text file vs writing system

text file

noun
  • A data file in a character encoding that allows it to be read in non-specialised text editor. 

  • A data file containing only plain, human-readable text, distinct from documents with embedded formatting 

writing system

noun
  • The basic type of a system for writing languages. For example, alphabetic writing or logographic writing. 

  • A system for writing one or more languages; a particular alphabetic, syllabic, logographic, or other scheme. For example, the Latin alphabet or the Cyrillic alphabet. 

How often have the words text file and writing system occurred in a corpus of books? (source: Google Ngram Viewer )