Complex sentence: Microsoft Windows CE 3.0 is an operating system (OS) designed for embedded systems including PDAs and mobile phones, working within the constraints of the slow processors and reduced amount of memory available on these devices.
Split into simpler sentences: Microsoft Windows CE 3.0 is an operating system (OS) designed for embedded systems. It was designed for embedded use in devices including PDAs and mobile phones, working within the constraints of the slow processors and reduced amount of memory available on these devices.