Solution:

What is programmed I/O?

• Programmed I/O is one of the three techniques we use for I/O transfer.

• In programmed I/O the processor repeatedly checks a status flag to achieve the required synchronization between the processor and an input or output device.

• If we talk of programmed I/O, it is the responsibility of the processor to control the transfer from I/O to main memory as input and from main memory to I/O as output.

programmed I/O:

• If the processor is faster than the I/O module, this is wasteful of processor time. The overall operation of the programmed I/O can be summaries as follow,

• The processor then executes that instruction by issuing a command to the appropriate I/O module.

• The I/O module will perform the requested action based on the I/O command issued by the processor and set the appropriate bits in the I/O status register.

• The processor will periodically check the status of the I/O module until it find that the operation is complete.

What is DMA?

• DMA is a combinatorial calculation principle for managing the memory buckets which, along with the weighing buckets and enable the most effective weighing combination to be found.

• DMA requests a memory cycle through the memory bus when the transfer is made.

Direct Memory Access (DMA):

• DMA can save processing time and is a more efficient way to move data from the computer’s memory to other devices.

• It's implemented in computer bus architectures to speed up computer operations and allow multitasking.

• Synchronous DMA moves a byte or word at a time between system memory and a peripheral. After completing each transfer, the DMA asks the I/O port to signal when the latter is ready for another transaction.

• In this set-up, the DMA and the CPU shares the bus cycles, with the
  DMA winning any contest for system bus control.