Al-Farahidi is also credited with the current standard for Arabic diacritics; rather than a series of indistinguishable dots, it was al-Farahidi who introduced different shapes for the vowel diacritics in Arabic, which simplified the writing system so much that it has not been changed since.[41] He also began using a small letter shin to signify the shadda mark for doubling consonants. Al-Farahidi's style for writing the Arabic alphabet was much less ambiguous than the previous system where dots had to perform various functions, and while he only intended its use for poetry it was eventually used for the Qur'an as well.[42]