To minimise development costs and enhance
dependability, modern embedded system development is
increasingly emphasising on software modularity and reuse.
Microcontrollers are extensively employed in embedded
applications that have a very specific and specialised job to
complete. The embedded applications are always resource
constraint which requires efficient utilization of available
resources. A Real Time Operating System (RTOS) is frequently
used in this context to plan task execution as well as enable
intertask communication and synchronisation. This paper
provides the survey of different RTOS available in market and
their applications. Several open source RTOS such as Free RTOS,
VxWorks, SmallRTOS and TinyOS are compared with respect to
the scheduling algorithms used.