software vs subroutine

software and subroutine both are nouns.

Word	Noun	Adjective	Verb	Adverb
software	Yes	No	No	No
subroutine	Yes	No	No	No

As nouns, subroutine is a hyponym of software; that is, subroutine is a word with a more specific, narrower meaning than software:

software: (computer science) written programs or procedures or rules and associated documentation pertaining to the operation of a computer system and that are stored in read/write memory
subroutine: a set sequence of steps, part of larger computer program

software (noun)	subroutine (noun)
(computer science) written programs or procedures or rules and associated documentation pertaining to the operation of a computer system and that are stored in read/write memory	a set sequence of steps, part of larger computer program