Notification of Read or Write Operation

When a read or write operation is performed in a computer system, the system needs to be notified of the operation. This is done through various methods, but the correct answer to this question is option D, which states that a special signal is sent along the BUS to notify the system of the read or write operation.

Explanation

The BUS is a communication pathway that connects all the components of a computer system. It is through this BUS that data is transferred between the various components of the system, such as the CPU, memory, and I/O devices. When a read or write operation is performed, the device that is performing the operation sends a special signal along the BUS to notify the system of the operation.

This signal is known as a bus request or bus grant signal, and it informs the system that a device wishes to use the BUS for a read or write operation. The system then grants access to the BUS, allowing the device to perform the operation.

Other methods of notifying the system of read or write operations include:

- Appending an extra bit of the address: This method involves adding an extra bit to the address of the memory location being accessed. This bit is used to indicate whether the operation is a read or a write.
- Enabling the read or write bits of the devices: This method involves enabling the read or write bits of the devices that are performing the operation. This notifies the system that a read or write operation is being performed.
- Raising an appropriate interrupt signal: This method involves raising an interrupt signal to notify the system that a read or write operation has been performed. The interrupt signal is handled by the CPU, which then performs the necessary actions.

Conclusion

In conclusion, the correct answer to this question is option D, which states that a special signal is sent along the BUS to notify the system of a read or write operation. This signal is known as a bus request or bus grant signal, and it informs the system that a device wishes to use the BUS for a read or write operation. Other methods of notifying the system include appending an extra bit of the address, enabling the read or write bits of the devices, and raising an appropriate interrupt signal.