Answer to Question #298568 in Computer Networks for Ella baby

Question

Discuss the three input-output communication techniques that are used in computer systems.

Answer 1

There are three primary I/O communication techniques in a computer system: programmed I/O, Interrupt-initiated I/O and direct memory access (DMA) I/O.

Programmed I/O

In this technique, the CPU remains in the loop until it receives a ready signal from the I/O device. In essence, the device does not have direct access to the memory and has to rely on programmed instructions. As such, the approach is time-consuming and wastes CPU time. 

Interrupt-initiated I/O

Like in the case of programmed I/O, the I/O device has no direct link to the memory and relies on signals. However, for this case, the CPU will issue a read command to the I/O and take up some other tasks instead of waiting in the program loop. The I/O device will send an interrupt signal to the CPU, which then checks to confirm if the I/O's device status has changed to the ready state. If ready, the CPU reads the data from the device, copies it to the memory and continues to other tasks. 

Direct Memory Access (DMA)

 Unlike in the first two cases, the DMA technique is characterized by a direct link between the I/O device and the main memory. The technique offers better speeds as compared to the first two techniques.