Chapter 9, Problem 1E

a. What is a device register?
b. What is a device data register?
c. What is a device status register?

Program Plan Intro

To describe about a device register.

Explanation of Solution

Explanation:

Every device has an associated device register. A device register contains information about the logical address of the device. This address can be programmed manually or by the operating system. The information in the device register is used by the operating system or other equipment to find the respective device.

Example:

When a user connects a digital camera with the computer, the computer then interacts with the device register of the digital camera and uses the information in its device register to set up the digital camera.

A device register has two more associated registers namely device data register and device status register.

Program Plan Intro

To describe about a device data register.

Explanation of Solution

Explanation:

A device data register performs no actions but stores only data and other information. The other information is related to how much space is available to store the data. The device can read or write data to and from this device data register.

Using the space availability information contained in the device data register, it is easy to send or retrieve information to and from the device.

Program Plan Intro

To describe about a device status register.

Explanation of Solution

Explanation:

As the name suggests, the device status register shows the status or mode of operation of the device. If the device is busy or faces some issue while performing a task, the respective message will be displayed by its device status register.

Example:

Consider a device1 that is busy. If other device2 wants to interact with device1, the device status register of device1 will show the message that the device is busy. On the other hand, if an error occurs with the operations being performed by device1, its device status register will show an error message.