Let me clear up a common misconception. When most people say writing in code, what they really mean is writing using a cipher. A code is when a symbol, word, or phrase is used to stand for a different word, phrase, or sentence. A cipher is were each letter in a word is represented with a different letter or symbol.
The dash is a punctuation mark that is similar to a hyphen or minus sign, but differs from both of these symbols primarily in length and function.
The dash that is usually typed as two hyphens (--) is typeset as an em dash (-). It indicates a break in thought and can be used within a sentence to insert a parenthetical phrase. Neither a double hyphen nor an em dash should have spaces on either side. The en dash (-) is used between ranges of numbers or dates, or between adjectival phrases containing two-word concepts (1984-87; pp.