How do you distinguish a text file from a binary file? It's just bytes. But for the sake of it, I created a 10 GB .txt file containing the same ASCII-only line

How do you distinguish a text file from a binary file? It's just bytes. But for the sake of it, I created a 10 GB .txt file containing the same ASCII-only line repeated 100 million times. Unsurprisingly, notepad.exe still says the file is too large. And it also hangs with a 1 GB version.