Post History

https://theasciicode.com.ar/extended-ascii-code/majuscule-c-cedilla-uppercase-ascii-code-128.html

Octal 101 is 65, which is ASCII/UTF-8 for A - a valid character.

Octal 200 is 128, which is ASCII/UTF-8 or whatever for Ç - which is also a valid character.

> A file that contains characters organized into zero or more lines. 

Lines are newline characters, which are octal 012.  The above rule means newlines can appear, but don't have to.

Really, as long as the file contains no zero bytes (which are NUL), it's a text file.