tablet vs computing machine

tablet and computing machine both are nouns.

Word	Noun	Adjective	Verb	Adverb
tablet	Yes	No	No	No
computing machine	Yes	No	No	No

As nouns, computing machine is a hypernym of tablet; that is, computing machine is a word with a broader meaning than tablet:

tablet (noun)	computing machine (noun)
a dose of medicine in the form of a small pellet	a machine for performing calculations automatically
a small flat compressed cake of some substance
a slab of stone or wood suitable for bearing an inscription
a portable computer with a touchscreen
a number of sheets of paper fastened together along one edge