Annotation characters for various programming languages

Comment comparison

There is a wide variety of syntax styles for declaring comments in source code. In italics are used here to BlockComment indicate block comment style. InlineComment In italics are used here to indicate inline comment style.

Language	In-line Comment	Block Comment
Ada, Eiffel, Euphoria, Occam, SPARK, ANSI SQL, ToolBook openscript, and VHDL	-- InlineComment
ALGOL 60		comment BlockComment;
ALGOL 68		¢ BlockComment ¢ comment BlockComment comment co BlockComment co # BlockComment # £ BlockComment £
AppleScript	-- InlineComment	(* BlockComment *)
Assembly language (varies)	; InlineCommentOne example (most assembly languages with line comments only)
AutoHotkey	; InlineComment	/* BlockComment */
AWK, Bash, Bourne shell, C shell, Maple, Python, R, TCL, and Windows PowerShell	# InlineComment	<# BlockComment #>
BASIC (various dialects):	‘InlineComment(Not all dialects) REM InlineComment
C (K&r, ANSI/C89/C90), CHILL, pl/i, and REXX		/* BlockComment */
C (C99), C + +, Go, and JavaScript	// InlineComment	/* BlockComment */
C#	// InlineComment /// InlineComment(XML documentation Comment)	/* BlockComment */ /** BlockComment */(XML documentation Comment)
Cobol	InlineComment(When * was in column 7)
Curl	|| InlineComment	|# BlockComment #| |foo# BlockComment #|
Cobra	# InlineComment	/# BlockComment #/(nestable)
D	// InlineComment /// Documentation InlineComment(Ddoc comments)	/* BlockComment */ /** Documentation BlockComment */(Ddoc comments) /+ BlockComment +/(nestable) /++ Documentation BlockComment +/(Nestable, Ddoc comments)
DCL	$! InlineComment
ECMAScript (JavaScript, ActionScript, etc.)	// InlineComment	/* BlockComment */
Forth	\ InlineComment	( BlockComment )(Single line only) ( before -- after )Stack Comment Convention
FORTRAN 66/77	C InlineComment(The letter ' C ' in the first column makes the entire line a comment).
Fortran 90	! InlineComment(all characters to the line, from the exclamation mark onwards, is comments)
Haskell	-- InlineComment	{- BlockComment -}
Java	// InlineComment	/* BlockComment */ /** BlockComment */(Javadoc documentation Comment)
Lisp and Scheme	; InlineComment	#| BlockComment |#
Lua	-- InlineComment	--[==[ BlockComment]==](variable number of = signs)
Maple	# InlineComment	(* BlockComment *)
Mathematica		% (* BlockComment *)
Matlab	% InlineComment	%{ BlockComment (nestable) %} Note:both Percent–bracket symbols must is the only non-whitespace characters on their respective lines.
Object Pascal (Delphi)	// InlineComment	(* BlockComment *) { BlockComment }
OCaml		(* BlockComment (* nestable *) *)
Pascal, Modula-2, Modula-3, Oberon, and ML:		(* BlockComment *)(OCaml comments is nestable)
Perl and Ruby	# InlineComment	=begin BlockComment =cut(POD documentation Comment) __END__ Comments after end of code
Php	# InlineComment // InlineComment	/* BlockComment */ /** Documentation BlockComment */(PHP Doc comments)
PILOT	R:InlineComment
PL/SQL and TSQL	-- InlineComment	/* BlockComment */
REALbasic	‘ InlineComment // InlineComment rem InlineComment
Sas		* BlockComment; /* BlockComment */
Seed7	# InlineComment	(* BlockComment *)
Simula		comment BlockComment; ! BlockComment;
Smalltalk		"BlockComment"
Smarty		{* BlockComment *}
Standard ML		(* BlockComment *)
TeX, LaTeX, PostScript, Erlang, and S-lang	% InlineComment
Texinfo	@c InlineComment @comment InlineComment
TUTOR	* InlineComment command $$ InlineComment
Visual Basic	‘ InlineComment Rem InlineComment
Visual Basic. NET	‘ InlineComment ‘‘‘ InlineComment(XML documentation Comment) Rem InlineComment
Visual Prolog	% InlineComment	/* BlockComment */

Reference recommendation:

Comparison of programming languages (Syntax) (wiki)

Annotation characters for various programming languages