The CPU processes instructions and data that are input into the computer so that the result can be output. A microprocessor is a type of integrated circuit on a single chip. Including: units: arithmetic logic unit (ALU) and control unit (CU); registers: program counter (PC), memory address register (MAR), memory data register (MDR), current instruction register (CIR) and accumulator (ACC); buses: address bus, data bus and control bus. How instructions and data are fetched from random access memory (RAM) into the CPU, how they are processed using each component and how they are then executed. Storing data and addresses into specific registers. Using buses to transmit data, addresses and signals. Using units to fetch, decode and execute data and instructions. The number of cores, size of the cache and speed of the clock can affect the performance of a CPU. An instruction set is a list of all the commands that can be processed by a CPU, and the commands are machine code. An embedded system is used to perform a dedicated function. For example, in domestic appliances, cars, security systems, lighting systems or vending machines. This is different from a general-purpose computer that is used to perform many different functions. For example, in a personal computer (PC) or a laptop.

Primary storage is directly accessed by the CPU. Including the role of random access memory (RAM) and read only memory (ROM). Including why a computer needs both RAM and ROM, and the difference between them. Secondary storage is not directly accessed by the CPU and is necessary for more permanent storage of data. Magnetic storage uses platters which are divided into tracks and sectors. Data is read and written using electromagnets. Including hard disk drive (HDD). Optical storage uses lasers to create and read pits and lands. Including: CD, DVD and Blu-ray. Solid-state (flash memory) uses NAND or NOR technology. Transistors are used as control gates and floating gates. Including: solid-state drive (SSD), SD card and USB drive. Pages of data are transferred between RAM and virtual memory when needed. Cloud storage can be accessed remotely in comparison to storing data locally. Physical servers and storage are needed to store data in cloud storage.