The basic structure of the
beginning-of-buffer function has
already been discussed. (See A
This section describes the complex part of the definition.
As previously described, when invoked without an argument,
beginning-of-buffer moves the cursor to the beginning of the
buffer (in truth, the beginning of the accessible portion of the
buffer), leaving the mark at the previous position. However, when the
command is invoked with a number between one and ten, the function
considers that number to be a fraction of the length of the buffer,
measured in tenths, and Emacs moves the cursor that fraction of the
way from the beginning of the buffer. Thus, you can either call this
function with the key command M-<, which will move the cursor to
the beginning of the buffer, or with a key command such as C-u 7
M-< which will move the cursor to a point 70% of the way through the
buffer. If a number bigger than ten is used for the argument, it
moves to the end of the buffer.
beginning-of-buffer function can be called with or without an
argument. The use of the argument is optional.