12 January 2017

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The 10 top differences UNIX Vs LINUX

The 10 top differences UNIX Vs LINUX
#The 10 top differences UNIX Vs LINUX:
UNIX is an operating system which was first developed in the 1960s, and has been under constant development ever since. By operating system, we mean the suite of programs which make the computer work. It is a stable, multi-user, multi-tasking system for servers, desktops and laptops.
UNIX systems also have a graphical user interface (GUI) similar to Microsoft Windows which provides an easy to use environment. However, knowledge of UNIX is required for operations which aren't covered by a graphical program, or for when there is no windows interface available, for example, in a telnet session.
  • The kernel - The kernel of UNIX is the hub of the operating system: it allocates time and memory to programs and handles the filestore and communications in response to system calls.
  • As an illustration of the way that the shell and the kernel work together, suppose a user types rm myfile (which has the effect of removing the file myfile). The shell searches the filestore for the file containing the program rm, and then requests the kernel, through system calls, to execute the program rm on myfile. When the process rm myfile has finished running, the shell then returns the UNIX prompt % to the user, indicating that it is waiting for further commands.
  • The shell - The shell acts as an interface between the user and the kernel. When a user logs in, the login program checks the username and password, and then starts another program called the shell. The shell is a command line interpreter (CLI). It interprets the commands the user types in and arranges for them to be carried out. The commands are themselves programs: when they terminate, the shell gives the user another prompt (% on our systems).
  • The adept user can customise his/her own shell, and users can use different shells on the same machine. Staff and students in the school have the tcsh shell by default.
  • The tcsh shell has certain features to help the user inputting commands.
  • Filename Completion - By typing part of the name of a command, filename or directory and pressing the [Tab] key, the tcsh shell will complete the rest of the name automatically. If the shell finds more than one name beginning with those letters you have typed, it will beep, prompting you to type a few more letters before pressing the tab key again.
  • History - The shell keeps a list of the commands you have typed in. If you need to repeat a command, use the cursor keys to scroll up and down the list or type history for a list of previous commands.

Linux - From smartphones to cars, supercomputers and home appliances, the Linux operating system is everywhere.
Android may be based on Linux, but it’s not based on the type of Linux system you may have used on your PC. You can’t run Android apps on typical Linux distributions and you can’t run the Linux programs you’re familiar with on Android.
Linux makes up the core part of Android, but Google hasn’t added all the typical software and libraries you’d find on a Linux distribution like Ubuntu. This makes all the difference.
Linux. It’s been around since the mid ‘90s, and has since reached a user-base that spans industries and continents. For those in the know, you understand that Linux is actually everywhere. It’s in your phones, in your cars, in your refrigerators, your Roku devices. It runs most of the Internet, the supercomputers making scientific breakthroughs, and the world\'s stock exchanges. But before Linux became the platform to run desktops, servers, and embedded systems across the globe, it was (and still is) one of the most reliable, secure, and worry-free operating systems available.

For those not in the know, worry not – here is all the information you need to get up to speed on the Linux platform.

What is Linux?

Just like Windows XP, Windows 7, Windows 8, and Mac OS X, Linux is an operating system. An operating system is software that manages all of the hardware resources associated with your desktop or laptop. To put it simply – the operating system manages the communication between your software and your hardware. Without the operating system (often referred to as the “OS”), the software wouldn’t function.

Also Read | Why Linux is most popular OS

The OS is comprised of a number of pieces: 

  • The Bootloader: The software that manages the boot process of your computer. For most users, this will simply be a splash screen that pops up and eventually goes away to boot into the operating system.
  • The kernel: This is the one piece of the whole that is actually called “Linux”. The kernel is the core of the system and manages the CPU, memory, and peripheral devices. The kernel is the “lowest” level of the OS.
  • Daemons: These are background services (printing, sound, scheduling, etc) that either start up during boot, or after you log into the desktop.
  • The Shell: You’ve probably heard mention of the Linux command line. This is the shell – a command process that allows you to control the computer via commands typed into a text interface. This is what, at one time, scared people away from Linux the most (assuming they had to learn a seemingly archaic command line structure to make Linux work). This is no longer the case. With modern desktop Linux, there is no need to ever touch the command line.
  • Graphical Server: This is the sub-system that displays the graphics on your monitor. It is commonly referred to as the X server or just “X”.
  • Desktop Environment: This is the piece of the puzzle that the users actually interact with. There are many desktop environments to choose from (Unity, GNOME, Cinnamon, Enlightenment, KDE, XFCE, etc). Each desktop environment includes built-in applications (such as file managers, configuration tools, web browsers, games, etc).

Applications: Desktop environments do not offer the full array of apps. Just like Windows and Mac, Linux offers thousands upon thousands of high-quality software titles that can be easily found and installed. Most modern Linux distributions (more on this in a moment) include App Store-like tools that centralize and simplify application installation. For example: Ubuntu Linux has the Ubuntu Software Center which allows you to quickly search among the thousands of apps and install them from one centralized location. 

07 January 2017

The best 15 mostly asked Java Interview Questions

1. What is JVM? Why is Java called the ‘Platform Independent Programming Language’?
htmlprojectsJVM, or the Java Virtual Machine, is an interpreter which accepts ‘Bytecode’ and executes it.
Java has been termed as a ‘Platform Independent Language’ as it primarily works on the notion of ‘compile once, run everywhere’. Here’s a sequential step establishing the Platform independence feature in Java:
  • The Java Compiler outputs Non-Executable Codes called ‘Bytecode’.
  • Bytecode is a highly optimized set of computer instruction which could be executed by the Java Virtual Machine (JVM).
  • The translation into Bytecode makes a program easier to be executed across a wide range of platforms, since all we need is a JVM designed for that particular platform.
  • JVMs for various platforms might vary in configuration, those they would all understand the same set of Bytecode, thereby making the Java Program ‘Platform Independent’.
2. What is the Difference between JDK and JRE?
When asked typical Java Interview Questions most startup Java developers get confused with JDK and JRE. And eventually, they settle for ‘anything would do man, as long as my program runs!!’ Not quite right if you aspire to make a living and career out of Programming.
The “JDK” is the Java Development Kit. I.e., the JDK is bundle of software that you can use to develop Java based software.
The “JRE” is the Java Runtime Environment. I.e., the JRE is an implementation of the Java Virtual Machine which actually executes Java programs.
Typically, each JDK contains one (or more) JRE’s along with the various development tools like the Java source compilers, bundling and deployment tools, debuggers, development libraries, etc.
3. What does the ‘static’ keyword mean?
We are sure you must be well-acquainted with the Java Basics. Now that we are settled with the initial concepts, let’s look into the Language specific offerings.
Static variable is associated with a class and not objects of that class. For example:
public class ExplainStatic {
      public static String name = "Look I am a static variable";
}
We have another class where-in we intend to access this static variable just defined.
public class Application {
        public static void main(String[] args) {
            System.out.println(ExplainStatic.name)
        }
}
We don’t create object of the class ExplainStatic to access the static variable. We directly use the class name itself: ExplainStatic.name
4. What are the Data Types supported by Java? What is Autoboxing and Unboxing?
This is one of the most common and fundamental Java interview questions. This is something you should have right at your finger-tips when asked. The eight Primitive Data types supported by Java are:
  • Byte : 8-bit signed two’s complement integer. It has a minimum value of -128 and a maximum value of 127 (inclusive)
  • Short : 16-bit signed two’s complement integer. It has a minimum value of -32,768 and a maximum value of 32,767 (inclusive).
  • Int : 32-bit signed two’s complement integer. It has a minimum value of -2,147,483,648 and a maximum value of 2,147,483,647 (inclusive)
  • Long : 64-bit signed two’s complement integer. It has a minimum value of -9,223,372,036,854,775,808 and a maximum value of 9,223,372,036,854,775,807 (inclusive)
  • Float
  • Double
Autoboxing: The Java compiler brings about an automatic transformation of primitive type (int, float, double etc.) into their object equivalents or wrapper type (Integer, Float, Double,etc) for the ease of compilation.
Unboxing: The automatic transformation of wrapper types into their primitive equivalent is known as Unboxing. (Read more)

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