reckoner vs computer

reckoner and computer both are nouns.

Word	Noun	Adjective	Verb	Adverb
reckoner	Yes	No	No	No
computer	Yes	No	No	No

As nouns, reckoner and computer are synonyms defined as:

reckoner and computer: an expert at calculation (or at operating calculating machines)

Other synonyms of reckoner include calculator, estimator, figurer.

reckoner (noun)	computer (noun)
a handbook of tables used to facilitate computation	a machine for performing calculations automatically
an expert at calculation (or at operating calculating machines)	an expert at calculation (or at operating calculating machines)