Interrupt and Polling

Interrupts and Polling

Introduction

Interrupts and polling are two techniques used by computers to manage input/output (I/O) operations and interact with external devices.

Interrupts

• Definition: An interrupt is a signal to the CPU that an event has occurred and requires immediate attention.
• Types:
  • Hardware Interrupts: Generated by hardware devices, such as keyboards or network cards.
  • Software Interrupts: Generated by software, such as a divide-by-zero error.
• Handling: When an interrupt occurs, the CPU saves its current state and executes an interrupt handler or interrupt service routine (ISR).
• Advantages:
  • Efficient use of CPU cycles: Interrupts allow the CPU to focus on other tasks until an interrupt occurs.
  • Fast response to events: Interrupts enable the CPU to respond quickly to events, such as keyboard presses or network packets.
• Disadvantages:
  • Complex interrupt handling: Interrupt handling can be complex and require significant programming effort.
  • Potential for interrupt overload: If interrupts occur too frequently, the CPU may become overwhelmed and unable to handle other tasks.

Polling

• Definition: Polling is a technique where the CPU repeatedly checks the status of a device or resource to determine if it requires attention.
• Types:
  • Busy-Waiting: The CPU continuously checks the status of a device, wasting CPU cycles.
  • Periodic Polling: The CPU checks the status of a device at regular intervals.
• Advantages:
  • Simple to implement: Polling is a simple technique that requires minimal programming effort.
  • Easy to understand: Polling is a straightforward technique that is easy to understand and implement.
• Disadvantages:
  • Inefficient use of CPU cycles: Polling can waste CPU cycles and reduce system performance.
  • Potential for latency: Polling may not respond to events in a timely manner, leading to latency and delays.

Comparison of Interrupts and Polling

• Interrupts:
  • Advantages: Efficient use of CPU cycles, fast response to events.
  • Disadvantages: Complex interrupt handling, potential for interrupt overload.
• Polling:
  • Advantages: Simple to implement, easy to understand.
  • Disadvantages: Inefficient use of CPU cycles, potential for latency.

Applications

• Interrupts: Used in operating systems, device drivers, and embedded systems.