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Modern Operating Systems by Herbert Bos and Andrew S. Tanenb...
Modern_Operating_Systems_by_Herbert_Bos_and_Andrew_S._Tanenbaum_4th_Ed.pdf
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Modern Operating Systems by Herbert Bos and Andrew...
Modern_Operating_Systems_by_Herbert_Bos_and_Andrew_S._Tanenbaum_4th_Ed.pdf-M ODERN O PERATING S YSTEMS
Modern Operating Systems by Herbert...
Modern_Operating_Systems_by_Herbert_Bos_and_Andrew_S._Tanenbaum_4th_Ed.pdf-M ODERN O PERATING S YSTEMS
Page 1060
CHAP. 12
PROBLEMS
1029
You may use up to 256 KB of RAM for tables if need be. Write a macro to carry out
your algorithm.
Extra Credit
: Write a procedure to do the computation by looping
over the 32 bits. Measure how many times faster your macro is than the procedure.
16.
In Fig. 12-8, we saw how GIF files use 8-bit values to index into a color palette. The
same idea can be used with a 16-bit-wide color palette.
Under what circumstances, if
any, might a 24-bit color palette be a good idea?
17.
One disadvantage of GIF is that the image must include the color palette, which in-
creases the file size. What is the minimum image size for which an 8-bit-wide color
palette breaks even? Now repeat this question for a 16-bit-wide color palette.
18.
In the text we showed how caching path names can result in a significant speedup
when looking up path names. Another technique that is sometimes used is having a
daemon program that opens all the files in the root directory and keeps them open per-
manently, in order to force their i-nodes to be in memory all the time. Does pinning the
i-nodes like this improve the path lookup even more?
19.
Even if a remote file has not been removed since a hint was recorded, it may have been
changed since the last time it was referenced. What other information might it be use-
ful to record?
20.
Consider a system that hoards references to remote files as hints, for example as
(name, remote-host, remote-name).
It is possible that a remote file will quietly be re-
moved and then replaced. The hint may then retrieve the wrong file. How can this
problem be made less likely to occur?
21.
In the text it is stated that locality can often be exploited to improve performance. But
consider a case where a program reads input from one source and continuously outputs
to two or more files. Can an attempt to take advantage of locality in the file system lead
to a decrease in efficiency here? Is there a way around this?
22.
Fred Brooks claims that a programmer can write 1000 lines of debugged code per year,
yet the first version of MINIX (13,000 lines of code) was produced by one person in
under three years. How do you explain this discrepancy?
23.
Using Brooks’ figure of 1000 lines of code per programmer per year, make an estimate
of the amount of money it took to produce Windows 8.
Assume that a programmer
costs $100,000 per year (including overhead, such as computers, office space, secretar-
ial support, and management overhead). Do you believe this answer?
If not, what
might be wrong with it?
24.
As memory gets cheaper and cheaper, one could imagine a computer with a big bat-
tery-backed-up RAM instead of a hard disk.
At current prices, how much would a
low-end RAM-only PC cost?
Assume that a 100-GB RAM-disk is sufficient for a low-
end machine.
Is this machine likely to be competitive?
25.
Name some features of a conventional operating system that are not needed in an em-
bedded system used inside an appliance.
26.
Write a procedure in C to do a double-precision addition on two given parameters.
Write the procedure using conditional compilation in such a way that it works on
16-bit machines and also on 32-bit machines.
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