The recent advancements in Wireless Sensor Network(WSN)s are the basis for many advanced technologies like lOTs. The constraint-full WSN has the support of operating systems like TinyOS, Contiki, Mantis, SOS, Nanork etc. The most popular and highly documented OS among the many is TinyOS. TinyOS has some limitations in terms of CPU scheduling, realtime applications support, etc. Because of the nonpreemptive First-Come-First-Serve policy of TinyOS the emergency jobs can't get quick responses, and its node throughput decreases. To eradicate this major limitation of TinyOS, many researchers proposed better scheduling mechanisms. In the first fold, this paper aims at briefing-out the main and additional features of TinyOS and in the second fold different scheduling techniques, proposed by different authors are reviewed.