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An alphabet usually has a conventional order of letters. Alphabetical order of words and phrases is based on this order in combination with the principle of lexicographical order.
A blank space is treated as a character that comes before the letters.
Conventions may vary where to position digits and special characters.
A common order is:
A more advanced system may consider numbers as such instead of just considering the digits; in that case 100 does not come between 10 and 11, but after 11. This can be extended to Roman numerals.
However, if a number is spelled out it is treated as a word.
For example:
Normally capitals and lowercase letters have the same position. On computer systems sometimes a crude system is used, e.g. based on ASCII order. In that case "a" comes after "Z", see e.g. .
The Alphabetical order varies with the language involved. Languages other than English do have different criteria on what word comes before or after another.