Variable: major-mode
major-mode is a customizable and buffer-local variable defined in
buffer.c.
Documentation
Symbol for current buffer's major mode.
The default value (normally fundamental-mode) affects new buffers.
A value of nil means to use the current buffer's major mode, provided
it is not marked as "special".
Probably introduced at or before Emacs version 29.1.
Source Code
// Defined in /usr/src/emacs/src/buffer.c
DEFVAR_PER_BUFFER ("major-mode", &BVAR (current_buffer, major_mode),
Qsymbolp,
doc: /* Symbol for current buffer's major mode.
The default value (normally `fundamental-mode') affects new buffers.
A value of nil means to use the current buffer's major mode, provided
it is not marked as "special". */);