plain text vs text file

plain text

noun
  • Data which consists only of human-readable text, as opposed to machine-readable binary data or formatting markup. 

  • Text or any data that is to be encrypted (as opposed to ciphertext). 

adj
  • Consisting only of plain text. 

text file

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

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

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