In computer system organization, are I/O devices and the CPU able to execute simultaneously?

In computer system organization, the CPU and I/O devices typically do not execute simultaneously in a way that both can perform processing tasks at the same time. The CPU handles computational tasks, while I/O devices manage data exchange with external sources such as disks, keyboards, or network interfaces. When a process requests data from an I/O device, the CPU often has to wait for the I/O operation to complete.

While I/O operations can overlap with CPU processing in certain scenarios through techniques known as "overlapping I/O" or "asynchronous I/O," these do not equate to true simultaneous execution. In these techniques, the CPU can continue processing other instructions while waiting for I/O operations to complete, but the I/O device cannot perform its operations and process data independently of the CPU's control. In essence, the actual execution of tasks is serialized to prevent conflicts and ensure accuracy in data handling.

This is why some other answer choices might suggest certain exceptions; however, they don't capture the fundamental principle that I/O devices and CPUs don't genuinely operate simultaneously in the strictest sense.