VE482 — Introduction to Operating Systems Assignment 8 solved

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Ex. 1 — Input/Output
1. Is it possible to scan a document and send it through a wireless network at full speed? Explain
why, why not.
2. How can an OS facilitate the installation of a new device without any need to recompile the OS
or even to reboot it?
3. In the lectures four I/O software layers were listed; in which of those four layers are the operations
a) Computing the track, sector, and head for a disk read
b) Writing command to the device registers
c) Checking is the user is allowed to use the device
d) Converting binary integers to ASCII for printing
4. A DMA controller has four channels. The controller is able to request a 32bit word every 100 nsec.
A respond takes equally long. How fats should the bus be in order to avoid being a bottleneck?
5. Briefly explain what a thin client is.
6. Describe how a hard disk is working and give a few details regarding its geometry.
7. What are differences between RAID 0, 1, 5, 6, and 10?
Ex. 2 — Multiprocessors
1. Suppose that the TSL instruction was not available for synchronizing a multiprocessor. Instead,
another instruction, SWP was provided that atomically swapped the contents of a register with a
word in memory. How could that be used to provide multiprocessor synchronisation?
2. Briefly describe virtualization and the main challenges that need to be overcome.
Ex. 3 — File systems
1. Assuming the current working directory is /usr/share/doc/mutt/examples what is the absolute
path of ../../../doc/../../lib/mutt?
2. A Unix system has 1KB blocks and 4B disk addresses. What is the maximum file size if i-nodes
contain 13 direct entries, and one single, double , and triple indirect entry each?
3. The time required to read a certain number of bytes can be approximated by summing the seek,
rotation delay and transfer time. Given a disk with mean seek time of 8 msec, a rotation rate of
15,000 rpm and 262,144 bytes per track what are the data rates for block sizes of (i) 1 KB, (ii)
2 KB and (iii) 4 KB?
Ex. 4 — Security
1. If using only lowercase letters how many possible 8 letter words can be chosen? Explain why a
password should always contain lower and uppercase letters, numbers and symbols.
2. Explain why memory dynamically allocated using malloc is sometimes random and some other
times set to 0.
3. A computer system is made of several components each featuring a different level of security.
How secure is this system?
4. Can security be achieved? Explain your answer.
Ex. 5 — Research
Write about a page on the topic of firewalls on Linux systems; include information on iptables,
ebtables, and arptables. Do not forget to reference your sources of information.
Ex. 6 — IDEA survey
Complete the IDEA survey and get a +5 bonus on the assignments.