computer vs computing device

computer and computing device both are nouns.

Word	Noun	Adjective	Verb	Adverb
computer	Yes	No	No	No
computing device	Yes	No	No	No

As nouns, computer and computing device are synonyms defined as:

computer and computing device: a machine for performing calculations automatically

computer (noun)	computing device (noun)
a machine for performing calculations automatically	a machine for performing calculations automatically
an expert at calculation (or at operating calculating machines)