Nouns of plural form preceding another noun

I was reading Computers, Communications, and Information A User's Introduction (Seventh Edition) by Sarah E. Hutchinson and Stacey C. Sawyer.

The authors consistently used such terms as communications hardware and applications software. I thought we should use communication hardware and application software instead. Why did the authors use nouns of plural form this way?

EDIT: As far as I can remember from English grammar courses, a noun should typically be modified by a single noun preceding it. Rarely have I seen such usages as in the book.

Solution 1:

I do believe that in both phrases you mention are grammatical and colloquially interchangeable.

However, I also think that there is actually a difference in the meaning. Peter Shor suggests this in his comment also. "Communications" and "Applications" refer to fields, or topic areas. So while "communication software" means something like "software that allows people to communicate with each other", "communications software" might mean something more like "software used in or made for the communications field". It's actually useful to use the plural here to disambiguate these two meanings. Notice that "Communications" is also plural in the title of the book - it's the name of a field or topic area.

Solution 2:

Why did the authors use nouns of plural form this way?

The real answer can only be found by asking them or their editor...

As someone who works in that domain I don't make any real difference between the plural or singular adjective in these cases; I prefer the singular as you do.

A couple of things to give some perspective:

1. Technical communications are hardly a source of grammatical correctness. If there is a real distinction between plural or singular in the cases you cited, it's not used with consistency in the field (although as you point out, the authors are consistent in their book).
2. Google (with quotes) "communications hardware" and you'll find 269,000 hits.
3. Google (with quotes) "communication hardware" and you'll find 276,000 hits.
4. Google (with quotes) "applications software" and you'll find 6,440,000 hits.
5. Google (with quotes) "application software" and you'll find 13,500,000 hits.