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(vip)Basic Concepts

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Basic Concepts
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   We begin by explaining some basic concepts of Emacs.  These concepts
are explained in more detail in the GNU Emacs Manual.

   Conceptually, a "buffer" is just a string of ASCII characters and two
special characters <PNT> ("point") and <MRK> ("mark") such that the
character <PNT> occurs exactly once and <MRK> occurs at most once.  The
"text" of a buffer is obtained by deleting the occurrences of <PNT> and
<MRK>.  If, in a buffer, there is a character following <PNT> then we
say that point is "looking at" the character; otherwise we say that
point is "at the end of buffer".  <PNT> and <MRK> are used to indicate
positions in a buffer and they are not part of the text of the buffer.
If a buffer contains a <MRK> then the text between <MRK> and <PNT> is
called the "region" of the buffer.

   Emacs provides (multiple) "windows" on the screen, and you can see
the content of a buffer through the window associated with the buffer.
The cursor of the screen is always positioned on the character after
<PNT>.

   A "keymap" is a table that records the bindings between characters
and command functions.  There is the "global keymap" common to all the
buffers.  Each buffer has its "local keymap" that determines the "mode"
of the buffer.  Local keymap overrides global keymap, so that if a
function is bound to some key in the local keymap then that function
will be executed when you type the key.  If no function is bound to a
key in the local map, however, the function bound to the key in the
global map becomes in effect.