Wednesday, November 5, 2014

Buffering and Interrupts

What is buffering?
Its an area of memory thats used in-between a slow and fast device to make sure the device receives information more slowly. The data is temporarily stored there while the secondary storage device receives it. This allows the processor to carry out other processors while the data is being received by the slower device.

Example: When we click on a video, the video does not start automatically meaning we have to wait for the video to load, that is when it is buffering. When it is buffering, there is enough data being transformed to the CPU so that there would be enough data for the video to run smoothly.

1) can run videos more smoothly
2)The quality remains fairly high

1) Increases loading time therefore it increases the waiting time for the video to load.
2) Synchronisation issue
3) Its going to use resources in the computer eg GPU/RAM

1) When the buffer needs service, it sends a signal to the CPU needing assistance to transfer the data to the output which means the buffer interrupts the CPU which means the CPU stops what ever processes it doing and goes and fetches the data and fills up the buffer.
2) Error messages are interrupts which means we have to respond to it.

An interrupt is a signal to the CPU to pause what its doing on that point so that it could service the interrupt and then go back to what is it doing.

Key Points 
1) Data sent to buffer from primary memory
2) This allows processor can continue with other tasks
3) Interrupts sent when buffer is full
4) Buffer is emptied to storage device
5) Buffer used to allow RAM and secondary storage device to transfer data as they do so at different       speeds
6) when buffer is empty
7) Interrupt is sent to processor
8) To request buffer refill
9) Process cycles until al data is transferred.

1)Raw facts and figuers
2)No structure or content 

1)Structured organised data
2)Processed data

Eg Bar Code, the computer identifies the number in the data base, identifies what is it and matches the price.

Magnetic Ink Recognition
1) the computer can recognise the ink's shape and read it accurately.

Optical Character Recognition
1) Captures images then it compares the shapes that has been captured with the data that is stored.

Optical Mark Recognition
1) The machine captures the marks that are on sheets that are in certain places and sends the co-ordinates to the data base.

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