I/O control methods: In data communications, what does the term “polling” mean when a host interacts with multiple terminals or devices?

Introduction / Context:Polling is a classic method of device servicing where a controller queries each attached device in turn to determine whether it needs attention. This is common in legacy multi-drop lines and simple embedded systems without sophisticated interrupt mechanisms.

Given Data / Assumptions:

• Multiple terminals or peripherals share a communication channel.
• The controller can either poll or use interrupts.
• We are interested in the definition of polling, not its performance trade-offs.

Concept / Approach:Polling is an inquiry cycle. The master sequentially asks each slave device if it has data or a request pending. If a device responds affirmatively, the master services it; otherwise, it moves on. This contrasts with interrupts, where devices signal the host asynchronously.

Step-by-Step Solution:

Verification / Alternative check:Protocols like HDLC derivatives and simple bus systems include polling modes where the primary station queries secondary stations.

Why Other Options Are Wrong:Error detection/correction: handled by CRCs and ARQ, not polling. Multiplexing and memory updates: describes data handling, not the inquiry mechanism. Decision analysis: unrelated to device service inquiry.

Common Pitfalls:Confusing polling with interrupt-driven I/O; assuming polling inherently corrects errors.

Final Answer:inquires to see if a terminal has any transaction to send