Computer based commonly asked viva question answer

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Computer based commonly asked viva question answer

Top 30 Viva Questions & Answers for Java Developers:

1.What is JVM?
The Java interpreter along with the run time environment required to run the Java application in called as Java virtual machine(JVM)

 2. What is the most important feature of Java?
Java is a platform independent language.

3. What do you mean by platform independence?
Platform independence means that we can write and compile the java code in one platform (eg Windows) and can execute the class in any other supported platform eg (Linux,Solaris,etc).

 4. What is the difference between a JDK and a JVM?
JDK is Java Development Kit which is for development purpose and it includes execution environment also. But JVM is purely a run time environment and hence you will not be able to compile your source files using a JVM.

5. What is the base class of all classes?
java.lang.Object

 6. What are the access modifiers in Java?
There are 3 access modifiers. Public, protected and private, and the default one if no identifier is specified is called friendly, but programmer cannot specify the friendly identifier explicitly.

 7. What is are packages?
 A package is a collection of related classes and interfaces providing access protection and namespace   management.

 8. What is meant by Inheritance and what are its advantages?
 Inheritance is the process of inheriting all the features from a class. The advantages of inheritance are reusability  of code and accessibility of variables and methods of the super class by sub classes.

 9. What is the difference between superclass and subclass?
 A super class is a class that is inherited whereas sub class is a class that does the inheriting.

 10. What is an abstract class?
 An abstract class is a class designed with implementation gaps for sub classes to fill in and is deliberately  incomplete.

 11. What are the states associated in the thread?
 Thread contains ready, running, waiting and dead states.

 12. What is synchronization?
 Synchronization is the mechanism that ensures that only one thread is accessed the resources at a time.

 13. What is deadlock?
 When two threads are waiting each other and can’t precede the program is said to be deadlock.

 14. What is an applet?
 Applet is a dynamic and interactive program that runs inside a web page displayed by a java capable browser

 15. What is the lifecycle of an applet?
init() method - Can be called when an applet is first loaded
start() method - Can be called each time an applet is started.
paint() method - Can be called when the applet is minimized or maximized.
stop() method - Can be used when the browser moves off the applet’s page.
destroy() method - Can be called when the browser is finished with the applet.

 16. How do you set security in applets?
  using setSecurity Manager() method

 17. What is a layout manager and what are different types of layout managers available in java AWT?
 A layout manager is an object that is used to organize components in a container. The different layouts are    available are FlowLayout, BorderLayout, CardLayout, GridLayout and GridBagLayout

 18. What is JDBC?
 JDBC is a set of Java API for executing SQL statements. This API consists of a set of classes and interfaces to  enable programs to write pure Java Database applications.

 19. What are drivers available?
 a) JDBC-ODBC Bridge driver b) Native API Partly-Java driver
 c) JDBC-Net Pure Java driver d) Native-Protocol Pure Java driver

 20. What is stored procedure?
Stored procedure is a group of SQL statements that forms a logical unit and performs a particular task. Stored Procedures are used to encapsulate a set of operations or queries to execute on database. Stored procedures can be compiled and executed with different parameters and results and may have any combination of input/output parameters.

 21. What is the Java API?
The Java API is a large collection of ready-made software components that provide many useful capabilities, such as graphical user interface (GUI) widgets.

 22. Why there are no global variables in Java?
Global variables are globally accessible. Java does not support globally accessible variables due to following reasons:
1)The global variables breaks the referential transparency
2)Global variables creates collisions in namespace.

 23. What are Encapsulation, Inheritance and Polymorphism?
 Encapsulation is the mechanism that binds together code and data it manipulates and keeps both safe from outside interference and misuse. Inheritance is the process by which one object acquires the properties of another object. Polymorphism is the feature that allows one interface to be used for general class actions.

 24. What is the use of bin and lib in JDK?
Bin contains all tools such as javac, appletviewer, awt tool, etc., whereas lib contains API and all packages.

 25. What is method overloading and method overriding?
Method overloading: When a method in a class having the same method name with different arguments is said to be method overloading. Method overriding : When a method in a class having the same method name with same arguments is said to be method overriding.

 26. What is the difference between this() and super()?
this() can be used to invoke a constructor of the same class whereas super() can be used to invoke a super class constructor.

 27. What is Domain Naming Service(DNS)?
It is very difficult to remember a set of numbers(IP address) to connect to the Internet. The Domain Naming Service(DNS) is used to overcome this problem. It maps one particular IP address to a string of characters. For example, www. mascom. com implies com is the domain name reserved for US commercial sites, moscom is the name of the company and www is the name of the specific computer, which is mascom’s server.

 28. What is URL?
URL stands for Uniform Resource Locator and it points to resource files on the Internet. URL has four components: http://www. address. com:80/index.html, where http - protocol name, address - IP address or host name, 80 - port number and index.html - file path.

 29. What is RMI and steps involved in developing an RMI object?
Remote Method Invocation (RMI) allows java object that executes on one machine and to invoke the method of a Java object to execute on another machine. The steps involved in developing an RMI object are: a) Define the interfaces b) Implementing these interfaces c) Compile the interfaces and their implementations with the java compiler d) Compile the server implementation with RMI compiler e) Run the RMI registry f) Run the application.

30. What is RMI architecture?
RMI architecture consists of four layers and each layer performs specific functions: a) Application layer - contains the actual object definition. b) Proxy layer - consists of stub and skeleton. c) Remote Reference layer - gets the stream of bytes from the transport layer and sends it to the proxy layer. d) Transportation layer - responsible for handling the actual machine-to-machine communication.

Tricky C Language VIVA Questions with Answers:

1)Who invented C Language?
Dennis Ritchie in 1972 developed a new language by inheriting the features of both BCPL and B and adding additional features. He named the language as just C.

2) Who invented B Language?
Ken Thomson at AT&T Bell Labs developed a language and named it B. Even the B language was found to have some short comings to support development of both business applications and system software.

3) Who invented BCPL Language?
Basic Combined Programming Language(BCPL) was developed by Martin Richards, Cambridge university.

4) Why C Language?
C is one of the high level languages. It is a general purpose language, which means it can be used to write programs of any sort.

5) What are the features of C Langauges?
In C one can write programs like that of high level languages as in COBOL, BASIC, FORTRAN etc. as well as it permits very close interaction with the inner workings of the computer.
It is a general purpose programming language. It is usually called system programming language but equally suited to writing a variety of applications.
It supports various data types.
It follows the programming style based on fundamental control flow constructions for structured programming.
Functions may be pre–defined or user defined and they may return values of basic types, structures, unions or pointers.

 6)What are the advantages of c language?
Easy to write
Rich set of operators and functions that are built–in
Support for bit–wise operation
Flexible use of pointers
Direct control over the hardware
Ability to access BIOS/DOS routines
Interacting using Interrupts
Ability to write TSR programs
Ability to create .COM files
Ability to create library files (.LIB)
Ability to write interface programs
Incorporating assembly language in C program

7) What are the disadvantages of c langauge?
C is considered difficult to learn
Because of its conciseness, the code can be difficult to follow
It is not suited to applications that require a lot of report formatting and data file manipulation.

 8) What are the salient features of c languages?
The following are the salient features of C language are :
C is called a middle level language
C supports structured design approach
C is extensible
C is rich in data types and operators
C is portable

 9) What is a header file?
Header files provide the definitions and declarations for the library functions. Thus, each header file contains the library functions along with the necessary definitions and declarations. For example, stdio.h, math.h, stdlib.h, string.h etc.

10) What is character set?
Character set is the set of characters allowed and supported in the programming language. Generally a program is a collection of instructions, which contain groups of characters. Only a limited set of characters is allowed to write instructions in the program.

11) What is C token?
The smallest individual units of a C program are known as tokens.

12) List the different types of C tokens?
Constants
Identifiers
Keywords
Operators
Special symbols
Strings

13) What is a string?
A string is a sequence of characters ending with NUL. It can be treated as a one–dimensional array of characters terminated by a NUL character.

14) What are qualifiers?
Qualifiers or modifiers are identifiers that may precede the scalar data types (except float) to specify the number of bits used for representing the respective type of data in memory. The qualifiers in C are short, long, signed, and unsigned.

15) What is a function?
A function is a set of statements to perform a specific task.

16) What is a constant?
A constant is a value that does not change during the program execution. A constant used in C does not occupy memory.

17) What are the different types of constants?
There are five types of constants. They are :
Integer constants
Floating point constants
Character constants
String literals
Enumeration constants

18) What is variable?
An identifier is used to identify and store some value. If the value of the identifier is changed during the execution of the program, then the identifier is known as variable.

19) What are the rules for the identifier?
The first character must be an alphabet or underscore (_)
Digits may be included in the variable
The maximum number of characters in a word are 32 (It may vary depending upon the platform)
No other special characters are allowed.

 20) What are global variables?
Global Variables are those, which are required to be acccessed by all the functions defined after their declaration. So, the variables declared before the main {) can be acccessed by all the functions, which follow their declaration.

21) What is a keyword?
Keywords are those words of C which have predefined meaning assigned by the C language. They form a part of the database required by the C compiler.

22) What are the different types of c instructions?
There are basically three types of instructions in C are :
Type Declaration Instruction
Arithmetic Instruction
Control Instruction

 23) What is an expression?
Expression is defined as a combination of operands and operators to obtain some computation. Operands represent variables or values and The operator tells is what operation to be performed.

24) What are the types of data files?
There are two types of data files :
stream oriented or standard data files
system oriented or low level data files

 25) Why C is called a middle level language?
C combines the features of both Assembly Level Languages (Low Level Languages) and Higher Level Languages. For this reason, C is referred to as a Middle Level Language. The feature of ALLs is that of enabling us to develop system level programs and the features of HLLs are those of higher degree of readability and machine independence.

26) How can variables be characterized?
The variables can be categorized by storage class as well as by data type. The storage class specifies the portion of the program within which the variables are recognized.

27) Give the rules for variable declaration?
The rules for variable declaration in C are given below :
A variable name consists of alphabets, digits and the underscore (_) character
The length of variable should be kept upto 8 characters though your system may allow upto 40 characters
They must begin with an alphabet
Some systems also recognize an underscore as the first character
White space and commas are not allowed
Any reserved word (keyword) cannot be used as a variable name.

28) What is the purpose of type declarations?
The type declaration allow to create a synonym for other data types. Its syntax is type def type identifier; The declaration type def unsigned long int INTEGER

29) What is recursion?
C language a function may call another function. When a function calls itself, it is referred to as recursive call and the process is known as recursion. C provides very good facilities for recursion.

30) What is data types?
Data types refer to the classes of data that can be manipulated by C programs. The three fundamental data types supported by C are character, integer and real type.

Latest Digital image processing Viva Questions and Answers:

1. Define Image?
An image may be defined as two dimensional light intensity function f(x, y) where x and y denote spatial co-ordinate and the amplitude or value of f at any point (x, y) is called intensity or gray scale or brightness of the image at that point.

2. What is Dynamic Range?
The range of values spanned by the gray scale is called dynamic range of an image. Image will have high contrast, if the dynamic range is high and image will have dull washed out gray look if the dynamic range is low.

3. Define Brightness?
Brightness of an object is the perceived luminance of the surround. Two objects with different surroundings would have identical luminance but different brightness.

4. What do you meant by Gray level?
Gray level refers to a scalar measure of intensity that ranges from black to grays and finally to white.

5. What do you meant by Color model?
A Color model is a specification of 3D-coordinates system and a subspace within that system where each color is represented by a single point.

6. List the hardware oriented color models?
1. RGB model
2. CMY model
3. YIQ model
4. HSI model

7. What is Hue and saturation?
Hue is a color attribute that describes a pure color where saturation gives a measure of the degree to which a pure color is diluted by white light.

8. List the applications of color models?
1. RGB model--- used for color monitors & color video camera
2. CMY model---used for color printing
3. HIS model----used for color image processing
4. YIQ model---used for color picture transmission

9. What is Chromatic Adoption?
The hue of a perceived color depends on the adoption of the viewer. For example,the American Flag will not immediately appear red, white, and blue of the viewer has been subjected to high intensity red light before viewing the flag. The color of the flag will appear to shift in hue toward the red component cyan.

10. Define Resolutions?
Resolution is defined as the smallest number of discernible detail in an image.Spatial resolution is the smallest discernible detail in an image and gray level resolution refers to the smallest discernible change is gray level.

11. What is meant by pixel?
A digital image is composed of a finite number of elements each of which has a particular location or value. These elements are referred to as pixels or image elements or picture elements or pixls elements.

12. Define Digital image?
When x, y and the amplitude values of f all are finite discrete quantities , we call the image digital image.

13. What are the steps involved in DIP?
1. Image Acquisition
2. Preprocessing
3. Segmentation
4. Representation and Description
5. Recognition and Interpretation

14. What is recognition and Interpretation?
Recognition means is a process that assigns a label to an object based on the information provided by its descriptors.Interpretation means assigning meaning to a recognized object.

15. Specify the elements of DIP system?
1. Image Acquisition
2. Storage
3. Processing
4. Display

16. List the categories of digital storage?
1. Short term storage for use during processing.
2. Online storage for relatively fast recall.
3. Archival storage for infrequent access.

17. What are the types of light receptors?
The two types of light receptors are
• Cones and
• Rods

18. Differentiate photopic and scotopic vision ?
Photopic vision Scotopic vision
1. The human being can resolve the fine details with these cones because each one is connected to its own nerve end.
2. This is also known as bright light vision.

19. How cones and rods are distributed in retina?
In each eye, cones are in the range 6-7 million and rods are in the range 75-150 million.

20. Define subjective brightness and brightness adaptation?
Subjective brightness means intensity as preserved by the human visual system.Brightness adaptation means the human visual system can operate only from scotopic to glare limit. It cannot operate over the range simultaneously. It accomplishes this large variation by changes in its overall intensity.

21. Define weber ratio?
The ratio of increment of illumination to background of illumination is called as web er ratio.(ie) Δi/i
If the ratio (Δi/i) is small, then small percentage of change in intensity is needed (ie) good brightness adaptation.
If the ratio (Δi/i) is large , then large percentage of change in intensity is needed (ie) poor brightness adaptation.

22. What is meant by mach band effect?
Mach band effect means the intensity of the stripes is constant. Therefore it preserves the brightness pattern near the boundaries, these bands are called as mach band effect.

23. What is simultaneous contrast?
The region reserved brightness not depend on its intensity but also on its background. All centre square have same intensity. However they appear to the eye to become darker as the background becomes lighter.

24. What is meant by illumination and reflectance?
Illumination is the amount of source light incident on the scene. It is represented as i(x, y).
Reflectance is the amount of light reflected by the object in the scene. It is represented by r(x, y).

26. Define sampling and quantization?
Sampling means digitizing the co-ordinate value (x, y).Quantization means digitizing the amplitude value. Several rods are connected to one nerve end. So it gives the overall picture of the image.This is also known as thin lightvision.

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