code flag vs signal flag

code flag and signal flag both are nouns.

Word	Noun	Adjective	Verb	Adverb
code flag	Yes	No	No	No
signal flag	Yes	No	No	No

As nouns, signal flag is a hypernym of code flag; that is, signal flag is a word with a broader meaning than code flag:

Other hypernyms of code flag include flag.

code flag (noun)	signal flag (noun)
one of an international code of flag signals used between ships	a rectangular piece of fabric used as a signalling device