Interrupts in Operating System (OS)

Interrupts are signals or events that divert the attention of the central processing unit (CPU) from its current task to handle a specific event. These events can range from hardware-related issues, such as a keypress or mouse movement, to software-generated signals like system calls or program errors. Interrupts allow the operating system to promptly respond to these events, ensuring a more dynamic and efficient system.

In the below PDF we discuss about Interrupts  in detail in simple language, Hope this will help in better understanding.

Operating System

Types of Interrupts:

1.  Hardware Interrupts:

Hardware interrupts are generated by external hardware devices to communicate with the Operating system. These interrupts indicate specific events or conditions that require attention from the system. Examples of hardware interrupts include:

  • External Interrupts: These are generated by external devices like keyboards, mice, or other peripherals to signal the CPU that they require attention.
  • Internal Interrupts: Internal events, such as a timer reaching zero or a hardware error, can trigger internal interrupts, prompting the CPU to address the situation.

2. Software Interrupts:

Software interruptions, also known as software exceptions, are generated when software components communicate with the operating system or perform certain activities. Examples of software interrupts are:

  • System calls: Software programmes generate system calls to request certain operating system functions. System calls allow user-level applications to interface with privileged operating system services like file operations.
  • Exceptions: it is created by the processor in response to extraordinary conditions or events. Examples of exceptions include division by zero, improper memory access, and illegal instructions.

How Interrupts Work:

When an interrupt occurs, the CPU suspends its current execution and transfers control to a specific interrupt handler routine. This routine is a piece of code designed to manage the interrupt’s specific type. Once the handler completes its task, the CPU resumes its previous operation. Interrupts are crucial for multitasking environments, allowing the operating system to efficiently manage multiple Processes and provide a responsive user experience.

Significance of Interrupts:

  1. Enhanced Responsiveness: Interrupts enable a system to respond promptly to external events without continuously checking for updates. This improves the overall responsiveness of the system.
  2. Multitasking: Operating systems utilize interrupts to facilitate multitasking, allowing the CPU to switch between different processes swiftly. This is essential for running multiple applications concurrently.
  3. Resource Management: Interrupts play a crucial role in managing hardware resources. They help prioritize tasks, ensuring that critical processes are attended to promptly.
  4. Real-time Processing: In real-time systems, interrupts are vital for processing time-sensitive tasks. Hardware interrupts, in particular, are instrumental in responding to external events with minimal delay.

Related Question

An interrupt is a mechanism used by hardware or software to notify the CPU that an event requiring immediate attention has occurred. It temporarily halts the normal execution of a program to handle the specific event.

Interrupts can be classified into two main types: hardware interrupts and software interrupts. Hardware interrupts are generated by external devices, while software interrupts are triggered by a specific instruction in the program.

An interrupt handler, also known as an interrupt service routine (ISR), is a special routine that is executed when an interrupt occurs. It is responsible for handling the interrupt, performing necessary actions, and then allowing the normal program execution to resume.

Interrupts are prioritized based on their importance and urgency. The operating system assigns different priority levels to various interrupts. Higher priority interrupts are serviced first, ensuring that critical tasks are addressed promptly.


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