fill-column, an Example Variable
fill-column illustrates a symbol with a value
attached to it: in every GNU Emacs buffer, this symbol is set to some
value, usually 72 or 70, but sometimes to some other value. To find the
value of this symbol, evaluate it by itself. If you are reading this in
Info inside of GNU Emacs, you can do this by putting the cursor after
the symbol and typing C-x C-e:
After I typed C-x C-e, Emacs printed the number 72 in my echo
area. This is the value for which
fill-column is set for me as I
write this. It may be different for you in your Info buffer. Notice
that the value returned as a variable is printed in exactly the same way
as the value returned by a function carrying out its instructions. From
the point of view of the Lisp interpreter, a value returned is a value
returned. What kind of expression it came from ceases to matter once
the value is known.
A symbol can have any value attached to it or, to use the jargon, we can
bind the variable to a value: to a number, such as 72; to a
"such as this"; to a list, such as
oak); we can even bind a variable to a function definition.
A symbol can be bound to a value in several ways. See Setting the Value of a Variable, for information about one way to do this.