In a computer system operation, what is true about device controllers?

Device controllers are specialized hardware components that manage input and output operations for various devices, such as disk drives, printers, and network cards. Each device controller having a local buffer is true because these buffers serve as temporary storage areas that hold data being transferred to and from the device. This setup allows for efficient communication between the device and the rest of the computer system.

The local buffer helps to match the speed differences between the CPU and the I/O device. For example, while the CPU can process instructions at a much faster rate than most I/O devices can send or receive data, the buffer allows the CPU to continue executing other tasks instead of waiting for the I/O operations to complete. This mechanism enhances overall system performance and responsiveness.

In contrast, shared buffers wouldn't provide the same level of efficiency since access to a single shared buffer could lead to bottlenecks and increased contention among devices. Further, asserting that device controllers do not use buffers overlooks the critical role these buffers play in managing data flow and ensuring that the system operates smoothly. Additionally, local buffers are exclusive to device controllers and are not intended solely for the CPU. This distinction is vital for understanding how device controllers optimize data handling in a computer system.