subroutine vs software program

subroutine and software program both are nouns.

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

As nouns, software program is a hypernym of subroutine; that is, software program is a word with a broader meaning than subroutine:

subroutine: a set sequence of steps, part of larger computer program
software program: (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

Other hypernyms of subroutine include computer software, package, software, software package, software system.

subroutine (noun)	software program (noun)
a set sequence of steps, part of larger computer program	(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