+The variable @code{calc-embedded-open-close-plain-alist} is used to
+set @code{calc-embedded-open-plain} and
+@code{calc-embedded-close-plain} to different strings
+depending on the major mode of the editing buffer.
+It consists of a list of lists of the form
+@code{(@var{MAJOR-MODE} @var{OPEN-PLAIN-STRING}
+@var{CLOSE-PLAIN-STRING})}, and its default value is
+@example
+ ((c++-mode "// %% " " %%\n")
+ (c-mode "/* %% " " %% */\n")
+ (f90-mode "! %% " " %%\n")
+ (fortran-mode "C %% " " %%\n")
+ (html-helper-mode "<!-- %% " " %% -->\n")
+ (html-mode "<!-- %% " " %% -->\n")
+ (nroff-mode "\\\" %% " " %%\n")
+ (pascal-mode "@{%% " " %%@}\n")
+ (sgml-mode "<!-- %% " " %% -->\n")
+ (xml-mode "<!-- %% " " %% -->\n")
+ (texinfo-mode "@@c %% " " %%\n"))
+@end example
+Any major modes added to @code{calc-embedded-open-close-plain-alist}
+should also be added to @code{calc-embedded-announce-formula-alist}
+and @code{calc-embedded-open-close-mode-alist}.
+@end defvar