Variable: default-directory
default-directory is a buffer-local variable defined in buffer.c.
Documentation
Name of default directory of current buffer.
It should be an absolute directory name; on GNU and Unix systems,
these names start with "/" or "~" and end with "/".
To interactively change the default directory, use the command cd.
Probably introduced at or before Emacs version 1.11.
Source Code
// Defined in /usr/src/emacs/src/buffer.c
DEFVAR_PER_BUFFER ("default-directory", &BVAR (current_buffer, directory),
Qstringp,
doc: /* Name of default directory of current buffer.
It should be an absolute directory name; on GNU and Unix systems,
these names start with "/" or "~" and end with "/".
To interactively change the default directory, use the command `cd'. */);