End Marks are used at the end of sentences or questions. End marks include:
period– A punctuation mark ( . ) indicating a full stop, placed at the end of declarative sentences and other statements thought to be complete, and after many abbreviations.
question mark– a punctuation symbol (?) written at the end of a sentence or phrase to indicate a direct question.
exclamation mark– A punctuation mark (!) used after a sentence that expresses a strong emotion.
End Punctuation:Periods, Question Marks, and Exclamation Points
There are only three ways to end a sentence: with a period (.), a question mark (?), or an exclamation point (!). And because most of us state far more often than we question or exclaim, the period is by far the most popular end mark of punctuation. The American period, by the way, is more commonly known as a full stop in British English. Since around 1600, both terms have been used to describe the mark (or the long pause) at the end of a sentence.
Until the 20th century, the question mark was more commonly known as a point of interrogation–a descendant of the mark used by medieval monks to show voice inflection in church manuscripts. The exclamation point has been used since the 17th century to indicate strong emotion, such as surprise, wonder, disbelief, or pain.
http://www.classzone.com/books/lnetwork_gr12/page_build.cfm?id=quiz&ch=9
http://www.studyzone.org/testprep/ela4/g/exclamationmarksp.cfm
http://www.wwnorton.com/college/english/write/waor/ch31.htm
