Most contemporary linguists work under the assumption that spoken (or signed) language is more fundamental than written language. This is because:

• Speech appears to be universal to all human beings capable of producing and hearing it, while there have been many cultures and speech communities that lack written communication
• Speech evolved before human beings invented writing
• People learn to speak and process spoken languages more easily and much earlier than writing.

Nonetheless, linguists agree that the study of written language can be worthwhile and valuable. For research that relies on corpus linguistics and computational linguistics, written language is often much more convenient for processing large amounts of linguistic data. Large corpora of spoken language are difficult to create and hard to find, and are typically transcribed and written. In addition, linguists have turned to text-based discourse occurring in various formats of computer-mediated communication as a viable site for linguistic inquiry.
The study of writing systems themselves is, in any case, considered a branch of linguistics.