1. \While\, n. [AS. hw[=i]l; akin to OS. hw[=i]l, hw[=i]la,
   OFries. hw[=i]le, D. wigl, G. weile, OHG. w[=i]la, hw[=i]la,
   hw[=i]l, Icel. hv[=i]la a bed, hv[=i]ld rest, Sw. hvila, Dan.
   hvile, Goth. hweila a time, and probably to L. quietus quiet,
   and perhaps to Gr. ? the proper time of season. [root]20. Cf.
   {Quiet}, {Whilom}.]
   1. Space of time, or continued duration, esp. when short; a
      time; as, one while we thought him innocent. ``All this
      while.'' --Shak.
            This mighty queen may no while endure. --Chaucer.
            [Some guest that] hath outside his welcome while,
            And tells the jest without the smile. --Coleridge.
            I will go forth and breathe the air a while.
                                                  --Longfellow.
   2. That which requires time; labor; pains. [Obs.]
            Satan . . . cast him how he might quite her while.
                                                  --Chaucer.
   {At whiles}, at times; at intervals.
            And so on us at whiles it falls, to claim Powers
            that we dread.                        --J. H.
                                                  Newman.
   {The while}, {The whiles}, in or during the time that;
      meantime; while. --Tennyson.
   {Within a while}, in a short time; soon.
   {Worth while}, worth the time which it requires; worth the
      time and pains; hence, worth the expense; as, it is not
      always worth while for a man to prosecute for small debts.
   

2. \While\, v. t. [imp. & p. p. {Whiled}; p. pr. & vb. n.
   {Whiling}.]
   To cause to pass away pleasantly or without irksomeness or
   disgust; to spend or pass; -- usually followed by away.
         The lovely lady whiled the hours away.   --Longfellow.
   

3. \While\, v. i.
   To loiter. [R.] --Spectator.
   

4. \While\, conj.
   1. During the time that; as long as; whilst; at the same time
      that; as, while I write, you sleep. ``While I have time
      and space.'' --Chaucer.
            Use your memory; you will sensibly experience a
            gradual improvement, while you take care not to
            overload it.                          --I. Watts.
   2. Hence, under which circumstances; in which case; though;
      whereas.
   {While as}, {While that}, during or at the time that. [Obs.]
   

5. \While\, prep.
   Until; till. [Obs. or Prov. Eng. & Scot.]
         I may be conveyed into your chamber; I'll lie under
         your bed while midnight.                 --Beau. & Fl.
   

The loop construct found in nearly all imperative programming languages which executes one or more instructions (the "loop body") repeatedly so long as some condition evaluates to true. In contrast to a repeat loop, the loop body will not be executed at all if the condition is false on entry to the while.

For example, in C, a while loop is written

        while (<expr>) <statement>;

where is any expression and is any statement, including a compound statement within braces

"..".