Since the term "CPU" is generally defined as a device for software (computer program) execution, the earliest devices that could rightly be called CPUs came with the advent of the stored-program computer. The "central processing unit" term has been in use since as early as 1955. Main article: History of general-purpose CPUs EDVAC, one of the first stored-program computersĮarly computers such as the ENIAC had to be physically rewired to perform different tasks, which caused these machines to be called "fixed-program computers". Virtual CPUs are an abstraction of dynamically aggregated computational resources. Īn IC that contains a CPU may also contain memory, peripheral interfaces, and other components of a computer such integrated devices are variously called microcontrollers or systems on a chip (SoC).Īrray processors or vector processors have multiple processors that operate in parallel, with no unit considered central. The individual physical CPUs, processor cores, can also be multithreaded to create additional virtual or logical CPUs. Microprocessor chips with multiple CPUs are multi-core processors. Most modern CPUs are implemented on integrated circuit (IC) microprocessors, with one or more CPUs on a single IC chip. Principal components of a CPU include the arithmetic–logic unit (ALU) that performs arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that orchestrates the fetching (from memory), decoding and execution (of instructions) by directing the coordinated operations of the ALU, registers, and other components. The form, design, and implementation of CPUs have changed over time, but their fundamental operation remains almost unchanged. This role contrasts with that of external components, such as main memory and I/O circuitry, and specialized coprocessors such as graphics processing units (GPUs). Its electronic circuitry executes instructions of a computer program, such as arithmetic, logic, controlling, and input/output (I/O) operations. Bottom side of an Intel 80486DX2, showing its pinsĪ central processing unit ( CPU)-also called a central processor or main processor-is the most important processor in a given computer.
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