SSC IMD SA 2017 – Question 128

Which of the following registers is written by the host to send output?

• Status
• Control
• Data-in
• Data-out

Detailed Explanation:

The correct answer is d) Data-out (डेटाआउट).

I/O Controller Registers: An I/O port or controller exposes four standard hardware registers to the host processor:

• Data-out Register: Written by the host computer to send data bytes out to the device for transmission or output.
• Data-in Register: Read by the host computer to receive input data bytes provided by the device.
• Status Register: Read by the host to inspect the device’s operational state (such as the busy bit, error bit, or data-ready flag).
• Control Register: Written by the host to issue command codes (e.g., start read, start write, reset) or configure operational modes.

Therefore, to output data to a device, the host writes directly to the data-out register.