Which scripts are used to write Khalkha, Buryat, Kalmyk, and Oirat?

The writing systems used for these Mongolian languages are as follows:

• Khalkha: Primarily written using the Cyrillic script, which is the standard for the modern language in Mongolia.1
• Buryat: Written using the Cyrillic script.1
• Kalmyk: Written using the Cyrillic script.1
• Oirat: Utilizes a variant of the traditional Mongolian vertical script.1

While the traditional Mongolian script—which is of Syriac derivation—has historically served as the literary standard for various Mongolian languages, modern usage varies significantly by region and political context.21