The Free On-line Dictionary of Computing (30 December 2018):

modulo operator

    (mod) The operator that returns the remainder
   after integer division of its first argument by its second.
   Written as "%" in C and some other languages.

   Where the second argument is a power of two, the result can be
   calculated much more quickly using bitwise and with the
   appropriate bit-mask.

   (1999-07-12)