Windows Mobile-based Pocket PCs (Cont.)

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This figure shows the modularity of Windows CE 4.20 . Pocket PCs were built on top of Windows CE, which is an operating system that is modularly built. It means that the core operating system contains modules and services that are being used when building new instances of the operating system.

Windows CE is optimized for devices that have minimal storage—a Windows CE kernel may run in under a megabyte of memory. Devices are often configured without disk storage, and may be configured as a “closed” system that does not allow for end user extension (for instance, it can be burned into ROM). Windows CE conforms to the definition of a real-time operating system, with a deterministic interrupt latency. It supports 256 priority levels and provides for priority inversion. Unlike Unix-like operating systems, the fundamental unit of execution is the thread, providing for simpler, faster concurrent programming.