All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
The Ottoman Style Arabic Script writes some words with واو"" (و)instead of ألف (ا) contrary to the Arabic language dictation script, and these words are eight words which are as follows:
الصلاة ، الحياة ، الربا ، مشكاة ، الزكاة ، النجاة ، مناة ، الغداة
As regards whether or not the واو is written as a rule so that the ألف (ا) will be written on it, then the answer is no because the Companions did not write a small ألف (ا) on the واو but it was the scholars of Arabic language dictation who wrote it to make its recitation easier for the public as they wrote the vowels and dots and the words الصلاة and الزكاة with واو to indicate that the ألف (ا) was changed from a واو as stated by the scholars of the Arabic language dictation.
Az-Zarqaani wrote in his book Manaahil Al-‘Irfaan, “To indicate the origin of the letter like الصلاة and الزكاة as they were written like this الصلوة and الزكوة to understand that the ألف (ا) in these words is changed to واو without dots or vowels. ...”
Allaah Knows best.