Explain different types of I/O commands.

When the address of a particular I/O device is placed in the address lines, at the time the processor also provide a function code in the control lines, which is referred to as a I/O command. the different types of I/O commands are:

·         Control command: The name of the command itself suggest that it includes control bits. The control command specifies the control bit that controls the I/O device physically. It mentions how the work has to be carried out and under what circumstances.

·         Status command: This command is used to check several conditions in the I/O devices and the interface for the transfer of information. This command is very useful to check the errors, completion of transfer and interrupts.

·         Output command: The output command is responsible for transfer of data from the system to the output device. It causes the transfer of information to the interface registers and then under certain satisfactory condition the information is output via output devices.

·         Input command: The input command deals with the transfer of data from the interface registers to the system. The interface places the data on the data lines under suitable conditions and then it is accepted by the processor.