The Collaborative International Dictionary of English v.0.48:

File \File\ (f[imac]l), n. [F. file row (cf. Pr., Sp., Pg., &
   It. fila), LL. fila, fr. L. filum a thread. Cf. Enfilade,
   Filament, Fillet.]
   1. An orderly succession; a line; a row; as:
      (a)
      (Mil.) A row of soldiers ranged one behind another; -- in
             contradistinction to rank, which designates a row
             of soldiers standing abreast; a number consisting
             the depth of a body of troops, which, in the
             ordinary modern formation, consists of two men, the
             battalion standing two deep, or in two ranks.
             [1913 Webster]

   Note: The number of files in a company describes its width,
         as the number of ranks does its depth; thus, 100 men in
         "fours deep" would be spoken of as 25 files in 4 ranks.
         --Farrow.
      (b) An orderly collection of papers, arranged in sequence
          or classified for preservation and reference; as,
          files of letters or of newspapers; this mail brings
          English files to the 15th instant.
      (c) The line, wire, or other contrivance, by which papers
          are put and kept in order.
          [1913 Webster]

                It is upon a file with the duke's other letters.
                                                  --Shak.
      (d) A roll or list. "A file of all the gentry." --Shak.

   2. Course of thought; thread of narration. [Obs.]
      [1913 Webster]

            Let me resume the file of my narration. --Sir H.
                                                  Wotton.
      [1913 Webster]

   3. (computers) a collection of data on a digital recording
      medium treated as a unit for the purpose of recording,
      reading, storage, or indexing; -- such a file is typically
      accessible by computer programs by the use of a file name.
      The data may be of any type codable digitally, such as
      simple ASCII-coded text, complex binary-coded data, or an
      executable program, or may be itself a collection of other
      files.
      [PJC]

   File firing, the act of firing by file, or each file
      independently of others.

   File leader, the soldier at the front of any file, who
      covers and leads those in rear of him.

   File marching, the marching of a line two deep, when faced
      to the right or left, so that the front and rear rank
      march side by side. --Brande & C.

   Indian file, or Single file, a line of people marching
      one behind another; a single row. Also used adverbially;
      as, to march Indian file.

   On file, preserved in an orderly collection; recorded in
      some database.

   Rank and file.
      (a) The body of soldiers constituting the mass of an army,
          including corporals and privates. --Wilhelm.
      (b) Those who constitute the bulk or working members of a
          party, society, etc., in distinction from the leaders.
          [1913 Webster]