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Unformatted text preview: FIT1001 Operating Systems Solutions to FIT1001 Tutorial for LN8 Operating Systems * Exercise 1 I/O devices 1. What is the difference between the three methods used by the Operating System to interact with I/O devices? SOLUTION Polling (busy waiting) the driver (through the CPU) keeps polling the device to check if it is finished. The frequency of polling is determined by the resolution required for the device, e.g., 1 msec for a mouse. Interrupt the driver asks the device to give an interrupt when finished. The CPU is involved in the data transfer from the device to memory (the OS calls a utility that performs the transfer, this could be as small as one character). Direct Memory Access (DMA) similar to interrupt driven, but enables movement of entire blocks of data. The CPU is involved only in initiating the data transfer, and handling the interrupt at the end of the transfer. So, polling and the other two methods work differently. The difference between interrupt and DMA is more subtle. It pertains mainly to the amount of data that can be transferred without CPU intervention. 2. Describe what happens when your program has just requested the user to enter some input under the following I/O method: Polling. SOLUTION 1. The device driver starts the I/O device. 2. The calling process is suspended, and another process is started. 3. At specific intervals, the new process is stopped, and the CPU asks the device (through the device driver) if it is finished....
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This note was uploaded on 08/15/2010 for the course FIT 1001 taught by Professor Egerton during the Three '10 term at Monash.
- Three '10
- Operating Systems