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1Using FCFS algorithm, which is allocated CPU first?
2	The process that requests the CPU first
3	
4In systems that support virtual memory, 
5	Physical memory is seperated from logical memory
6	
7In a system resource-allocation graph
8	A directed edge from a process to a resource is called a request edge.
9	
10The path name /home/people... is an example of
11	An absolute path name
12	
13A Microkernel is a kernel
14	that is stripped of all nonessential components
15	
16In a wait-for graph, there is only one type of node, process.
17	?True
18	
19Memory paging suffers from fragmentation, particularly external fragmentation.
20	?False
21	
22In general, virtual memory decreases the degree of multiprogramming in a system.
23	False
24	
25If a resource-allocation graph has a cycle, the system must be in a deadlocked state.
26	False
27	
28The circular-wait condition for a deadlock implies the hold-and-wait condition. 
29	True
30	
31When memory allocated to a process is slightly larger than the requested memory, space at the end of a partition is unused and wasted. This wasted space within a partition is called as internal fragmentation. When enough total memory space exists to satisfy a request, but it is not contiguous; storage is fragmented into a large number of small holes. This wasted space not allocated to any partition is called external fragmentation.
32
33Deadlock can exist if and only if 4 conditions hold simultaneously:
34	mutual exclusion, hold and wait, no preemption, circular wait
35	
36Paging is a memory-management scheme that permits the physical-address space of a process to be noncontiguous. With Paging, Physical memory is broken into fixed-sized blocks called frames. Logical memory is also broken into blocks of the same size called pages. When a process is to be executed, its pages are loaded into any available memory frames from the backing store. 
37
38Logical Vs Physical address space:-An address generated by the CPU is commonly referred to as a logical address, whereas an address as seen by the memory unit is commonly referred to as a physical address.
39
40If you were creating an operating system to handle files, there are six basic file operations that you should implement.
41	Creating, writing, reading, repositioning within a file, deleting, truncating.
42	
43Explain the sequence of events that happens when a page-fault occurs.
44	When the OS cannot load the requested page into memory, we get a page-fault. An interrupt occurs.
45	First we check if the memory reference is valid. If it is invalid, it will be terminated.
46	If it is valid, we locate a free frame, and then schedule the disk to read the page into the free frame. The page table is updated, and the instruction is attempted again with the valid page.
47	
48What is thrashing?
49	Thrashing is when a disk is being overworked by moving information between system memory and virtual memory.  As the main memory gets filled, additional pages need to be swapped in and out of virtual memory. This can result in a constant state of paging and page-faults. Thrashing occurs when the system does not have enough memory, or too much is running at the same time, or if the system has low resources.
50
51Describe the elements of a hased page table.
52	A hashed page table has values that are hashed that represent a virtual page number. Each entry in the hash table has a linked list of elements that hash to the same location. Each element has the virtual page number, the value of the coressponding page frame, and a pointer to the next element in the linked list.
53
54What is the purpose of dirty bit in page table?
55	A dity bit is an indicator as to whether it needs to be updated. It helps avoid unnecessary writes on paging devices. It is set when the processor writes to that memory. If a block of memory needs to be reaplced, its dirty bit is checked to see if the block needs to be written back to secondary memory before being replaced, or if it can just be removed. If the bit is on, the page is modified and can be replaced. If it is off, no replacement is necessary since no updates have been made.
56	
57What is extent? What is extent called in NTFS?
58	An extent is a contigious block of disks. Extents are allocated for file allocation. A file consists of one or more extents. When a file outgrows its original extent, an additional one is allocated.
59	In NTFS it is called cluster runs.
60
61Access controls protects directories. What are permissions to members of the group that owns the file?
62	Read, write, executed
63	
64Three security goals of CIA triad?
65	Confidentiality, Integrity, Availability
66
67Suppose that we have a computer system using 32-bit logical address and 46-bit physical address. It also uses paging for memory management with a single-level page table organization. The page size is 4K bytes and each page table entry is 32 bits or 4 bytes in size. Calculate the number of bits in each field in the logical address, the size in bytes of the page table, and the number of frames.
68	???
69	
70What is slack space?
71	Slack space is the leftover storage that exists on a computer's hard disk drive when a computer file does not need all the space it has been allocated by the OS.
72	
73There are six basic operations for file manipulation defiend in a modern OS. Give an approach for supporting file move in OS.
74	One approach could be
75	1. Create a new file.
76	2. Read from older file and Write to new file.
77	3. Delete older file.