Also running as processes within the Linux kernel is the app runtime. Each app runs in its own instance of the Android runtime, and the core of each instance is a Dalvik Virtual Machine (VM). The Dalvik VM is a mobile-optimized virtual machine, specifically designed to run fast on the devices that Android targets. Also present at this layer, and in each app’s runtime, are the Android core libraries, such as the Android class libraries, I/O, and other similar things.