Emacs is a great editor but it can handle files only as large as 128 MB, at least the 32-bit version. If you decide to use Emacs I recommend to configure it to turn syntax highlighting off for large files. Another way to deal with large files those days was heavy usage of head, tail and split. Atom is a free, open source, hackable programming editor from GitHub for Windows, MacOS, and Linux that integrates with the GitHub app and has thousands of packages and themes available.
Your TextEdit window opens.
The Open dialog appears.
You can also open an existing text file by dragging its icon from the Finder window to the TextEdit icon.
You can also open an existing text file by dragging its icon from the Finder window to the TextEdit icon.
To edit existing text, drag the insertion cursor across the characters to highlight them and type the replacement text. TextEdit automatically replaces the existing characters with those that you type. To simply delete text, highlight the characters and press Delete.
This saves your changes. Alternatively, you can save a new version by choosing File→Save As and typing a new, unique filename.