S> that</S> no longer exists. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>22.a.1/1</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Ramification: </B>{<I><A HREF="defect1.html#8652/0053">8652/0053</A></I>}
<U>Closing a default file, then setting the default file to another open
file before accessing it is not erroneous.</U> </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>23/1</FONT></DIV>
<DIV Class="Normal"> <FONT SIZE=-1><I>This paragraph was deleted.</I></FONT>{<I><A HREF="defect1.html#8652/0053">8652/0053</A></I>}
<S>If the Close operation is applied to a file object that is also serving
as the default input, default output, or default error file, then subsequent
operations on such a default file are erroneous.</S> </DIV>
<DIV Class="NotesHeader"><FONT SIZE=-1>NOTES</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>24</FONT></DIV>
<DIV Class="Notes"><FONT SIZE=-1>23 The standard input, standard
output, and standard error files cannot be opened, closed, reset, or
deleted, because the parameter File of the corresponding procedures has
the mode <B>in</B> <B>out</B>.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>25</FONT></DIV>
<DIV Class="Notes"><FONT SIZE=-1>24 The standard input, standard
output, and standard error files are different file objects, but not
necessarily different external files. </FONT></DIV>
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