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A.10.2 Text File Management

Static Semantics

The only allowed file modes for text files are the modes In_File, Out_File, and Append_File. The subprograms given in subclause A.8.2 for the control of external files, and the function End_Of_File given in subclause A.8.3 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: 
Reason: 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.
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. 
Reason: The behavior of Reset should be similar to closing a file and reopening it with the given mode
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. 
23  An implementation can define the Form parameter of Create and Open to control effects including the following: 

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