Computer system interfaces The devices and subsystems that allow a computer to communicate with users and with other computers are collectively known as:

Introduction / Context:
Modern systems interact with people and other devices through a variety of interfaces: keyboards, displays, network adapters, USB, serial ports, and more. The umbrella term for these pathways is input/output, abbreviated I/O.

Given Data / Assumptions:

• I/O encompasses both input (to the computer) and output (from the computer).
• CPU (central processing unit) and ALU (arithmetic logic unit) are internal processing blocks, not communication peripherals.
• Interfaces may be built-in or provided via expansion hardware.

Concept / Approach:
Classify components by function: the CPU executes instructions; the ALU performs arithmetic and logic; I/O handles data exchange at the system boundary. Anything that senses the world (input) or affects the world (output) falls under I/O.

Step-by-Step Solution:

Verification / Alternative check:
Block diagrams in textbooks show I/O subsystems on the periphery of the CPU/memory complex, interfacing through buses and controllers.

Why Other Options Are Wrong:

• CPU: Executes instructions; not the set of peripherals used for communication.
• ALU: Only a sub-block of the CPU doing arithmetic/logic.
• None of the above: Incorrect since “I/O” is standard terminology.

Common Pitfalls:
Confusing interfaces (I/O) with the protocols (USB, Ethernet). Protocols run over I/O hardware.

Final Answer:
I/O