Most languages use a small number of generic types of languages. Multiple values may be specified, as many languages use both single and double quotes. Both paired and line comments can be specified, as can multiple occurrences of each. They have an opening string and a closing string. This defines the string that closes a paired comment.
Some languages allow paired comments to be nested.
This specifies the string that is considered to be a language keyword. Normally this is used for those functions that are builtin into the language, but can be any identifier. Headers are lines within a file that begin with a particular string and usually identify different parts of the file. They are similar to labels. Labels are lines within a file that end with a particular string.