why program exhibits that it is always partially
in memory (2 marks) Answer:- (Page 185)
Even in cases where the entire program
is needed, it may not be all needed at the same time. The ability to execute a
program that is only partially in memory confers many benefits. Running a
program that is not entirely in memory would benefit both the system and the
user.
Write the steps for
converting source code to executable form.
Answer:-
Translation of a source program in a high-level or
assembly language involves compilation and linking of the program series of
steps:
Compile/Assemble
↓
Link
↓
Load
↓
Execute
REF :: handouts Page No. 152
What do we name to address that is generated by
CPU?
Answer:- (Page 152)
An address generated by the CPU is
commonly referred to as a logical address.
Do you think that FIFO is useful? Provide at
least two reasons of justify your answer?
Answer:- (Page 58) Two common uses of FIFOs
are: In client-server applications, FIFOs are used to pass data between a
server process and client processes Used by shell commands to pass data from
one shell pipeline to another, without creating temporary files
How can a user control the Thrashing? Marks (2)
Answer:- (Page 11) In order to stop thrashing,
the degree of multiprogramming needs to be reduced. The effects of thrashing
can be reduced by using a local page replacement.
What is the basic logic of FIFO Page Replacement
Algorithm? Marks (2)
Answer:- (Page 198) A FIFO replacement
algorithm associates with each page the time when that page was brought into
memory. When a page must be replaced, the oldest page is chosen.
What is the difference between
Internal Fragmentation and External Fragmentation Marks (3)?
Answer:- Internal Fragmentation is the area
in a region or a page that is not used by the job occupying that region or
page. This space is unavailable for use by the system until that job is
finished and the page or region is released.
Defined Soft (Symbolic) Link in UNIX. Marks (3)
Answer:- (Page 228) Soft links take
care of all the problems inherent in hard links. They are flexible. You may
have soft links to directories and across file systems. However, UNIX has to
support an additional file type, the link type, and a new file is created for
every link, slowing down file operations.
Address translation with Inverted Page Table?
Marks (5)
Answer:- (Page 173) Page table size is
limited by the number of frames (i.e., the physical memory) and not process
address space. Each entry in the page table contains (pid, p). If a page ‘p’
for a process is loaded in frame ‘f’, its entry is stored at index ‘f’ in the
page table. We effectively index the page table with frame number; hence the
name inverted page table. Examples of CPUs that support inverted pages tables
are 64-bit UltraSPARC and PowerPC.
File system must keep track of free blocks on
disk. Write down the two Schemes used for it with example?
Answer:
Bit vector
Frequently, the free space list is implemented as a
bit map or bit vector. Each block is represented by 1 bit. If the block is
free, the bit is 1;if it is allocated, the bit is 0. This approach is
relatively simple and efficient in finding the first free block or n
consecutive free blocks on the disk.
Linked list (free list)
Another approach to free space management is to
link together all the free disk blocks, keeping a pointer to the first free
block in a special location on the disk and caching it in memory. The first
block contains a pointer to the next free disk block and so on. However this
scheme is not efficient. To traverse the list, we must read each block, which
requires substantial I/O time. It cannot get contiguous space easily.
What is the problem hard links creates in terms
of referential naming? How does one solve it?
When a hard link is created, a directory entry for
the existing file is created—there is still only one file. Both entries have
the same inode number. The link count is incremented by one in the inode for
the file. No hard links can be created for directories. Also hard links cannot
be established between files that are on different file systems. In UNIX, a
file is removed from the file system only if its hard link count is 0.
How page fault frequency model used to control
the thrashing
Answer:- (Page 210) Page fault frequency is
another method to control thrashing. Since thrashing has a high page fault
rate, we want to control the page fault frequency. When it is too high we know
that the process needs more frames. Similarly if the page-fault rate is too
low, then the process may have too many frames. The operating system keeps
track of the upper and lower bounds on the page-fault rates of processes. If
the page-fault rate falls below the lower limit, the process loses frames. If
page-fault rate goes above the upper limit, process gains frames. Thus we
directly measure and control the page fault rate to prevent thrashing
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