Upvote:8
According to this article, Pope Sylvester II (Gerbert d'Aurillac, c943-1003), is credited with re-introducing the abacus into Europe without an explicit use of the number zero. This was because it had not been introduced in the European mathematical vocabulary (Fibonacci did this around 1202, and it took centuries for it to become established), rather than an explicit decree that it should be banned.
A detailed description of how Gerbert's abacus worked can be found here.
It's also interesting to note that Gottfried Leibniz had a somewhat mystical interpretation of the binary numbers, with one representing God and zero the void.