GNU Emacs Manual. Node: Programs
Chapter 20: Editing Programs
Emacs has many commands designed to understand the syntax of programming
languages such as Lisp and C. These commands can
Move over or kill balanced expressions or sexps (see Lists).
Move over or mark top-level expressions---defuns, in Lisp;
functions, in C (see Defuns).
Show how parentheses balance (see Matching).
Insert, kill or align comments (see Comments).
Follow the usual indentation conventions of the language
(see Program Indent).
The commands for words, sentences and paragraphs are very useful in
editing code even though their canonical application is for editing
human language text. Most symbols contain words (see Words);
sentences can be found in strings and comments (see Sentences).
Paragraphs per se don't exist in code, but the paragraph commands are
useful anyway, because programming language major modes define
paragraphs to begin and end at blank lines (see Paragraphs).
Judicious use of blank lines to make the program clearer will also
provide useful chunks of text for the paragraph commands to work
The selective display feature is useful for looking at the overall
structure of a function (see Selective Display). This feature causes
only the lines that are indented less than a specified amount to appear
on the screen.