How Data Moves Inside a Machine

The roads and traffic signals inside your computer: what a bus is, how the CPU reads and writes RAM by address, how it reaches out to devices, and how interrupts let a device get the CPU's attention the instant something happens.

1. Buses & Addresses A bus is shared wiring that carries data between components; every byte of RAM has its own number (an address); and the CPU reads and writes memory by putting an address on the bus and saying read or write.
2. How the CPU Talks to Devices (I/O) The CPU reaches devices the same way it reaches RAM - over buses - using memory-mapped I/O or port I/O; and DMA lets a device move data to and from RAM on its own, so the CPU isn't tied up copying every byte.
3. Interrupts - Getting the CPU's Attention Instead of the CPU constantly checking whether a device is ready (polling), an interrupt is a signal that makes the CPU pause what it's doing and handle the event the instant it happens - which is what makes a computer feel responsive.