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What is a Real-Time Operating System (RTOS)?
In general, an operating system (OS) is responsible for
managing the hardware resources of a computer and hosting
applications that run on the computer. An RTOS performs
these tasks, but is also specially designed to run applications
with very precise timing and a high degree of reliability. This
can be especially important in measurement and automation
systems where downtime is costly or a program delay could
cause a safety hazard.
To be considered “real-time”, an operating system
must have a known maximum time for each of the critical
operations that it performs (or at least be able to guarantee
that maximum most of the time). Some of these operations
include OS calls and interrupt handling. Operating systems
that can absolutely guarantee a maximum time for these
operations are commonly referred to as “hard real-time”, while
operating systems that can only guarantee a maximum most
of the time are referred to as “soft real-time”.
(Extraído e adaptado de: http://www.ni.com/white-paper/3938/en/)