92  Pascal User Manual  9.B.  Textfiles  Textfiles  are  files  that consist of  a sequence of characters that is  subdivided into variable-length  tOICS.  The predefined type Text  is  used to declare textfiles.  We may consider the type Text as being defined over the base type  Char  extended by a (hypothetical) line terminator or end-of-line  marker. Therefore type Text  is  nut  equivalent to (Packed) file  of  Char. This end-of-line marker can be both recognized and generated  by the following special textfile procedures.  If  F  is a textfile and Ch a character variable,  Input  and Output  are the names of two standard textfile variables  used as program parameters for le;!ible reading and writing of text.  Chapter 12 describes them in detail t, 'gether with extended forms ofthe  procedures P.ead, Write, Readln, ani  ',~citeln.  The following program schem; ta  use  the above conventions to  demonstrate some typical operation. performed on textfiles.  1.  Writing a textfile  Y.  Assume that  (")  computes a (next) character  and assigns it to parameter c.  If  the .:lIlTcnt line is to be terminated, a  Boolean variable  Bl is set to true; and if the text is to be terminated, B2  is set to true.  Writeln  (F)  terminates the current line of the textfile F.  Readln  (F)  skips to the beginning of the next line of the textfile  F  (Fi becomes the fiN character of the next line).  Eoln  (F)  a Boolean function mdicating whether the end of the  current line in the te '(tfile  F  has been reached.  (If  true,  Fi corresponds to the position of a line separator, but Fi  is a  blank.)  Write (F,  Ch)  is an abbreviation for  begin Fi :  =  Ch;  E  .. t  (F)  end  Read (F, Ch)  assigns the character iat the current position of file F  or the value of Fi to Ch, followed by a Get  (F) .  The  choice is implement;ltion-dependent. 