The following table shows the components and features of Keil RTX5 RTOS.

Migration paths	Keil RTX5 supports the CMSIS-RTOS v2 API. Compatibility layer provides CMSIS-RTOS v1 API compliance. API layers can be intermixed in the same project. Other operating systems that support CMSIS-RTOS v2 API: FreeRTOS Zephyr
FuSa RTX RTOS	The use of a real-time operating system (RTOS) in a safety-critical system demands that the RTOS component also undergoes rigorous verification. When regulatory certification is mandatory, specific documentation and testing processes for the targeted safety standards are required: Arm provides FuSa RTX RTOS as part of the Functional Safety Run-Time System (FuSa RTS) package. FuSa RTX RTOS: Enables and streamline the product safety certification. Qualifies for use in automotive, industrial, railway, and medical applications.
Strictly validated code	MISRA C rules: RTX is written in C using C99 language extensions with MISRA C:2012 guidelines applied. Safety compliance: FuSa RTX code has completed stringent safety analysis and rigorous testing. The FuSa code is approved for use in applications with the most demanding Safety Integrity Levels (SIL). See FuSa RTS for the list of applicable safety standards.
Reliable execution	Time-deterministic interrupt execution: RTX utilizes the LDEX or STEX instruction The LDEX or STEX instruction is available on most Cortex-M processors therefore, user interrupts are never disabled.
Safe operation	Separate stacks for ISR or RTOS and threads - the RTOS kernel executes in handler mode with stack separated from user threads which avoids unexpected stack loads. Stack overflow checking - RTX implements a software stack overflow checking which traps stack overruns. Runtime check of kernel objects - object identifiers are validated at run-time for type-mismatches and are protected from inadvertently accesses by the user application.
Flexible memory management	Object-specific memory pools - dedicated fixed-size memory blocks for each object type avoids memory fragmentation during run-time and makes object creation and destruction time deterministic. Static object memory allocation - the user application can rely on static memory for kernel objects, which guarantees that the RTOS system can never run out of storage during run-time.
RTOS-aware debugging	Event Recorder support - all important internal FuSa RTX events can be logged and analyzed using Event Components and System Analyzer. Stack Usage Watermark - special provisions in FuSa RTS allow MDK debugger to determine during run-time the current and the maximum stack usage for each thread. Object Memory Usage Counters - built-in mechanism that helps to analyze the maximum memory usage for each RTX object type.