central processing unit vs information processing system

central processing unit and information processing system both are nouns.

Word	Noun	Adjective	Verb	Adverb
central processing unit	Yes	No	No	No
information processing system	Yes	No	No	No

central processing unit (noun)	information processing system (noun)
(computer science) the part of a computer (a microprocessor chip) that does most of the data processing	a machine for performing calculations automatically