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  Arguments
 
    file_variable    Unopened typed, untyped, or text file
 
    filename         String expression representing an external file
                     name, device name, or null string; maximum 79
                     characters
 
  Description
 
    The Assign procedure associates a file variable with an external
    file name. After a successful assignment, all operations directed
    to file_variable act on the external file represented by filename.
    The file_variable remains associated with filename until Assign is
    called for file_variable again with another filename argument.
 
    The filename argument can be one of the following:
 
      1. A simple file name or a full DOS path name of the form
         drive:path\file.ext where
 
             drive is a disk-drive identifier ( A..Z │ a..z ). If not
             designated, the current drive is assumed.
 
             path is zero or more directory names, each separated by a
             backslash (\). Shorthand directory notation '.' and '..'
             may be used. A path starting with a backslash begins at
             the root; otherwise, it begins from the current directory.
             If not designated, DOS assumes the current directory for
             file.ext.
 
             file.ext is a DOS name for an external file of any type and
             includes both the base name and the file extension.
 
      2. A hardware device such as one of the following:
 
      Filename                  Standard Device               I or O
      ══════════════════════    ═════════════════════════     ══════
 
      'AUX'                     Auxiliary (COM1 synonym)      I/O
      'COM1', 'COM2', 'COM3'    Communication ports 1-3       I/O
      'CON'                     Console with keyboard         I/O
      'LPT1', 'LPT2', 'LPT3'    Printer ports 1-3             O only
      'NUL'                     Null device ("bit bucket")    I/O
      'PRN'                     Printer (LPT1 synonym)        O only
 
      3. A null (empty) string, given as ''. To be able to specify
         file_variable when doing standard I/O, Assign file_variable to
         a null string, then Reset or Rewrite file_variable. Standard
         I/O involves the standard files Input and Output and is usually
         directed to the keyboard and screen. Either can be redirected
         to a file by using the DOS operators for input redirection
         (<), and output redirection (>). This redirection ability
         depends on whether the Crt unit is used.
 
         When the Crt unit is not used, the redirection operators
         associate standard I/O with files specified on the DOS command
         line when the program is run. If Read and Write are called
         with no file specified or if file_variable (assigned to a null
         string) is specified, I/O is performed on the redirected
         files.
 
         When the Crt unit is used, the unit assigns I/O to the Crt and
         overrides I/O redirection. Redirection is reenabled in two
         ways:
 
             To Read and Write through file_variable, Assign
             file_variable to a null string and then Reset or Rewrite
             file_variable. Specify file_variable when doing I/O on the
             redirected file.
 
             To Read or Write through the standard text files Input or
             Output, Assign the name Input or Output to a null string,
             call Reset or Rewrite, and do I/O on the redirected file
             without specifying a file name. If this second method is
             used, I/O to the console is unavailable unless the
             AssignCrt procedure is used.
 
    If no external file exists by the name filename, the call succeeds.
    A subsequent call to Rewrite creates a file. A call to Append or
    Reset will fail with an I/O error.
 
    If Assign is passed a file_variable already associated with an open
    file, the previous file assignment is lost.
 
    If Assign is passed a filename that is the name of an open file,
    no error occurs, but later behavior may be unpredictable.