subprogram vs software program

subprogram and software program both are nouns.

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

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

subprogram: 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 subprogram include computer software, package, software, software package, software system.

subprogram (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