Desktop personal computers have a monitor, a keyboard, a mouse, and a computer case. The personal computer is one of the most common types of computer due to its versatility and relatively low price. Types of computer systems Personal computer Basic hardware components of a personal computer, including a monitor, a motherboard, a CPU, a RAM, two expansion cards, a power supply, an optical disc drive, a hard disk drive, a keyboard and a mouse Inside a custom-built computer: power supply at the bottom has its own cooling fan This is referred to as the Von Neumann bottleneck and often limits the performance of the system. The meaning of the term has evolved to mean a stored-program computer in which an instruction fetch and a data operation cannot occur at the same time because they share a common bus. This describes a design architecture for an electronic digital computer with subdivisions of a processing unit consisting of an arithmetic logic unit and processor registers, a control unit containing an instruction register and program counter, a memory to store both data and instructions, external mass storage, and input and output mechanisms. The template for all modern computers is the Von Neumann architecture, detailed in a 1945 paper by Hungarian mathematician John von Neumann. Main articles: Von Neumann architecture and Stored-program computer Von Neumann architecture scheme
