Evolution of early Arabic (9th – 11th century). The Basmala was taken as an example, from kuficQur’an manuscripts. (1) Early 9th century. script with no dots or diacritic marks [1]; (2) and (3)9th – 10th century under Abbasid dynasty, the Abu al-Aswad's system establish red dots with each arrangement or position indicating a different short vowel. Later, a second black dots system was used to differentiate between letters like "fāʼ" and "qāf" [2][3]; (4) 11th century, In Al Farāhídi's system (system we know today) dots were changed into shapes resembling the letters to transcribe the corresponding long vowels [4].
A diacritic[1] is a mark put above, below, through or on a letter. Some examples of diacritics are an acute accent or a grave accent. The word comes from the Greek word διακριτικός (transl. diakritikós, 'distinguishing').
Usually, it affects the way the word is said (pronounced). Most diacritics concern pronunciation because most alphabets do not describe the sounds of words exactly. Diacritics are rare in English, but common in many other languages.