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 functions. For example in, domestic appliances, cars, security systems, lighting systems or vending machines. This is different to a general purpose computer that is used to perform many different functions. For example in, a personal computer (PC) or a laptop.

Understand that every computer system is made up of sub-systems, which are made up of further sub-systems

System software provides the services that the computer requires, including operating system and utility software. Application software provides the services that the user requires. Including: managing files, handling interrupts, providing an interface, managing peripherals and drivers, managing memory, managing multitasking, providing a platform for running applications, providing system security, managing user accounts. Applications are run on the operating system. The operating system is run on the firmware. The bootloader (firmware) is run on the hardware. Including: how an interrupt is generated, how it is handled using an interrupt service routine, what happens as a result of the interrupts. Software interrupts include division by zero and two processes trying to access the same memory location. Hardware interrupts include pressing a key on the keyboard and moving the mouse.