Bus (computing)

In computer architecture, a bus (historically also called a data highway^[1] or databus) is a communication system that transfers data between components inside a computer or between computers.^[2] It encompasses both hardware (e.g., wires, optical fiber) and software, including communication protocols.^[3] At its core, a bus is a shared physical pathway, typically composed of wires, traces on a circuit board, or busbars, that allows multiple devices to communicate. To prevent conflicts and ensure orderly data exchange, buses rely on a communication protocol to manage which device can transmit data at a given time.

Buses are categorized based on their role, such as system buses (also known as internal buses, internal data buses, or memory buses) connecting the CPU and memory. Expansion buses, also called peripheral buses, extend the system to connect additional devices, including peripherals. Examples of widely used buses include PCI Express (PCIe) for high-speed internal connections and Universal Serial Bus (USB) for connecting external devices.

Modern buses utilize both parallel and serial communication, employing advanced encoding methods to maximize speed and efficiency. Features such as direct memory access (DMA) further enhance performance by allowing data transfers directly between devices and memory without requiring CPU intervention.