Viharas were for the purpose of living, Chaityas were assemblies for the purpose of discussions. Further, Chaityas were with Stupas, Viharas did not have stupas.
Sakatayana was a Jain writer of the 9th century A.D.He lived during the reign of Rashtrakuta ruler Amoghavarsha. He was the founder of a new school. His main work was Sabdansusana.