OSI MODEL (Open System Interconnection)

The OSI model stands for Open System Interconnection.

It is a concept Model that characterizes and standardizes communication system functions of a telecommunication/Communication or computing system.

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What are the 7 layers of the OSI Model?

The 7 Layers of OSI Model are - 

Layer 7: The Application Layer

Layer 6: The Presentation Layer

Layer 5: The Session Layer.

Layer 4: The Transport Layer.

Layer 3: The Network Layer.

Layer 2: The Data-Link Layer.

Layer 1: The Physical Layer.

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DHCP (Dynamic Host Configuration Protocol)

Dynamic Host Configuration Protocol (DHCP) is a client/server protocol. It automatically provides an Internet Protocol Address (IP) host with its IP address and other related configuration information such as default gateway/Subnet mask.

Advantage of DHCP - Its make IP address Management Easier.

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Why is DHCP used?

DHCP (Dynamic Host Configuration Protocol) is a protocol used to provide quick, automatic, and central management for the distribution of IP addresses within a network. DHCP is also used to configure the proper subnet mask, default gateway, and DNS server information on the device.

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Port Number- 

Dynamic Host Configuration Protocol/Standard port  - 67

The port number 546 is used for DHCP client and 547 is used for DHCP server

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DNS (Domain Name System/Server/Service)

DNS and Example-

DNS stands for Domain Name System/Server/Service, it is an Internet service that translate/Convert the Domain Name into the IP Address so that Computer can understand the open the particular website for the search Domain Name.

Computer/Internet understand the Machine language that is binary Digits (0/1), So domain name is Easy to remember because they are alphabetic in nature.

For example, the domain name www.XYZ.com might translate to 198.115.232.0.

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How to Find the DNS - 

On Windows Platform (XP, 7, 8, 8.1, 10) systems- 

1. Open a Command Window(CMD)  (To open CMD- Select Start > Run and Enter cmd )

2. At the prompt, enter command ipconfig -all. 

From here you will all the information of your IP address, Subnet mask, DNS etc.

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Operating System Related Interview Question/Answer (Page 2)

Question 6 - What is Semaphore?

Answer 6 - SEMAPHORE-  Semaphore is a variable, whose status reports common resource.

Types- It is of two types-

1. Binary Semaphore.

2. Counting Semaphore.

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Question 7- What is Thread ?

Answer 7 - A thread is a program line under execution. Thread sometimes called a light- weight                             process, is a basic unit of CPU utilization; it comprises a thread id, a program counter, a                       register set, and a stack.

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Question 8 - What do you know about interrupt ?

Answer 8 - Interrupt can be understood as a signal from a device causing context switch.

>>  To handle interrupts, interrupt handlers or service routine are required.

>> The address of each interrupt services routine is provided in a list which is maintained in interrupt        vector.

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Question 9 - What is Context Switching ?

Answer 9 - Context is associated with each process encompassing all the information describing the                       current execution state of the process - when the OS saves the context of program that is currently running and restores the context of the next ready to run process, it is called as context switching. (It is important for multitasking OS)

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Question 10- What is Critical Section ?

Answer 10 - It is section of code which can be executed only by one process at a time.

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Operating System Related Interview Question/Answer

Question 1 - What is operating system?

Answer 1-  OPERATING SYSTEM -   An operating system is a program that acts as an                                                                                      intermediary between  user and computer hardware. 

• The purpose of an OS is to provide a convenient environment in which user can execute programs in a convenient and efficient manner.

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Question 2 -  What are the different types of operating Systems (OS) ?

Answer 2 -    The different types of operating Systems (OS) are -

1. Batched Operating system 
2. Multi- programmed Operating system.
3. Time Sharing Operating system.
4. Distributed Operating system.
5. Real-time Operating system.

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Question 3 - What is Dead lock ?

Answer 3 - DEAD- LOCK -   Deadlock is a situation or condition where the two processes are                                                            waiting for each  other to complete so that they can start. This result                                                      both processes to hang.

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Question 4 - What is process ?

Answer 4 -  A program in execution is called a process. 

Types-    There are two types of processes - 

1. Operating system processes.

2. User processes

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Question 5 -  What are the states of process ?

Answer 5 -  The states of process are - 

1. New
2. Running.
3. Waiting.
4. Ready.
5. Terminated.

                                             New >  Running  > Waiting > Ready > Terminated.

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