OS ass 4 - (5x1=5 1 Describe the different functions of...

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(5x1=5) 1. Describe the different functions of Direct Memory Accesses (DMA) and its six steps Process to transfer data with suitable diagram. Used to avoid programmed I/O (one byte at a time) for large data movement Requires DMA controller Bypasses CPU to transfer data directly between I/O device and memory OS writes DMA command block into memory Source and destination addresses Read or write mode Count of bytes Writes location of command block to DMA controller Bus mastering of DMA controller – grabs bus from CPU When done, interrupts to signal completion
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2. Write a detail notes about revocation of access rights in system protection Various options to remove the access right of a domain to an object o Immediate vs. delayed o Selective vs. general o Partial vs. total o Temporary vs. permanent Access List – Delete access rights from access list o Simple – search access list and remove entry o
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