Writing-system as a concept in linguistics

In a proposed systemisation of terminology concerned with writing, the most precise relationship assigned is that between 'writing-system ' as genus and 'orthography ' as one of its species, viz. the species designed to serve the general purposes of literacy, as opposed to the specialised purposes of the other four species of writing-system (stenography, cryptography, paedography, technography). 'Orthography' is further distinguished from 'spelling*, spelling being that part of a writing-system which realises the verbal component of writing. A non-verbal component of writing is recognised analogous to the non-verbal component of speech, and a linguistic 'graphology ' is called for, comparable to phonology.