The Old Turks used the Sogdian script during a certain time. Sogdian script consists of 14 letters (in the last version of 20) and have voiced and voiceless consonants, texts are written from right to left. The writing used by the Sogdians was based on the Old Phoenician, Aramaic and Syrian writings, and was spread on the territory of Sogdiana (now Uzbekistan and Tajikistan, Zeravshan, Kashkadarya).
Brahmi writing contains about 50 generations of signs, is written from left to right, the letters of the alphabet are very similar to Aramaic, Indian inscriptions and are widely used in Southeast Asia. In Southeast Asia, many forms are widespread. The Sogdians along the Silk Road of present Tajikistan and Uzbekistan, the rivers Zeravshan and Kashkadarya were subordinated to the Turkic Kaganate.
In the Old Turkic era there were many monuments and materials in the Sogdian language. The reason was that the Sogdian peasants were settled in the trade centers of Turkey, China, Byzantium. They were followers of Manichaeism and Buddhism and used the Semitic script. Therefore, the first khagan of the Turkic Kaganate established regular political and economic relations with the Sogdians. Thus, along with trade and economic relations between the Turks and Sogdians, Sogdian writing was widely used.
In the Tatpar khagan ritual complex (Taba/Tasbar) (571-582), the Old Sogdian script was used on three sides of the sand stela (29 lines), and on the fourth side – Brahmi script (30 lines). There are 20 texts of the Old Sogdian language on the Little Guest memorial complex of the Niri Khagan era (587-599). In addition to the Niri Khagan era, the Huys Tolgoi Memorial complex has two inscriptions with the Brahmi writing.
On the coins of numismatic complexes found in Shash, Fergana and Bukhara regions of the Tardu khagan period (576-603), the names of the leaders were written with Old Sogdian script. These coins were widely used in trade during the period of the Turgesh Kaganate (699-766). Also the inscriptions on the monument in honor of Ai Tengri Kut Bilge Tengri kagan (808-832) of the Uighur Kaganate period were written in Old Turkic, Sogdian and Chinese languages.