C-ben a tolower függvénynek ha kisbetűket adok és '0', '1' etc. -t akkor azokkat mit csinál?

Google-be beírod hogy "tolower c", az első 10 találat biztos hogy leírja, csak el kéne olvasni. Beidézek párat:

int tolower ( int c );

"This function returns lowercase equivalent to c, if such value exists, else c remains unchanged. The value is returned as an int value that can be implicitly casted to char."

"Return value:

The lowercase equivalent to c, if such value exists, or c (unchanged) otherwise.

The value is returned as an int value that can be implicitly casted to char."

"Converts c to its lowercase equivalent if c is an uppercase letter and has a lowercase equivalent. If no such conversion is possible, the value returned is c unchanged.

Notice that what is considered a letter may depend on the locale being used; In the default "C" locale, an uppercase letter is any of: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z, which translate respectively to: a b c d e f g h i j k l m n o p q r s t u v w x y z.

In other locales, if an uppercase character has more than one correspondent lowercase character, this function always returns the same character for the same value of c.

In C++, a locale-specific template version of this function (tolower) exists in header <locale>."

etc.