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What is multiprocessor system? Write down the advantages of
multiprocessor system.?
Multiprocessor systems also known as parallel systems, tightlycoupled systems are growing in importance. Such systems have two
or more processors in close communication. Multiprocessor system
have three advantage.
1. Increased throughput – by increasing the number of
processors, we expect to get more work done in less time.
2. Economy of scale – Multiprocessor systems can cost less that
equivalent multiple single-processor system, because they can
share peripherals, mass storage, and power supplies.
3. Increased reliability – if functions can be distributed properly
among several processors, then the failure of one processor
will not halt the system, only slow it down. Such system is
called graceful degradation or fault tolerance.
What is the difference between I/O bound and CPU bound process.?
I/O-bound process is one that spends more of its time doing I/O than
it spends doing computations. CPU-bound process in contrast,
generates I/O request infrequently, using more of its time doing
computations.
It is important that the long-term scheduler select a good process mix
of I/O bound and CPU bound processes. If all processes are I/O
bound, the ready queue will almost always be empty, and the shortterm scheduler will have little to do. If all processes are CPU bound,
the I/O waiting queue will almost always be empty, devices will go
unused, and again the system will be unbalanced. The system with
the best performance will thus have a combination of CPU bound and
I/O bound processes.
What is Process? Write down the states of a process.?
Process is a program in execution; process execution must progress
in sequential fashion
The state of process :
new: The process is being created
running: Instructions are being executed
waiting: The process is waiting for some event to occur
ready: The process is waiting to be assigned to a processor
terminated: The process has finished execution
Describe the differences between symmetric and asymmetric
multiprocessing.?
Multiprocessors systems in use today are of two types.
Asymmetric multiprocessing – each processor is assigned a specific
task. A master processor controls the system, the other processors
either look to the master for instruction or have predefined tasks.
Symmetric multiprocessing – each processor performs all tasks within
the operating system. SMP means that all processors are peers, no
master-slave relationship exists between processors.
What is DMA?
Device controller transfers blocks of data from buffer storage directly
to main memory without CPU intervention
List the main services provided by the operating system.?
 Program execution .
 I/O operations.
 File-system manipulation.
 Communication.
 Error detection.
What do you mean by the dispatcher?
The dispatcher is the module that gives control of the CPU to the
process selected by the short-term scheduler. This function involves
the following switching context, switching to user mode and jumping
to the proper location in the user program to restart that program.
The time it takes for the dispatcher to stop one process and start
another running is known as the dispatch latency.
Why do some systems store the operating system in firmware, and
others on disk?
For certain devices, such as handheld PDAs and cellular telephones,
a disk with a file system may be not be available for the device. In this
situation, the operating system must be stored in firmware
What is bootstrap program? How could a system be designed to
allow a choice of operating systems to boot from?
The procedure of starting a computer by loading the kernel is known
as booting the system. On most computer system, a small piece of
code known as the bootstrap program, or bootstrap loader, locates
the kernel, loads it into main memory, and starts it execution.
Consider a system that would like to run both Windows XP and three
different distributions of Linux (e.g., RedHat, Debian, and Mandrake).
Each operating system will be stored on disk. During system boot-up,
a special program (which we will call the boot manager) will
determine which operating system to boot into. This means that
rather initially booting to an operating system, the boot manager will
first run during system startup. It is this boot manager that is
responsible for determining which system to boot into. Typically boot
managers must be stored at certain locations of the hard disk to be
recognized during system startup. Boot managers often provide the
user with a selection of systems to boot into; boot managers are also
typically designed to boot into a default operating system if no choice
is selected by the user.
When a process creates a new process using the fork() operation,
which of the state among Stack, Heap and Shared memory segments
is shared between the parent process and the child process?
Only the shared memory segments are shared between the parent
process and the newly forked child process. Copies of the stack and
the heap are made for the newly created process.
What is the purpose of the command interpreter? Why is it usually
separate from the kernel?
It reads commands from the user or from a file of commands and
executes them, usually by turning them into one or more system
calls. It is usually not part of the kernel since the command interpreter
is subject to changes.
What do you mean by Producer-Consumer Problem? Suggest a
solution.
A producer process continually adds new items to the buffer, each
new item being placed at the position referenced by the cursor in.
However, if the buffer is full the producer process must be blocked
when it attempts to add an item. The blocked process should be
allowed to complete its operation when the space becomes available.
after adding an item the producer increments cursor in.
A consumer process continually removes items from the buffer. after
removing an item the cursor increments the cursor out. If the buffer is
empty a process which attempts to take something out of it is
blocked. When a fresh item becomes available, the consumer should
be allowed to resume operation.
One solution to the producer-consumer problem uses shared
memory.
What system calls have to be executed by a command interpreter or
shell in order to start a new process?
In Unix systems, a fork system call followed by an exec system call
need to be performed to start a new process. The fork call clones the
currently executing process, while the exec call overlays a new
process based on a different executable over the calling process.
What the differences are between commit operations and abort
operation?
A commit operation signifies that the transaction has terminated its
execution successfully, whereas an abort operation signifies that the
transaction has ended its normal execution due to some logical error
or a system failure.
What is aging?
Aging: gradual increase of priority with age of job, to prevent
starvation is called aging.
A deadlock situation can arise if the following four conditions hold
simultaneously in a system. What are those four conditions?
Mutual exclusion: only one process at a time can use a resource.
Hold and wait: a process holding at least one resource is waiting to
acquire additional resources held by other processes.
No preemption: a resource can be released only voluntarily by the
process holding it, after that process has completed its task.
Circular wait: there exists a set {P0, P1, …, P0} of waiting processes
such that P0 is waiting for a resource that is held by P1, P1is waiting
for a resource that is held by P2, …, Pn–1is waiting for a resource
that is held by Pn, and P0is waiting for a resource that is held by P0
What is the purpose of system calls?
Allow user-level processes to request services of the operating
system.
What is CPU burst and I/O burst?
CPU burst is time interval when a process uses CPU only.
I/O burst is time interval when a process uses I/O devices only.
What do you mean by the RPC and RMI.?
A remote procedure call (RPC) is a call to procedure located on
machine that is different (remote) from the machine from which the
call was made. An PRC system consists of a communication
protocol, which typically sits on top of a transport-level service such
as the ARPA.
Remote method invocation (RMI) is a java mechanism similar to
PRCs. RMI allows a java program on one machine to invoke a
method on remote object.
Explain the differences, in terms of cost, among the three storage
types volatile, nonvolatile, and stable.?
Volatile storage refers to main and cache memory and is very fast.
However, volatile storage cannot survive system crashes or powering
down the system.
Disks and tapes are example of nonvolatile storage. Recently, USB
devices using erasable program read-only memory (EPROM) have
appeared providing nonvolatile storage. Stable storage refers to
storage that technically can never be lost as there are redundant
backup copies of the data (usually on disk).
Consider a logical address space of eight pages of 1024 words each,
mapped onto a physical memory of 32 frames.
a. How many bits are there in the logical address?
Logical address: 13 bits
b. How many bits are there in the physical address?
Physical address: 15 bits
Under what circumstances do page faults occur?
A page fault occurs when an access to a page that has not been
brought into main memory takes place.
What system calls have to be executed by a command interpreter or
shell in order to start a new process?
In Unix systems, a fork system call followed by an exec system call
need to be performed to start a new process. The fork call clones the
currently executing process, while the exec call overlays a
based on a different executable over the calling process
What are interpreters?
It run source program directly. They do not produce object program
(in machine language). Interpreters are popular in program
development environment. Interpreters are slower than compiled
codes as they translate every instruction every time the program is
executed.
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