File Types  89  Write (F, E1, ... , En)  is equivalent to the statement  begin Write(F,E1); ... ;Write(F,En)  end  The advantage of using these procedures lies not only in brevity, but  also in conceptual simplicity, since the existence of a buffer variable  Fi,  which is sometimes undefined, may be ignored. The buffer variable  may, however, be useful as a "lookahead" device.  Examples of declarations  Examples of statements with files  Files may be local to a program (or local to a procedure), or they  may already exist outside the program. The latter are called  external  files.  External files are passed as parameters in the program heading  (see Chapter 3) into the program.  The next two programs illustrate the use of files. Program 9.1  reprocesses a file of real numbers representing measurements produced  by an instrument or another program. Program 9.2 operates on two files  A  := Datai;  Get (Data)  Read(Data,A)  Plotfilei.c  := Red;  Plotfilei.Len  := 17;  Put (Plotfile)  Clubi:= P;  Put (C1ub)  Write(Club,P)  var Data:  file of Integer;  A:  Integer;  var Plotfile:  file of  record  C:  Color;  Len:  Natural  end;  var Club:  file of Person;  P:  Person; 