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A.10.2 Text File Management

Static Semantics

1
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: 
2
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. 
3
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.
4
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. 
5
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. 
NOTES
6
27  An implementation can define the Form parameter of Create and Open to control effects including the following: 
7
the interpretation of line and column numbers for an interactive file, and
8
the interpretation of text formats in a file created by a foreign program. 

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