Programmed I/O vs Interrupt-driven I/O: Understanding the Difference

Input/Output (I/O) operations are fundamental to computer systems. They allow the system to interact with external devices such as keyboards, mice, printers, and other peripherals. Two common methods used to perform I/O operations are programmed I/O and interrupt-driven I/O. In this article, we will explore the difference between these two methods and how they are implemented.

Programmed I/O:

Programmed I/O is a simple method of performing I/O operations. In programmed I/O, the processor directly communicates with the I/O device to transfer data. This method involves the following steps:

• The processor sends a request to the I/O device to transfer data.
• The I/O device responds to the request by sending or receiving data.
• The processor waits for the I/O operation to complete before moving on to the next instruction.

Programmed I/O is a synchronous operation, which means that the processor waits for the I/O device to respond before it can execute the next instruction. This method is suitable for simple I/O operations that involve small amounts of data.

Interrupt-driven I/O:

Interrupt-driven I/O is a more sophisticated method of performing I/O operations. In this method, the processor does not wait for the I/O device to respond. Instead, the I/O device sends an interrupt signal to the processor when it is ready to send or receive data. The processor then suspends its current task and services the interrupt request. Once the interrupt request is serviced, the processor resumes its previous task.

Interrupt-driven I/O is an asynchronous operation, which means that the processor does not have to wait for the I/O device to respond. This method is suitable for complex I/O operations that involve large amounts of data.

Difference between Programmed I/O and Interrupt-driven I/O:

The main difference between programmed I/O and interrupt-driven I/O is that in programmed I/O, the processor waits for the I/O device to respond before moving on to the next instruction. In interrupt-driven I/O, the processor does not wait for the I/O device to respond. Instead, it services the interrupt request and then resumes its previous task.

In conclusion, both programmed I/O and interrupt-driven I/O are methods used to perform I/O operations. Programmed I/O is a simple method suitable for simple I/O operations that involve small amounts of data. Interrupt-driven I/O is a more sophisticated method suitable for complex I/O operations that involve large amounts of data. By understanding the difference between these two methods, developers can choose the appropriate method for their application to optimize system performance.