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In computer hardware, a word mark or flag is a bit in each memory location on some variable word length computers (e.g., IBM 1401, 1410, 1620) used to mark the end of a word.[1] Sometimes the actual bit used as a word mark on a given machine is not called word mark, but has a different name (e.g., flag on the IBM 1620, because on this machine it is multipurpose).[2]

The term word mark should not be confused with group mark or with record mark, which are distinct characters.


  1. ^ IBM (April 1962). IBM 1401 Data Processing System: Reference Manual (PDF). p. 20. A24-1403-5.
  2. ^