I/O

- Input/output — the mechanisms through which a CPU communicates with the external world.

Input/output — the mechanisms through which a CPU communicates with the external world.

Covers storage, network, sensors, and displays.

Software triggers I/O via syscall (user-to-kernel boundary)

Hardware uses MMIO (memory-mapped registers) or DMA (direct memory access bypassing the CPU)

I/O latency often dominates real-world performance far more than raw compute speed.