Editing Worst-case execution time (section)

== What it is used for ==

Worst case execution time is typically used in reliable [[real-time systems]], where understanding the worst case timing behaviour of software is important for reliability or correct functional behaviour. 

As an example, a computer system that controls the behaviour of an engine in a vehicle might need to respond to inputs within a specific amount of time. One component that makes up the response time is the time spent executing the software – hence if the software worst case execution time can be determined, then the designer of the system can use this with other techniques such as [[Scheduling analysis real-time systems|schedulability analysis]] to ensure that the system responds fast enough.

While WCET is potentially applicable to many real-time systems, in practice an assurance of WCET is mainly used by real-time systems that are related to high reliability or safety. For example, in airborne software some attention to software is required by [[DO178C]] section 6.3.4. The increasing use of software in automotive systems is also driving the need to use WCET analysis of software.

In the design of some systems, WCET is often used as an input to [[Scheduling analysis real-time systems|schedulability analysis]], although a much more common use of WCET in critical systems is to ensure that the pre-allocated timing budgets in a partition-scheduled system such as [[ARINC 653]] are not violated.