The CPU, also known as the processor, is responsible for executing everything that happens on a mobile device. It tells the device what to do and how to do it. Its performance is measured based on the number of tasks it can complete per second, known as a cycle. For example, a 1 GHz processor can process one billion cycles per second. The higher the capacity of the processor, the smoother the performance of the phone will be. When dealing with smartphones, we come across the following terminologies: ARM, x86 (Intel), MIPS, Cortex, and A5 or A7 or A9. ARM is the name of a company that licenses their architectures (branded Cortex) with different models coming up each year, such as the A series mentioned before. Based on these architectures, chip makers release their own series of chipsets (Snapdragon, Exynos, and so on) that are used in mobile devices. Newer smartphones are powered by dual-core, quad-core, and even octa-core processors.