The hardware interface specifies the plugs, sockets, cables and electrical signals that pass through each line between the CPU and a peripheral device or communications network. The CPU socket on the motherboard determines which CPU chips can be used in the computer. Peripheral cards, such as a display adapter or disk controller, plug into the bus on the motherboard. The most common buses are PCI and PCI Express. See PC data buses.

The most widely used hardware interface for attaching external devices to desktop and laptop computers is USB. It connects printers, cameras, music players, flash drives and auxiliary hard disk and optical drives. The FireWire interface is often used for video cameras. In addition, the IDE and SCSI interfaces are commonly used internally for disk and tape drives. The GPIB IEEE 488 standard is used for process control instruments. See plugs & sockets.

The de facto standard for connecting devices to local networks (LANs) is Ethernet, which is also used to hook up a cable or DSL modem.