We would obviously need the 26 letters of the English alphabet ("A", "B", "C", etc.) and the 26 lower-case equivalent letters ("a", "b", "c", etc.) requiring 52 characters in our alphabet. But there would also be other characters required for punctuation, such as the full stop (period), comma, and hyphen, and — of course — the "space" character between words. Other characters which might appear in a text document include the dollar sign, the ampersand, and bracket characters. So it appears our alphabet would require in the region of about a hundred characters, or maybe slightly more.
