Data Buffering:

An essential task of an I/O module is data buffering. The data buffering is required due to the mismatch of the speed of CPU, memory and other peripheral devices. In general, the speed of CPU is higher than the speed of the other peripheral devices. So, the I/O modules store the data in a data buffer and regulate the transfer of data as per the speed of the devices.

In the opposite direction, data are buffered so as not to tie up the memory in a slow transfer operation. Thus the I/O module must be able to operate at both device and memory speed.

Error Detection:

Another task of I/O module is error detection and for subsequently reporting error to the processor. One class or error includes mechanical and electrical malfunctions reported by the device (e.g. paper jam). Another class consists of unintentional changes to the bit pattern as it is transmitted from devices to the I/O module.