atomic: adj. [from Gk. atomos, indivisible]
1. Indivisible; cannot be split up. For example, an instruction may
be said to do several things ‘atomically’, i.e., all the things
are done immediately, and there is no chance of the instruction being
half-completed or of another being interspersed. Used esp. to convey that
an operation cannot be screwed up by interrupts. “This routine locks
the file and increments the file's semaphore atomically.”
2. [primarily techspeak] Guaranteed to complete successfully or not
at all, usu. refers to database transactions. If an error prevents a
partially-performed transaction from proceeding to completion, it must be
“backed out”, as the database must not be left in an
inconsistent state.
Computer usage, in either of the above senses, has none of the
connotations that ‘atomic’ has in mainstream English (i.e. of
particles of matter, nuclear explosions etc.).