Difference Between Linux and Windows

Parameter	Windows	Linux
Introduction	It is an Operating System developed by Microsoft and  named Windows on November 20, 1985 as a graphical operating system shell for MS-DOS	Linux is a Unix Like Operating System introduced by Linus Torvalds and was first released on 5 October 1991.
License Type	Proprietary Commercial Software and must have to be Purchased before using Windows OS.	Except Red Hat all versions are free and are distributed under GNU GPL License.
File System Supported	NTFS,FAT,FAT 32, ISO 9660, UDF,	Ext,Ext2, Ext3, Ext3, ReiserFS, FAT, ISO 9660, UDF, NFS, NTFS, JFS, XFS, Minux and GmailFS
Versions	Windows XP, Windows Vista, Windows 7, Windows 8, Windows 8.1 etc.	Red Hat, Suse Linux, Debian, Knoppix, Ubuntu etc.

Difference Between Windows 8 and Windows 8.1

Parameter	Windows 8	Windows 8.1
Definition	It is a Personal Computer Operating System Designed by Microsoft and is preceded by Windows 7 Operating System.	It is enhanced version of windows 8 operating system.
Start Button	Start Button is not Present in Windows 8.	Start Button is restored to task bar in Windows 8.1 to open start screen.
App  Snapping	Only two app can be snapped onto a single display.	4 Applications can be snapped onto a single display depending upon screen size.
Message App	Message App is available in Windows 8.	Message is Replaced by Skype, which allows users to accept calls directly from lock screen.

Ext, Ext2, Ext3 and Ext4 Linux File Systems

EXT (Extended File System)

 It was the first file system for Linux kernel developed by Remy Card in April 1992. It was based on metadata structure .It was the first file system that implemented VFS( Virtual File System ). Some features of this file system are as follows:
a) It supports maximum partition size up to 2 Giga Bytes.
b) It support file name size up to 255 characters long.
c) It lacked in timestamps (the current time of an event that is recorded by a computer) for modifications to inodes (a data Structure that stores all the information about a file except its name and its actual data) and to data.
d) It lacked in providing support for separate access for each user and group.
e) Linked list technique was used for file handling.

Ubuntu Installation Step by Step

Boot Your System with Ubuntu 12.10 Installation CD/DVD.

Index Allocation

It is the Disk allocation technique in which each file has its own index block which is an array of disk block addresses. The n^th entry in the index block points to n^th block of file.

Whenever a file is created its index block is initialized, free block is taken from the disk and its entry is made into index table. whenever  file uses a new block its entry is made into index table. Index table consist of the addresses of all disk blocks on which a particular file is written.

Linked Allocation

It is a disk allocation technique in which files are stored in a linked fashion and scattered way. Directory entry is used that contains pointer to first disk block of file and each block contains pointer to next block.

These Pointers are not made visible to users. Each block has 512 bytes in size out of which 4 bytes are used to store pointer and rest 508 bytes is used by the user.

This Technique has the advantage that there is no external fragmentation and files can be stored anywhere. Another advantage is that there is no need to define the size of file and it can grow as long as free blocks are available.

First Fit, Best Fit and Worst Fit Memory Allocation

Best fit Allocation: It is the Contiguous allocation technique in which file is saved on the blocks whose size is same to file size or little more than file size. E.g. if we want to save a 200 Kb file and one block of 250KB is available then it will be saved to this available block.

The advantage of using this technique is best disk utilization but has the disadvantage that it is slow. Every time we want to save a file, we have to find a space whose size is either similar to file size or is slightly more.

Another Problem Associated with this technique is that if we want to extend the file contents than it can’t be implemented.

Contiguous Allocation

It is the Memory allocation technique in which contiguous blocks of this are used to save files. Whenever a file is created its size is calculated and based upon its size contiguous blocks are allocated to it for store. This allocation can be Best Fit, Worst Fit or First Fit.

The Main Advantage of using this technique is that it provides fast file access since whole file is allocated contagious blocks.

Directory Implementation

Directory efficiency, performance and reliability are totally dependent on the technique used to store them. They are saved on Disks with two well Known Techniques:

1) Linear List: It is the Simple method of directory implementation. It makes use of a file name and a pointer to data blocks. Whenever a new file is created, whole directory is checked to make sure that no existing file has the same name. If the directory contains no file with this name it is added to the end of directory. For the deletion operation file is searched and the allocated space is released.

The Main Disadvantage is of this technique is that every time we create a new file, directory has to be checked for existing file name .The second problem is that files are accessed in a serial fashion which results in slow performance 

Demand Paging

Whenever a program is executed it is required to be loaded into main memory. This loading can be done by two methods:

1) By loading the entire program into main memory. But Problem with this technique is that if user wants to select limited options, whole program will be loaded regardless of user selection.

2) Another Approach is to load only those pages which are currently needed. “The Technique of loading in which only those pages are loaded into main memory which is currently needed is called Demand Paging”. The pages which are not required are not loaded into main memory.

Semaphores

These are like integers but has the following three difference from them:
1) Its value can be initialized as integer but only increment or decrement operations are allowed and its current value can't be read.
2) If any thread decrements its value and result is negative then thread itself can't continue until any other thread increments the Semaphore.
3) If any thread increments Semaphore and their are another threads waiting ,one of the thread gets blocked which was in waiting list.

What is Process?

 Any Program that is under execution is called a Process e.g. scanning an image is a process.

For the completion of a process resources are required. These resources are allocated to process either when process is created or is under execution. For Example you have typed a page in Microsoft Word and you want to print it, as you give print command the print process is created and it requires Printer as resource. If any other process is using the printer then your page will be queued and will be printed when first process of printing is complete. A process may have sub processes which are called child processes.A Process can demand only those resources which are available e.g. if 8 resources are available than process can demand all 8 resources but 9th resource can't be demanded.

Round-Robin Scheduling

It is the CPU Scheduling Technique specially designed  for the time shared systems. This Technique is similar to FCFS Technique but the difference is that processes are switched at a regular interval of time and the regular internal is called time quantum.The can be from 0 to 100 milliseconds.

The ready queue is used in a circular fashion. The CPU is allocated to each process for a regular interval of time of 1 time quantum each new process is added to the tail ready queue. CPU scheduling picks first process from ready queue, set a timer to interrupt after 1 time quantum and then process is dispatched.If the burst time of process is less than a time quantum then it will automatically release the CPU.The average waiting time a round Robin policy is often high.

Priority Scheduling

It is a CPU Scheduling Technique in which CPU is allocated to the process with highest priority. Equal priority processes are served in FCFS order.Priority is indicated by fixed range of numbers, it can be 0 to 10 or 0 to 1000. However there is no protocol that whether 0 will be highest priority or lowest. Some systems used lower numbers as lower priority and some systems uses lower numbers as highest priority.

Consider the following set of processes assumed to arrive at 0 in the order P1, P2 and P3 with the CPU Burst time in milliseconds.
Process             Burst time           Priority
    P1                       10                        3
    P2                       5                          1
    P3                       6                          2

Shortest Job First (SJF) CPU Scheduling

It is a CPU Scheduling Technique in which CPU is allocated to the process whose burst time is minimal.
Consider the following set of processes with the length of the CPU burst given in millisecond.
Process             Burst time
   P1                         10
   P2                          5
   P3                          1
   P4                          4

First Come First Serve (FCFS) CPU Scheduling

It is the simplest CPU scheduling algorithm in which CPU is allocated first to the process that request it first. This policy is managed by FCFS queue. When CPU is free it is allocated to the first process of the ready Queue and the running process is removed from the ready queue. The code generation for FCFS algorithm is simple. The main draw back of this technique is that average waiting time of a process is quite long.Consider the Following queue of process.

Process              Burst Time
    P1                         10
    P2                         40
    P3                         1

Functions of Operating System

1) Process Management: - Operating System allocates resources to Processes, enable processes to share and exchange information, protect the resources of each process from other processes and enable synchronization among processes. Deadlock avoidance and recovery is also function of Operating System.

2) Input / Output Management:-Assignment of various input and output devices to one or more programs is done by the operating system.

3) Memory Management: - Allocation of main memory and secondary memory to the system programs as well as user data is done by the Operating System.

4) File Management:-How files will be transferred from one device to another and how they will be saved or accessed is managed by the Operating System

5) Determine and maintain order of Jobs: - It is the Responsibility of the Operating System to decide that jobs will be completed in which order. It decides that first preference should be given to which request and which can be delayed.

Open Suse 12.2 Installation Step by Step

1)      Minimum Hardware Requirements      

• CPU: Pentium III 500 MHz or higher processor (Pentium 4 2.4 GHz or higher or any AMD64 or Intel64 processor recommended)
• RAM: 1 GB physical RAM (2 GB recommended)
• Disk Space: 5.0 GB for a normal installation (more recommended)
• Sound and Graphics Card: Most modern cards are supported

2)      DVD Installation
When you’re ready, insert the DVD and (re)start the computer. Live CD/USB installation is described below
The first thing you’ll see is this welcome screen.

Difference Between High Level and Low Level Formatting

Sr. No.	High Level Formatting	Low Level Formatting
1	High-level formatting is the process of setting up an empty file system on a disk partition or logical volume and, for PCs, installing a boot sector. It creates the file system format within a disk partition or a logical volume. This formatting includes the data structures used by the OS to identify the logical drive or partition’s contents.	Low-level formatting is the process of outlining the positions of the tracks and sectors on the hard disk, and writing the control structures that define where the tracks and sectors are. It really creates the physical format that defines where the data is stored on the disk.
2	It can be done during OS installation or new partition creation.	This is intended to be the permanent foundation of the disk, and is often completed at the factory.

Difference Between Paging and Segmentation

Characteristics	Paging	Segmentation
Definition	Paging breaks physical memory Into fixed-sized blocks called frames and logical memory into blocks of the same size called pages. When a process is to be  executed, its pages are loaded into any available memory frames from the backing store. The backing store is divided into fixed sized blocks that are of the same size as the memory frames.	Segmentation is the division of computer’s primary memory into segments or sections. In segmentation, a reference to a memory location includes a value that identifies a segment and an offset within that  segment.
Length	All pages are divided into equal length.	The size of a memory segment is generally not fixed and may be as small as a single byte.
Logical Address Space	The user specifies only a single address, which is Partitioned by the hardware into a page number and an offset.	The addresses specify both the segment name And the offset within the segment. The user therefore specifies each address by two quantities: a segment name and an offset.