TextEdit can and has always been able to read/write text files.
You simply need to change its default format from RTF to TXT. It's a simple click of the "Plain text" radio button in the
TextEdit->
Preferences,
New Document:
Format section. Second, check the 'Add ".txt" extension to plain text files' in the
TextEdit->
Preferences->
Open and Save section. By the way, I suggest changing, the
Finder->
Preferences->Advanced, to "Show all filename extensions".
TextEdit can be used to read/write plain text, HTML, XML, Basic, Pascal, PHP, C++, .plist, etc., etc. You just need to Save as ".txt" and then change those 3 letters to whatever the other language needs. Of course, you won't have the color coding that
BBEdit or a compiler would provide but all those languages are simply text files until a compiler/interpreter is needed.
BBEdit is great, I've used it for decades, but one should open, inspect and know what any app's Prefs can do for you. Especially those apps that
Apple gives you. Just because
Apple thinks we should do things their way does not mean we actually have to.
I used
Filemaker on the 128K Mac(!), as a page layout app before
Pages was ever a gleam in Steve Job's eye!