Periodization of Islamic script's history on the basis of first hand sources

Periodization is the process of dividing the time into smaller blocks so that, each block has its uniformity.
Almost all of the historians have narrated the history of Islamic calligraphy on the basis of political periods or chronometric dating. But, in spite of the advantages, these methods are not consistence with the real evolution of calligraphy. So, the method of periodization is better to be firstly consistence with the visual evolution of calligraphy and secondly, on the basis of local principles. To this, in this article the historical reports of calligraphy recorded in old manuals, prefaces of albums (Moraq`s), and biographies (Tazkares) in a descriptive- analytics methos were studied and one of the periodization methods used for classification of scripts` history explained. To do this the following questions are answered: which kind of periosdization was used more in the first hand resources? What are the charactristics of every period? What are advantages and disadvantages of this periodization model? The basis of the method is the alterations done by outstanding calligraphers in the styles of their time. Firstly, in this method the section of periods is the time of calligraphers whose styles became the norm of their time. Secondly, the method is of the methods based on the period style. Thirdly, the method can be used for classification of all the Islamic scripts. But the significant point is that in historiography by the method, the norm of periods is the basis of historical narration so the historians should pay enough attention to the trivial styles.