<P> Prior to the advent of Mac OS X (now called macOS), the classic Mac OS system regarded the content of a file (the data fork) to be a text file when its resource fork indicated that the type of the file was "TEXT". Lines of Macintosh text files are terminated with CR characters . </P> <P> Being certified Unix, macOS uses POSIX format for text files . Uniform Type Identifier (UTI) used for text files in macOS is "public. plain - text"; additional, more specific UTIs are: "public. utf8 - plain - text" for utf - 8 - encoded text, "public. utf16 - external - plain - text" and "public. utf16 - plain - text" for utf - 16 - encoded text and "com. apple. traditional - mac - plain - text" for classic Mac OS text files . </P> <P> When opened by a text editor, human - readable content is presented to the user . This often consists of the file's plain text visible to the user . Depending on the application, control codes may be rendered either as literal instructions acted upon by the editor, or as visible escape characters that can be edited as plain text . Though there may be plain text in a text file, control characters within the file (especially the end - of - file character) can render the plain text unseen by a particular method . </P>

The correct way to open the file textfile.txt as readable and editable is