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(emacs)Basic Indent

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Basic Program Indentation Commands
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   The basic indentation commands indent a single line according to the
usual conventions of the language you are editing.

`<TAB>'
     Adjust indentation of current line.

`C-j'
     Equivalent to <RET> followed by <TAB> (`newline-and-indent').

`<LINEFEED>'
     This key, if the keyboard has it, is another way to enter `C-j'.

   The basic indentation command is <TAB>, which gives the current line
the correct indentation as determined from the previous lines.  The
function that <TAB> runs depends on the major mode; it is
`indent-for-tab-command' in Lisp mode, `c-indent-command' in C mode,
etc.  These functions understand the syntax and conventions of
different languages, but they all do conceptually the same job: <TAB>
in any programming-language major mode inserts or deletes whitespace at
the beginning of the current line, independent of where point is in the
line.  If point was inside the whitespace at the beginning of the line,
<TAB> puts it at the end of that whitespace; otherwise, <TAB> keeps
point fixed with respect to the characters around it.

   Use `C-q <TAB>' to insert a tab at point.

   When entering lines of new code, use `C-j' (`newline-and-indent'),
which is equivalent to a <RET> followed by a <TAB>.  `C-j' at the end
of a line creates a blank line and then gives it the appropriate
indentation.

   <TAB> indents lines that start within a parenthetical grouping each
under the preceding line (or the text after the parenthesis).
Therefore, if you manually give one of these lines a nonstandard
indentation, the lines below will tend to follow it.  This behavior is
convenient in cases where you have overridden the standard result of
<TAB> because you find it unaesthetic for a particular line.

   Remember that an open-parenthesis, open-brace or other opening
delimiter at the left margin is assumed by Emacs (including the
indentation routines) to be the start of a function.  Therefore, you
must never have an opening delimiter in column zero that is not the
beginning of a function, not even inside a string.  This restriction is
vital for making the indentation commands fast; you must simply accept
it.  Note: Left Margin Paren, for more information on this.

   Normally, lines are indented with tabs and spaces.  If you want Emacs
to use spaces only, see Note: Just Spaces.