Interrupts are signals that inform the CPU to cease its current activities and address a high-priority task. They are essential for efficient CPU operation, allowing it to respond quickly to various events without being idle or continuously polling for signals. Interrupts can originate from both hardware devices and software programs, prompting the operating system to take appropriate action.

Hardware Interrupts

Hardware interrupts are generated by external devices like keyboards, mice, or I/O devices. When a user interacts with a device, it sends a signal to the CPU to perform a specific action. These interrupts are further categorized into:

• Maskable Interrupts: These can be delayed if a higher priority interrupt is being serviced by the CPU. They are so named because they can be "masked" or ignored temporarily.

• Non-Maskable Interrupts (NMI): These cannot be delayed and must be processed immediately. They are critical and usually signal emergencies that the CPU must address promptly.

Software Interrupts

Software interrupts are triggered by programs when they need the CPU to execute a system call or when an exception occurs during program execution. These are divided into:

• Normal Interrupts: Caused by software instructions, these interrupts signal the CPU to perform a routine task.

• Exceptions: These are unexpected events, such as division by zero or invalid memory access, that disrupt the normal flow of program execution.

Interrupt Handling Process

When an interrupt occurs, the CPU follows a specific process to handle it:

1. Interrupt Occurrence: The CPU detects an interrupt signal.

2. Program Counter Storage: The address of the current instruction is saved.

3. Service Routine Execution: The CPU executes the interrupt service routine (ISR) associated with the interrupt.

4. Resume Execution: After the ISR is completed, the CPU resumes the interrupted program from where it left off.

Types of Software-Generated Interrupts

Software-generated interrupts can be intentional, such as system calls, or unintentional, like exceptions. System calls are used by programs to request services from the operating system, while exceptions occur due to errors during program execution.

Interrupt Latency

Interrupt latency refers to the time taken by the CPU to start processing an interrupt after it has been generated. Minimizing latency is crucial for real-time systems where timely response to interrupts is essential.

Conclusion

Interrupts are a vital mechanism that allows the CPU to handle multiple tasks efficiently. They can be generated by both hardware and software, each with its own set of handling procedures. Understanding the types and handling of interrupts is crucial for system performance and responsiveness.