1. [n]  an equal exchange; "we had no money so we hd to live by barter"
2. [v]  move (a piece of a program) into memory, in computer science
3. [v]  exchange or give (something) in exchange for

1. \Swap\, v. t. [imp. & p. p. {Swapped}; p. pr. & vb. n.
   {Swapping}.] [OE. swappen to strike; cf. E. to strike a
   bargain; perh. akin to E. sweep. Cf. {Swap} a blow, {Swap},
   v. i.] [Written also {swop}.]
   1. To strike; -- with off. [Obs. or Prov. Eng.] ``Swap off
      his head!'' --Chaucer.
   2. To exchange (usually two things of the same kind); to
      swop. [Colloq.] --Miss Edgeworth.
   

2. \Swap\, v. i. [Cf. {Swap}, v. t.]
   1. To fall or descend; to rush hastily or violently. --C.
      Richardson (Dict.).
            All suddenly she swapt adown to ground. --Chaucer.
   2. To beat the air, or ply the wings, with a sweeping motion
      or noise; to flap.
   

3. \Swap\, n. [Cf. G. schwapp, n., a slap, swap, schwapp,
   schwapps, interj., slap! smack! and E. swap, v.t.]
   1. A blow; a stroke. [Obs. or Prov. Eng.]
   2. An exchange; a barter. [Colloq.] --Sir W. Scott.
   

4. \Swap\, adv. [See {Swap}, n.]
   Hastily. [Prov. Eng.]
   

To move a program from fast-access memory to a slow-access memory ("swap out"), or vice versa ("swap in"). The term often refers specifically to the use of a hard disk (or a swap file) as virtual memory or "swap space".

When a program is to be executed, possibly as determined by a scheduler, it is swapped into core for processing; when it can no longer continue executing for some reason, or the scheduler decides its time slice has expired, it is swapped out again.

This contrasts with "paging" systems in which only parts of a program's memory is transfered.

[Jargon File]