Category: Interview Questions

1. How To Find Middle Element Of A Singly Linked List In One Pass?

You should clarify what does mean by one pass in this question. If Interviewer says that you cannot loop twice and you just have to use one loop, then you can use the two pointer approach to solving this problem. In the two pointer approach, you have two pointers, fast and slow. In each step, the fast pointer moves two nodes, while slow pointer just steps one node. So, when fast pointer will point to the last node i.e. where next node is null, the slow pointer will be pointing to the middle node of the linked list.

2. How To Check If Linked List Contains Loop In Java? How To Find The Starting Node Of The Loop?

This is another interesting linked list problem which can be solved using the two pointer approach discussed in the first question. This is also known as tortoise and hare algorithm. Basically, you have two pointers fast and slow and they move with different speed i.e. fast moves 2 notes in each iteration and slow moves one node. If linked list contains cycle then at some point in time, both fast and slow pointer will meet and point to the same node, if this didn’t happen and one of the pointer reaches the end of linked list means linked list doesn’t contain any loop.

3. How To Reverse A Linked List In Java?

This is probably the most popular linked list interview question, which is asked to both junior programmers with 2 to 3 years of experience and senior developers containing 4 to 6 years of experience. Some of you may think this is the simplest of linked list problem but when you actually go doing it, you will be stuck and many places. The simplest approach to solving this problem is by using recursion because linked list is a recursive data structure as shown in the solution article.

4. How To Reverse A Singly Linked List Without Recursion In Java?

The previously linked list interview question becomes even more challenging when the interviewer asked you to solve the problem without recursion. you need to keep reversing links on the node until you reach the end, which will then become new head.

5. How Would You Remove A Node From A Doubly Linked List?

This is one of the frequently asked linked list interview questions, mostly asked freshers and computer science college graduates. In order to remove a node from the doubly linked list, you need to go through that node and then change the links so that it points to the next node. Removing nodes from head and tail is easy in linked list but removing a node from the middle of the linked list requires you to travel to the node hence take O(n) time. If you want to learn more about basic operations on linked list data structure, please read a good book on Data Structure and Algorithms e.g. Introduction to Algorithms by Thomas H. Carmen.

6. Write A Program To Convert A Binary Tree Into A Doubly Linked List?

This problem is opposite of question 25 where you need to write a program to convert a double linked list to the balanced binary tree.  The left and right pointers in nodes of a binary tree will be used as previous and next pointers respectively in converted doubly linked list. The order of nodes in the doubly linked list must be same as Inorder of the given Binary Tree. The first node of Inorder traversal (left most node in the binary tree) must be the head node of the doubly linked list.

7. How To Remove Duplicate Nodes In An Unsorted Linked List?

This problem is similar earlier problems related to String and arrays i.e. removing duplicate elements in an array (see) or removing duplicate characters from given String (see here). You need to write a program to remove all duplicate nodes from an unsorted linked list in Java. For example if the linked list is 22->21->22->31->41->23->21 then your program should convert the list to 22->21->31->41->23. This question is also given in the famous Cracking the Coding Interview book so you can look at their solution as well.

8. How To Find The Length Of A Singly Linked List In Java?

This is one of the easiest linked list questions you can expect in an interview. That’s why it is often asked on telephonic interviews. In order to find the length of linked list, you can iterate over linked list and keep a count of nodes until you reach the end of the linked list where next node will be null. The value of the counter is the length of linked list.

9. Write Code To Print Out The Data Stored In Each Node In A Singly Linked List?

This is another simplest question which just tests whether you know linked list traversal or not. You can get the value from the node by accessing its value property, you just need to traverse through linked list, access each node and print value.

10. Write A Program To Print A Linked List In Reverse Order? E.g. Print Linked List From Tail To Head?

You can print nodes of linked list in reverse order by using Stack data structure in two steps:

Step 1:
Traverse the linked list from the head and put the value of each node into Stack until you reach the last node. This will take O(n) time.

Step 2:
Pop the elements out from the stack and print. This will take O(1) time.

Input:
1->2->3

Output:
3 2 1

11. How To Find The Kith Node From The End In A Singly Linked List?

• This is one of the tricky but frequently asked linked list questions. Some of you may be wondering how do you find kth node from end, singly linked list can only traverse in one direction and that is forward then how do you count nodes from the end.
• Well, you don’t have to, you can still move forward and count nodes from the end? Actually, that’s the trick. You can use two pointers to find the Nth node from the end in a singly linked list. They are known as fast and slow points.
• You start slow pointer when the fast pointer reaches to the Kth node from start e.g. if you have to find 3rdnode from the end then you start slow pointer when the fast pointer reaches to the 3rd node. This way, when your fast pointer reaches to the end, your slow pointer will be on the 3rd node from the end.

12. How To Delete Alternate Nodes Of A Linked List?

You are given a Singly Linked List.  Starting from the second node delete all alternate nodes of it. For example, if the given linked list is 1->4->8->10->15 then your function should convert it to 1->8->15.

13. What Is The Difference Between An Array And Linked List In Java?

This is one of the frequently asked linked list questions on programming job interviews. There is much difference between an array and linked list but the most important is how they are stored into the memory location. Array stores elements at the adjacent memory location, while linked list stores them at scattered, which means searching is easy in an array and difficult in linked list but adding and removing an element from start and end is easy in linked list. See here for more differences between array and linked list.

14. Difference Between Singly And Doubly Linked List In Java?

The key difference between a single and double linked list data structure in java is that singly linked list only contains pointer to next node, which means you can only traverse in one direction i.e. forward, but doubly linked list contains two points, both previous and next nodes, hence you can traverse to both forward and backward direction.

15. How To Implement A Linked List Using Generics In Java?

It’s not easy to implement a linked using generics in Java, especially if have not written any parametric or generic class, but it’s a good exercise to get familiar with both linked list data structure as well generics in Java.

16. How To Insert A Node At The Beginning Of The List?

Inserting a node at the beginning of the list is probably the easiest of all operations. Let’s talk about what is involved here referring to the diagram above. This involves creating a new node (with the new data, say int 10), making its link point to the current first node pointed to by head (data value 2) and lasting changing head to point to this new node. Simple, right.

17. How To Insert A Node At The End Of The List?

This case is a little bit more evolved. If you have a tail pointer, it is as easy as inserting at the beginning of the list. If you do not have a tail pointer, you will have to create the new node, traverse the list till you reach the end (i.e. the next pointer is NULL) and then make that last node’s next pointer point to the new node.

18. How Do You Traverse A Linked List In Java?

There are multiple ways to traverse a linked list in Java e.g. you can use traditional for, while, or do-while loop and go through the linked list until you reach the end of the linked list. Alternatively, you can use enhanced for loop of Java 1.5 or Iterator to traverse through a linked list in Java. From JDK 8 onwards, you can also use java.util.stream.Stream for traversing a linked list.

19. How Do You Find The Sum Of Two Linked List Using Stack In Java?

This is a relatively difficult linked questions when you compare this to reversing a linked list or adding/removing elements from the linked list. In order to calculate the sum of linked list, you calculate the sum of values held at nodes in the same position, for example, you add values at first node on both the linked list to find the first node of resultant linked list. If the length of both linked list is not same then you only add elements from shorter linked list and just copy values for remaining nodes from the long list.

20. How Do You Convert A Sorted Doubly Linked List To A Balanced Binary Search Tree In Java?

This is one of the difficult linked list questions you will find on interviews. You need to write a program to convert a given doubly Linked, which is sorted in ascending order to construct a Balanced Binary Search Tree which has same the values as the given doubly linked list. The challenge is usually increased by putting a restriction to construct the BST in-place i.e. no new node should be allocated for tree conversion)

Input:
A Doubly linked list 10  20 30  40 50  60  70

Output:
A balanced binary search tree BST

         40

      /     

    20      60

   /          /   

 10   30  40   70

21. How Do You Calculate The Sum Of Two Linked List Using Recursion In Java?

This is another interesting linked list based algorithm question for Java programmers. You cannot use the java.util.LinkdList class but you have to write your own linked list implementation in Java to solve this problem.

22. How To Implement Lru Cache In Java Using Linked List?

An LRU cache is the cache where you remove least recently used an element when the cache is full or about to fill. It’s relatively easy in Java if you are allowed to use one of the Collection class e.g. you can use a LinkedHashMap to implement LRU cache in Java, but you should also prepare how you can use a doubly linked list to create an LRU cache.

23. How Do You Reverse Every Alternate K Nodes Of A Linked List In Java?

This is another difficult linked list algorithm question which is mostly asked to experienced programmers e.g. programmer having 3 to 6 years of experience. You have been given a singly linked list and you need to write a function to reverse every alternate k nodes (where k is an input to the function) in an efficient way. You also need to calculate the time and space complexity of your algorithm.

Example:

Inputs:
   1->2->3->4->5->6->7->8->9->NULL and k = 3

Output:
   3->2->1->4->5->6->9->8->7->NULL.

24. How Do Add Two Numbers Represented Using Linked List In Java?

You have given two numbers represented by two linked lists, write a function that returns the sum of these two lists. The sum list is linked list representation of addition of two input numbers. There are two restrictions to solve this problem i.e. you cannot modify the lists and you are not allowed to use explicit extra space. You can use recursion to solve this problem.

Input:

  First List:
1->2->3  // represents number 123

  Second List:
9->9->9 //  represents number 999

Output:

 Resultant list:
1->1->2->2  // represents number 1122

That’s all about some of the frequently asked linked list based coding questions from Programming Interviews. As I said, linked list is one of the essential data structure and you should have a good command over it, especially if you are preparing for Google or Amazon job interview. Once you solve these problems, you can try solving questions given in Algorithm Design Manual by Steven S. Skiena. They are tougher but can really improve your data structure and algorithm skills.

25. What Is A Linked List?

Linked list is an ordered set of data elements, each containing a link to its successor (and typically its predecessor).

26. How Many Pointers Are Required To Implement A Simple Linked List?

You can find generally 3 pointers engaged:

1. A head pointer, pointing to the start of the record.
2. A tail pointer, pointing on the last node of the list. The key property in the last node is that its subsequent pointer points to nothing at all (NULL).
3. A pointer in every node, pointing to the next node element.

27. How Many Types Of Linked Lists Are There?

Singly linked list, doubly linked list, multiply linked list, Circular Linked list.

28. How To Represent A Linked List Node?

The simplest representation of a linked list node is wrapping the data and the link using a typedef structure and giving the structure as a Node pointer that points to the next node. An example representation in C is

/*ll stands for linked list*/

typedef struct ll

{

    int data;

    struct ll *next;

} Node;

29. Describe The Steps To Insert Data At The Starting Of A Singly Linked List?

Inserting data at the beginning of the linked list involves creation of a new node, inserting the new node by assigning the head pointer to the new node next pointer and updating the head pointer to the point the new node. Consider inserting a temp node to the first of list

Node *head;

void InsertNodeAtFront(int data)

{

    /* 1. create the new node*/

    Node *temp = new Node;

    temp->data = data;

    /* 2. insert it at the first position*/

    temp->next = head;

    /* 3. update the head to point to this new node*/

    head = temp;

}

30. How To Insert A Node At The End Of Linked List?

This case is a little bit more complicated. It depends on your implementation. If you have a tail pointer, it’s simple. In case you do not have a tail pointer, you will have to traverse the list till you reach the end (i.e. the next pointer is NULL), then create a new node and make that last node’s next pointer point to the new node.

void InsertNodeAtEnd(int data)

{

   /* 1. create the new node*/

    Node *temp = new Node;

   temp->data = data;

    temp->next = NULL;

    /* check if the list is empty*/

    if (head == NULL)

    {

        head = temp;

        return;

    }

    else

    {

        /* 2. traverse the list till the end */

        Node *traveller = head;

        while (traveler->next != NULL)

            traveler = traveler->next;

       /* 3. update the last node to point to this new node */

        traveler->next = temp;

    }

}

31. How To Insert A Node In Random Location In The List?

As above, you’d initial produce the new node. Currently if the position is one or the list is empty, you’d insert it initially position. Otherwise, you’d traverse the list until either you reach the specified position or the list ends. Then you’d insert this new node. Inserting within the middle is that the difficult case as you have got to make sure you do the pointer assignment within the correct order. First, you’d set the new nodes next pointer to the node before that the new node is being inserted. Then you’d set the node to the position to purpose to the new node. Review the code below to get an idea.

void InsertNode(int data, int position)

{

    /* 1. create the new node */

    Node *temp = new Node;

    temp->data = data;

    temp->next = NULL;

    /* check if the position to insert is first or the list is empty */

    if ((position == 1) || (head == NULL))

    {

        // set the new node to point to head

        // as the list may not be empty

        temp->next = head;

        // point head to the first node now

        head = temp;

        return;

    }

    else

    {

        /* 2. traverse to the desired position */

    Node *t = head;

int currPos = 2;

        while ((currPos < position) && (t->next != NULL))

        {

            t = t->next;

            currPos++;

        }

        /* 3. now we are at the desired location */

        /* 4 first set the pointer for the new node */

        temp->next = t->next;

        /* 5 now set the previous node pointer */

        t->next = temp;

    }

}

32. How To Delete A Node From Linked List?

• The following are the steps to delete node from the list at the specified position.
• Set the head to point to the node that head is pointing to.
• Traverse to the desired position or till the list ends; whichever comes first
• You have to point the previous node to the next node.

33. How To Reverse A Singly Linked List?

• First, set a pointer (*current) to point to the first node i.e. current=head.
• Move ahead until current!=null (till the end)
• set another pointer (*next) to point to the next node i.e. next=current->next
• store reference of *next in a temporary variable (*result) i.e. current->next=result
• swap the result value with current i.e. result=current
• And now swap the current value with next. i.e. current=next
• return result and repeat from step 2
• A linked list can also be reversed using recursion which eliminates the use of a temporary variable.

34. Compare Linked Lists And Dynamic Arrays?

• A dynamic array is a data structure that allocates all elements contiguously in memory, and keeps a count of the present number of elements. If the area reserved for the dynamic array is exceeded, it’s reallocated and traced, a costly operation.
• Linked lists have many benefits over dynamic arrays. Insertion or deletion of an element at a specific point of a list, is a constant-time operation, whereas insertion in a dynamic array at random locations would require moving half the elements on the average, and all the elements in the worst case.
• Whereas one can delete an element from an array in constant time by somehow marking its slot as vacant, this causes fragmentation that impedes the performance of iteration.

35. What Is A Circular Linked List?

In the last node of a singly linear list, the link field often contains a null reference. A less common convention is to make the last node to point to the first node of the list; in this case the list is said to be ‘circular’ or ‘circularly linked’.

36. What Is The Difference Between Singly And Doubly Linked Lists?

A doubly linked list whose nodes contain three fields: an integer value and two links to other nodes one to point to the previous node and other to point to the next node. Whereas a singly linked list contains points only to the next node.

37. What Are The Applications That Use Linked Lists?

Both stacks and queues are often implemented using linked lists, other applications are skip list, binary tree, unrolled linked list, hash table, heap, self-organizing list.

38. How To Remove Loops In A Linked List (or) What Are Fast And Slow Pointers Used For?

The best solution runs in O(N) time and uses O(1) space. This method uses two pointers (one slow pointer and one fast pointer). The slow pointer traverses one node at a time, while the fast pointer traverses twice as fast as the first one. If the linked list has loop in it, eventually the fast and slow pointer will be at the same node. On the other hand, if the list has no loop, obviously the fast pointer will reach the end of list before the slow pointer does. Hence we detect a loop.

39. What Will You Prefer To Use A Singly Or A Doubly Linked Lists For Traversing Through A List Of Elements?

Double-linked lists require more space per node than singly liked lists, and their elementary operations such as insertion, deletion are more expensive; but they are often easier to manipulate because they allow fast and easy sequential access to the list in both directions. On the other hand, doubly linked lists cannot be used as persistent data structures. So, for traversing through a list of node, doubly linked list would be a better choice.

1. What Scales Are Used For Magnitude? For Intensity?

• Seismic scales
• Environmental Seismic Intensity scale (ESI)
• European Macroseismic Scale (EMS)
• Liedu.
• Medvedev–Sponheuer–Karnik (MSK)
• Modified Mercalli (MM)
• PHIVOLCS Earthquake Intensity Scale (PEIS)
• Shindo.

2. How Does The Richter Scale?

The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs.

3. What Is The Difference Between Magnitude And Intensity?

Intensity:
The severity of earthquake shaking is assessed using a descriptive scale – the Modified Mercalli Intensity Scale.

Magnitude:
Earthquake size is a quantitative measure of the size of the earthquake at its source. The Richter Magnitude Scale measures the amount of seismic energy released by an earthquake.

When an earthquake occurs, its magnitude can be given a single numerical value on the Richter Magnitude Scale. However the intensity is variable over the area affected by the earthquake, with high intensities near the epicentre and lower values further away. These are allocated a value depending on the effects of the shaking according to the Modified Mercalli Intensity Scale.

4. What Is The Richter Magnitude Scale?

The Richter magnitude scale (also Richter scale) assigns a magnitude number to quantify the size of an earthquake. The Richter scale, developed in the 1930s, is a base-10 logarithmic scale, which defines magnitude as the logarithm of the ratio of the amplitude of the seismic waves to an arbitrary, minor amplitude.

5. What Is The Magnitude And Intensity Of An Earthquake?

The intensity is a number (written as a Roman numeral) describing the severity of an earthquake in terms of its effects on the earth’s surface and on humans and their structures. Several scales exist, but the ones most commonly used in the United States are the Modified Mercalli scale and the Rossi-Forel scale.

6. What Is The Magnitude Of An Earthquake?

Magnitude is a measure of the amount of energy released during an earthquake. It may be expressed using several magnitude scales. One of these, Used in Southern California, is called the Richter scale.

7. What Are The Costs Of Geophysics?

Cost is, of course, a key consideration. Most Environmental and Engineering Geophysical surveys have a cost structure that is similar to that of any licensed professional: an hourly consulting fee plus equipment rental costs. In addition, there are associated costs of mobilization (since most geophysical surveys require acquisition of data in the field), instrumentation amortization, data processing and interpretation, and report writing and presentation.

Ultimately, the application of geophysics must be assessed in terms of its projected costs and benefits as indicated above. EEGS professionals are trained to advise in developing cost and benefit assessments. It makes no sense to conduct a geophysical survey if the costs are projected to exceed any possible economic gains, or to exceed the project’s operational budget. In general, however, geophysical surveys are almost always substantially less expensive than traditional non-technical means of investigation such as excavation or drilling.

8. How Are Geophysical Methods Applied In Practice?

The implementation of geophysical methods is a structured process that consists of a number of key steps, including:

Initial evaluation of the problem at hand (i.e. what is the suspected problem, what initial information is known about the site, what additional information is required, and what are the desired outcomes)

Determination of which geophysical method (or combination of methods) will yield the optimal results. Not all methods will be applicable as noted in some of the links above, therefore, it is critical to carefully assess which methods are most likely to provide data and information relevant to the problem of interest. Also, while some methods may provide information, they may not be cost-effective in a particular context.

Identification of the scope (or size) of the required geophysical coverage.

Assessment of the way in which the data and information are to be acquired, interpreted and presented so as to address the issue at hand.

After these basic questions have been answered and the project approved, the geophysical work will commence.

Typically, Environmental and Engineering Geophysics consists of field surveys conducted along oriented lines (i.e. survey grids) over the desired area of interest. For more information on field surveying, you may want to refer to the links provided above in the “What Geophysical Field Methods are Available” section.

9. What Geophysical Methods Are Available?

Horizontal loop electromagnetic apparatus is used to locate conductive zones that may be leachate plumes. As noted previously, geophysical methods as applied to Environmental and Engineering Geophysics were derived from other principal areas of subsurface investigation, including petroleum, mineral and groundwater exploration. 

The methods or techniques most commonly employed by practitioners include:

• Electromagnetics.
• Gravity.
• Ground penetrating radar (GPR).
• Magnetics.
• Resistivity (and / or induced polarization).
• Seismic refraction (and / or near surface seismic reflection).
• Spontaneous potential (or “SP”).
• Induced polarization (or “IP”).

10. What Are The Benefits Of Geophysics?

Data from very low frequency electromagnetics have been converted to electrical current density and depth. The dark blue color indicates the core of a leachate plume emanating from a landfill. Environmental and Engineering Geophysics offers a unique window into the earth as a means of detecting sub-surface conditions, and its relevancy lies in the concrete and cost-effective benefits it delivers. These include:

Non-destructive :
 It is ideal for use in populated areas, such as cities, where many of today’s environmental and engineering issues arise. It also means an archeological site can be examined without destroying it in the process.

Efficiency :
 It provides a means of evaluating large areas of the subsurface rapidly.

Comprehensiveness : 
Combinations of methods (i.e. multi-disciplinary methods) provide the means of applying different techniques to solve complex problems. The more physical properties that are evaluated, the less ambiguous the interpretation becomes.

Cost-effective :
 Geophysics does not require excavation or direct access to subsurface (except in the case of borehole methods where access is typically by drilled holes). This means vast volumes of earth can be evaluated at far less cost than excavation or even grid-drilling methods.

Proven : 
The majority of techniques have been in existence for more than a half-century and are mature, yet still relatively undiscovered and underutilized by decision-makers who face complex environmental and engineering problems.

11. What Are The Types Of Problems Addressed?

The sledge hammer provides a source of energy for determination of the depth to water table and bedrock. Generally, environmental and engineering problems fall into the following classes or types:

• Infrastructure (highways and bridges)
• Groundwater (exploration and contaminant mapping)
• Geohazards (earthquake mitigation and collapse structure mapping)
• Urban (utility mapping, underground storage tank location)
• Geologic Mapping
• Archeology
• Forensics (i.e., illegal burials, etc.)
• Civil Engineering / Non-Destructive Testing (NDT)
• So-called “Brownfield” and Landfill Investigations
• Unexploded Ordnance (UXO detection and characterization)
• Dam Safety

12. What Is Geophysics?

The subsurface site characterization of the geology, geological structure, groundwater, contamination, and human artifacts beneath the Earth’s surface, based on the lateral and vertical mapping of physical property variations that are remotely sensed using non-invasive technologies. Many of these technologies are traditionally used for exploration of economic materials such as groundwater, metals, and hydrocarbons.

13. Give A Formula Which Relates Wavelength And Frequency?

The equation that relates wavelength and frequency for electromagnetic waves is: λν=c where λ is the wavelength, ν is the frequency and c is the speed of light.

14. Where Do The Shallow Earthquakes Occur?

Most earthquakes are a result of fault movement in the crust, a relatively thin layer on the Earth’s surface. In Cascadia, most earthquakes are shallow quakes that occur within the crust of the North America plate to a depth of about 20 miles (35 km).

15. What Causes A Deep Focus Earthquake?

A deep-focus earthquake in seismology is an earthquake with a hypocenter depth exceeding 300 km. They occur almost exclusively at oceanic-continental convergent boundaries in association with subducted oceanic lithosphere.

16. What Causes Earthquakes?

Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake. When two blocks of rock or two plates are rubbing against each other, they stick a little.

17. What Is Meant By A Diurnal Cycle?

A diurnal cycle is any pattern that recurs every 24 hours as a result of one full rotation of the Earth with respect to the Sun. In climatology, the diurnal cycle is one of the most basic forms of climate patterns. The most familiar such pattern is the diurnal temperature variation.

18. What Are Diurnal Changes?

Diurnal temperature variation is the variation between a high temperature and a low temperature that occurs during the same day.

19. What Are Magnetic Storms?

A disturbance of the magnetic field of the earth (or other celestial body).

20. What Causes The Earth’s Oblateness?

The Earth’s oblateness, shown here as a bulge at the equator (highly exaggerated to demonstrate the concept) causes a twisting force on satellite orbits that change various orbital elements over time. The force caused by the equatorial bulge is still gravity.

21. Define Declination, Inclination.

Magnetic declination is the angle between magnetic north (the direction the north end of a compass needle points) and true north. The declination is positive when the magnetic north is east of true north. Magnetic inclination is the angle made by a compass needle when the compass is held in a vertical orientation.

22. Define Curie Temperature.

The Curie temperature (TC), or Curie point, is the temperature at which certain materials lose their permanent magnetic properties, to be replaced by induced magnetism.

23. What Is A Tomographic Image?

Tomography refers to imaging by sections or sectioning, through the use of any kind of penetrating wave. The method is used in radiology, archaeology, biology, atmospheric science, geophysics, oceanography, plasma physics, materials science, astrophysics, quantum information, and other sciences.

24. What Part Of The Earth Does Not Receive Direct P Waves From A Quake?

The shadow zone is the area of the earth from angular distances of 104 to 140 degrees from a given earthquake that does not receive any direct P waves. The shadow zone results from S waves being stopped entirely by the liquid core and P waves being bent (refracted) by the liquid core.

25. What Is Seismic Imaging?

Seismic imaging is a tool that bounces sound waves off underground rock structures to reveal possible crude oil– and natural gas–bearing formations. Seismologists use ultrasensitive devices called geophones to record the sound waves as they echo within the earth.

26. What Is A Harmonic Tremor?

A harmonic tremor is a sustained release of seismic and infrasonic energy typically associated with the underground movement of magma, the venting of volcanic gases from magma, or both.

27. What Is Seismic Tomography?

Seismic tomography is a technique for imaging the subsurface of the Earth with seismic waves produced by earthquakes or explosions. P-, S-, and surface waves can be used for tomographic models of different resolutions based on seismic wavelength, wave source distance, and the seismograph array coverage.

28. What Are Sv And Sh Waves?

S-waves polarized in the horizontal plane are classified as SH-waves. If polarized in the vertical plane, they are classified as SV-waves. When an S- or P-wave strikes an interface at an angle other than 90 degrees, a phenomenon known as mode conversion occurs.

29. What Is A Seismograph And How Does It Function?

A seismograph is the device that scientists use to measure earthquakes. The goal of a seismograph is to accurately record the motion of the ground during a quake.

30. How Does A Seismograph Works?

Seismographs can detect quakes that are too small for humans to feel. During an earthquake, ground-shaking seismic waves radiate outward from the quake source, called the epicenter. Different types of seismic waves travel at different speeds and through different parts of the Earth during a quake.

31. Distinguish Between A Seismograph And A Seismogram?

A seismogram is a visual record that is created by a seismograph. A seismograph is a piece of equipment that records earthquake movements. These two items go hand in hand and are essential for the study of earthquakes.

1. What Is A Portlet? Explain Its Capabilities.

Portlets are UI components that are pluggable and are managed, displayed in a web portal. Markup code fragments are produced by the portlets which are aggregated into a portal page.

A portlet resembles an application that is web based and is hosted in a portal. Email, discussion forums, news, blogs, weather reports are some of the examples of portlets.

2. What Is Horizontal Portals?

These are the portals are of type general interest. Yahoo!,Lycos,AOL,Freeserve,Sympatico are examples of horizontal portals.

3. Explain The Concepts And Capabilities Of Portal Structure Markup Language, Psml?

PSML was created to allow abstraction and content structure within Jetspeed. It has two markups:

1. Registry markup
   : Describes the availability of resources to the Jetspeed engine. It supports multiple portlet registries.
2. Site markup
   : The availability of portlets are described by this markup, which is displayed for a given user.

4. Explain Portal Architecture?

The core implementation of the portal is UI, hosted by a Portal server. The HTTP requests, HTML responses, and returning appropriate portal pages are handled by the Portal UI. Enterprise Web application also can be handled by the Portal Server.

The portal architecture has the following:

• Automaton Server:
  This server performs the management of job scheduling and implementation of a portal. It accesses all remote crawlers and profile services retrieved and stored from a remote database.
• Image Server:
  This server hosts images and other web page content used by web services and a portal. With this configuration, large static files are to be sent directly to the browser without portal server impacts.
• Search Server:
  This server indexes and searches all the information, applications, communities, documents, web sites through portal.
• Collaboration Server:
  Web content publication and management for portals and web applications are supported by this server. Its functionality can be accessed by a remote web services through Enterprise Web Development kit.
• Content Server:
  Publication and management of web content for portals and web applications along with form based publishing, branding, templates, content expiration is allowed by this server.
• Authentication Server:
  This server handles the portal authentication for users and remote services can be accessed through EDK.
• Remote Servers:
  Web services written using the EDK are hosted by remote servers. The servers can be in different countries, on different platforms and domains.

5. What Is Vertical Portals?

They provide a gateway to the information pertaining to a specific industry such as insurance, banking, finance, automobile, telecom etc.

6. What Are Jboss Portal Server Features?

• Highly integrated web applications’ costs reduce by portals. JBoss enables the reusability of branding and deploying new applications of composite nature.
• The users and the industry can be customized, personalized their experiences in a secure and well governed manner by using JBoss portal.
• JBoss incorporate components into a portal as reusable and standardized portlets, as Jboss is platform independent.
• Performance and scalability is ensured.

7. What Is Content Server In Portal Architecture?

Publication and management of web content for portals and web applications along with form based publishing, branding, templates, content expiration is allowed by this server.

8. What Is Portletsession Interface?

User identification across many requests and transient information storage about the user is processed by PortletSession interace. One PortletSession is created per portlet application per client.

The PortletSession interface provides a way to identify a user across more than one request and to store transient information about that user.

The storing of information is defined in two scopes- APPLICATION_SCOPE and PORTLET_SCOPE.

APPLICATION_SCOPE: All the objects in the session are available to all portlets,servlets, JSPs of the same portlet application, by using APPLICATION_SCOPE.

PORTLET_SCOPE: All the objects in the session are available to the portlet during the requests for the same portlet window. The attributes persisted in the PORTLET_SCOPE are not protected from other web components.

9. What Is B2b Portals?

The enterprises extend to suppliers and partners by using B2B portals.

10. Explain About B2e Portals?

The enterprise knowledge base integration and related applications into user customizable environment is done with B2E portals. This environment is like one stop shop.

11. What Is Collaboration Server In Portal Architecture?

Web content publication and management for portals and web applications are supported by this server. Its functionality can be accessed by a remote web services through Enterprise Web Development kit.

12. What Is Portletcontext Interface?

The portlet view of the portlet container is defined by PortletContext. It allows the availability of resources to the portlet. Using this context, the portlet log can be accessed and URL references to resources can be obtained. There is always only one context per portlet application per JVM.

13. What Is B2e Portals?

The enterprise knowledge base integration and related applications into user customizable environment is done with B2E portals. This environment is like one stop shop.

14. Why Portals?

The following are the reasons to use portals:

• Unified way of presenting information from diverse sources.
• Services like email, news, infotainment, stock prices and other features are offered by portals.
• Provides consistent look and feel for enterprise. Eg. MSN, Google sites.

15. What Is Search Server In Portal Architecture?

This server indexes and searches all the information, applications, communities, documents, web sites through portal.

16. Explain The Types Of Portals, Function-based Portals And User-based Portals?

Function-based portals

• Horizontal Portals: 
  These are the portals are of type general interest. Yahoo!,Lycos,AOL,Freeserve,Sympatico are examples of horizontal portals.
• Vertical Portals: 
  They provide a gateway to the information pertaining to a specific industry such as insurance, banking, finance, automobile, telecom etc.

User-Based Portals

• B2B Portals : 
  The enterprises extend to suppliers and partners by using B2B portals.
• B2C Portals : 
  The enterprises extend to customers for ordering, billing, services by using B2C portals.
• B2E Portals : 
  The enterprise knowledge base integration and related applications into user customizable environment is done with B2E portals. This environment is like one stop shop.

17. What Is B2c Portals?

The enterprises extend to customers for ordering, billing, services by using B2C portals.

18. What Is Image Server In Portal Architecture?

This server hosts images and other web page content used by web services and a portal. With this configuration, large static files are to be sent directly to the browser without portal server impacts.

19. Do You Know What Is Portletcontext Interface?

The portlet view of the portlet container is defined by PortletContext. It allows the availability of resources to the portlet. Using this context, the portlet log can be accessed and URL references to resources can be obtained. There is always only one context per portlet application per JVM.

20. What Is Automaton Server In Portal Architecture?

This server performs the management of job scheduling and implementation of a portal. It accesses all remote crawlers and profile services retrieved and stored from a remote database.

21. What Is The Concepts And Capabilities Of Portal Structure Markup Language, Psml?

PSML was created to allow abstraction and content structure within Jetspeed.

It has two markups:

• Registry markup: Describes the availability of resources to the Jetspeed engine. It supports multiple portlet registries.
• Site markup: The availability of portlets are described by this markup, which is displayed for a given user.

22. Can You Explain Why We Use Portals?

The following are the reasons to use portals:

• Unified way of presenting information from diverse sources.
• Services like email, news, infotainment, stock prices and other features are offered by portals.
• Provides consistent look and feel for enterprise. Eg. MSN, Google sites.

1. Define Perl Scripting?

In the IT market, Perl scripting is considered as a robust scripting language which is used in various fields. Perl is good at obtaining Regular expressions and in all the fields of application it is unique. Perl is a scripting language which is based on interpreter but not on the languages based on compiler. In all the applications, optimization is used.

2. Why To Use Perl Scripting?

Perl scripting is mainly used in functional concepts as well as regular expressions, you can also design own policies to obtain generalized pattern using regular expression. Perl is compatible or supports more than 76 operating systems and 3000 modules and it is known as Comprehensive Perl Archive Network modules.

3. What Is Perl?

Perl is a programming language which is based on shell, C, Lisp, etc. In general, Perl is mainly used for network operations, OS program and for developing some websites.

4. Why To Use Perl?

• It is a powerful interpreter for free.
• Perl is flexible and portable. It is very easy to learn Perl language.

5. Why Do You Create An Application For Real Time System In Which Processing Speed Is Vital?

Perl is used in the following cases:
• To process large text
• When data manipulation is done by application
• If you require fast developments expand to become libraries
• To load database operations

6. Which Is Your Favorite Module And Why It Is?

CGI.pm is my favorite module and it handles several tasks such as printing the headers, parsing the form input and it handles sessions and cookies effectively.

7. How Perl Warnings Are Turn On And Why Is It Important?

In general, Perl excuse strange and also wrong code sometimes. Thus, the time spent for searching weird results and bugs in very high. You can identify common mistakes and strange places in the code easily when warnings are turned on. In the long run, the time required for debugging is saved a lot. There are numerous ways to turn on the warnings of Perl:

• -w option is used on the command line for Perl one-liner
• -w option on shebang line is used on windows or UNIX. Windows Perl interpreter do not require it.
• For other systems, compiler documentation is checked or compiler warnings are selected.

8. Differentiate Use And Require?

Use:

• This method is used for modules.
• The objects which are included are varied at compilation time.
• You need not give a file extension.

Require:

• This method is used for both modules and libraries.
• The objects are included are verified at run time.
• You need not give file extension.

9. Distinguish My And Local?

The variables which are declared using “my” lives only in that particular block ion which they are declared and inherited functions do not have a visibility that are called in that block. The variables which are defined as “local” are visible in that block and they have a visibility in functions which are called in that particular block.

10. Why Perl Patterns Are Not Regular Expressions?

Perl patterns have back references
By the definition, a regular expression should determine next state infinite automation without extra money to keep in previous state. State machine is required by the pattern / ([ab] +) c1/ to remember old states. Such patterns are disqualified as being regular expressions in the term’s classic sense.

11. What Happens If A Reference Is Returned To Private Variable?

Your variables are kept on track by the Perl, whether dynamic or else, and does not free things before you use them.

12. Define Scalar Data And Variables?

The concept of data types is flexible, which is present in Perl. Scalar is a single thing such as a string or a number. The java concepts such as int, float, string, and double are similar to scalar concept of Perl. Strings and numbers are exchangeable. Scalar variable is nothing but a Perl variable which is used to store scalar data. A dollar sign $ is used by it which is followed by underscores or alphanumeric characters. It is a case sensitive.

13. Why -w Argument Is Used With Perl Programs?

-w option of the interpreter is used by most of the Perl developers especially in the development stage of an application. It is warning option to turn on multiple warning messages that are useful in understanding and debugging the application.

14. Which Has Highest Precedence In Between List And Terms? Explain?

In Perl, the highest precedence is for Perl. Quotes, variables, expressions in parenthesis are included in the Terms. The same level of precedence as Terms is for List operators. Especially, these operators have strong left word precedence.

15. Define A Short Circuit Operator?

The C-style operator ll carries out logical operation which is used to tie logical clauses, overall value of true is returned if either clause is true. This operator is known as short-circuit operator because you need not check or evaluate right operand if the left operand is true.

16. In Perl, Name Different Forms Of Goto And Explain?

In Perl, there are three different forms for goto, they are:
• goto name
• goto label
• goto expr
goto name is used along with subroutines, it is used only when it is required as it creates destruction in programs. It is the second form of label where Execution is transferred to a statement labeled LABEL using goto LABEL. The last label form is goto EXPR which expects EXPR to evaluate label.

17. Can You Add Two Arrays Together?

Yes, it is possible to add two arrays together with a push function. A value or values to end of the array is added using push function. The values of list are pushed on to the end of an array using push function. Length of list is used to increase length of an array.

18. How Shift Command Is Used?

The first value of an array shifted using shift array function and it is returned, which results in array shortening by one element and moves everything from a place to left. If an array is not specified to shift, shift uses @ ARGV, the command line arguments of an array is passed to script or to an array named @.

19. Explain Different Types Of Eval Statements?

In general, there are two types of eval statements they are:
• Eval BLOCK and
• Eval EXPR
An expression is executed by eval EXPR and BLOCK is executed by eval BLOCK. Entire block is executed by eval block, BLOCK. When you want your code passed in expression then first one is used and to parse code in the block, second one is used.

20. Describe Returning Values From Subroutines?

The value of last expression which is evaluated is the return value of subroutine or explicitly, a returned statement can be used to exit subroutine which specifies return value. This return value is evaluated in perfect content based on content of subroutine call.

21. What Are The Two Different Types Of Data Perl Handles?

Perl handles two types of data they are
(i) Scalar Variables and
(ii) Lists
Scalar variables hold a single data item whereas lists hold multiple data items.

22. What Are Scalar Variables?

Scalar variables are what many programming languages refer to as simple variables. They hold a single data item, a number, a string, or a perl reference. Scalars are called scalars to differentiate them from constructs that can hold more than one item, like arrays.

23. Explain About Lists?

A list is a construct that associates data elements together and you can specify a list by enclosing those elements in parenthesis and separating them with commas. They could themselves be arrays, hashes or even other lists. Lists do not have a specific list data type.

24. Name All The Prefix Dereferencer In Perl?

The symbol that starts all scalar variables is called a prefix dereferencer. The different types of dereferencer are.
(i) $-Scalar variables
(ii) %-Hash variables
(iii) @-arrays
(iv) &-subroutines
(v) Type globs-*myvar stands for @myvar, %myvar.

25. Explain About An Ivalue?

An ivalue is an item that can serve as the target of an assignment. The term I value originally meant a “left value”, which is to say a value that appears on the left. An ivalue usually represents a data space in memory and you can store data using the ivalues name. Any variable can serve as an ivalue.

26. How Does A “grep” Function Perform?

Grep returns the number of lines the expression is true. Grep returns a sub list of a list for which a specific criterion is true. This function often involves pattern matching. It modifies the elements in the original list.

27. Explain About Typeglobs?

Type globs are another integral type in perl. A typeglob`s prefix derefrencer is *, which is also the wild card character because you can use typeglobs to create an alias for all types associated with a particular name. All kinds of manipulations are possible with typeglobs.

28. Is There Any Way To Add Two Arrays Together?

Of course you can add two arrays together by using push function. The push function adds a value or values to the end of an array. The push function pushes the values of list onto the end of the array. Length of an array can be increased by the length of list.

29. How To Use The Command Shift?

Shift array function shifts off the first value of the array and returns it, thereby shortening the array by one element and moving everything from one place to the left. If you don’t specify an array to shift, shift uses @ ARGV, the array of command line arguments passed to the script or the array named @-.

30. What Exactly Is Grooving And Shortening Of The Array?

You can change the number of elements in an array simply by changing the value of the last index of/in the array $#array. In fact, if you simply refer to a nonexistent element in an array perl extends the array as needed, creating new elements. It also includes new elements in its array.

31. What Are The Three Ways To Empty An Array?

The three different ways to empty an array are as follows
1) You can empty an array by setting its length to a negative number.
2) Another way of empting an array is to assign the null list ().
3) Try to clear an array by setting it to undef, but be aware when you set to undef.

32. How Do You Work With Array Slices?

An array slice is a section of an array that acts like a list, and you indicate what elements to put into the slice by using multiple array indexes in square brackets. By specifying the range operator you can also specify a slice.

33. What Is Meant By Splicing Arrays Explain In Context Of List And Scalar.

Splicing an array means adding elements from a list to that array, possibly replacing elements now in the array. In list context, the splice function returns the elements removed from the array. In scalar context, the splice function returns the last element removed.

34. What Are The Different Types Of Perl Operators?

There are four different types of perl operators they are
(i) Unary operator like the not operator
(ii) Binary operator like the addition operator
(iii) Tertiary operator like the conditional operator
(iv) List operator like the print operator

35. Which Has The Highest Precedence, List Or Terms? Explain?

Terms have the highest precedence in perl. Terms include variables, quotes, expressions in parenthesis etc. List operators have the same level of precedence as terms. Specifically, these operators have very strong left word precedence.

36. What Is Perl Scripting?

Perl Scripting is one of the robust scripting languages in the IT market which is being used in “n” of fields. Perl is rich in finding Regular expressions and stands unique in all fields of application.

PERL is a scripting language. Since all scripting languages are interpreter based languages but not compiler based languages, we use for optimization of code in all application.

37. Why Do We Use Perl Scripting?

We use PERL scripting because it is rich in all regular expressions and functional concepts, we can create our own rules to find out particular generalized pattern by using regular expression. PERL supports or compatible in almost 76+ Operating systems and supports more than 3000 modules, called as CPAN (Comprehensive Perl Archive Network) modules.

38. What Is A Subroutine?

Subroutine is perl is a block of code specially combined/grouped to perform a particular task.Which can be called at any point of time in a perl program.
Advantage using Subroutine
a) helps in modular programming making it easier to understand and maintain.
b)eliminates duplication by reusing the same code/calling the subroutine.

39. Name An Instance You Used In Cpan Module?

CGI, DBI etc are very common packages used from CPAN. there are thousands of other useful modules.

40. I Have A Variable Named $objref Which Is Defined In Main Package. I Want To Make It As A Object Of Class Xyz. How Could I Do It?

use XYZ;
my $objref= XYZ->new();

41. What Is Meant ‘die’ In A Perl Program?

If the condition defined before the DIE statement is NOT met, the script will stop execution at that point, printing out the default error, if a custom error message is not defined.

42. What Is Hash In Perl?

Hash in basically used to comment the script line.
A hash is and unordered set of key/value pairs that you access using strings (keys) as subscripts, to look up the scalar value corresponding to a given key.

43. What Does This Mean :
‘$_’ ?

Default variable in Perl.
Its an Default variable in Perl, where the input from the user will be taken into this variable if the variable is not defined by the user.

44. What Is A Datahash(). What Does It Mean? And For What Purpose It Is Used??

In Win32::ODBC, DataHash() function is used to get the data fetched through the sql statement in a hash format.

45. Explain About Returning Values From Subroutines (functions)?

The return value of the subroutine is the value of the last expression evaluated or you can explicitly use a return statement to exit the subroutine specifying the return value. That return value is evaluated in the appropriate content depending on the content of the subroutine call.

46. What Is Meant By A ‘pack’ In Perl?

• Pack Converts a list into a binary representation
• Takes an array or list of values and packs it into a binary structure, returning the string containing the structure
• Hope that kills the problem

47. How Do You Connect To Database In Perl

There is DBI module. use DBI;my $dbh = DBI->connect(‘dbi:Oracle:orcl’, ‘username’, ‘password’,)where username and password is yours. This is example for oracle database.

For Sybase:
use DBI;
my $dbh = DBI->connect(‘dbi:Sybase:server=$SERVER’, ‘username’, ‘password’)

48. What Is A Short Circuit Operator?

The C-Style operator, ll, performs a logical (or) operation and you can use it to tie logical clauses together, returning an overall value of true if either clause is true. This operator is called a short-circuit operator because if the left operand is true the right operand is not checked or evaluated.

49. How To Connect With Sqlserver From Perl And How To Display Database Table Info?

There is a module in perl named DBI – Database independent interface which will be used to connect to any database by using same code. Along with DBI we should use database specific module here it is SQL server. for MSaccess it is DBD::ODBC, for MySQL it is DBD::mysql driver, for integrating oracle with perl use DBD::oracle driver is used. IIy for SQL server there are available many custom defined ppm( perl package manager) like Win32::ODBC, mssql::oleDB etc.so, together with DBI, mssql::oleDB we can access SQL server database from perl. The commands to access database is same for any database.

50. What Value Is Returned By A Lone Return; Statement?

The undefined value in scalar context, and the empty list value () in list context. This way functions that wish to return failure can just use a simple return without worrying about the context in which they were called.

51. How To Turn On Perl Warnings? Why Is That Important?

Perl is very forgiving of strange and sometimes wrong code, which can mean hours spent searching for bugs and weird results. Turning on warnings helps uncover common mistakes and strange places and save a lot of debugging time in the long run. There are various ways of turning on Perlwarnings:

* For Perl one-liner, use -w option on the command line.
* On Unix or Windows, use the -w option in the shebang line (The first # line in the script). Note: Windows Perl interpreter may not require it.
* For other systems, choose compiler warnings, or check compiler documentation.

52. Write A Script To Reverse A String Without Using Perl’s Built In Functions?

my $txt = ‘Hello World’;
my $len= length($txt);
my $rev;
while($len > 0){
$len–;
$rev .= substr($txt,$len,1);
}
print $txt, ‘ – Reversed = ‘ , $rev;

53. What Is Perl One-liner?

There are two ways a Perl script can be run:
–from a command line, called one-liner, that means you type and execute immediately on the command line. You’ll need the -e option to start like “C: %gt perl -e “print “Hello”;”. One-liner doesn’t mean one Perl statement. One-liner may contain many statements in one line.
–from a script file, called Perl program.

54. What Are The Different Types Of Eval Statements?

There are two different types of eval statements they are eval EXPR and eval BLOCK.
Eval EXPR executes an expression and eval BLOCK executes BLOCK. Eval Block executes an entire block, BLOCK. First one is used when you want your code passed in the expression and the second one is used to parse the code in the block.

55. What Is Your Experience Of Interfacing Perl To Database?

The correct answer is DBI

56. What Is Cpan ? What Are The Modules Coming Under This?

CPAN is Comprehensive Perl Archive Network. It’s a repository contains thousands of Perl modules, source and documentation, and all under GNU/GPL or similar license. Some Linux distributions provide a tool named “cpan” with which you can install packages directly from CPAN

57. Given A File, Count The Word Occurrence (case Insensitive)?

open(FILE,”filename”);
@array=; $wor=”word to be found”;
$count=0; foreach $line (@array) { @arr=split (/s+/,$line);
foreach $word (@arr) { if ($word =~ /s*$wors*/i) $count=$count+1; } }

print “The word occurs $count times”;

58. How Do I Set Environment Variables In Perl Programs?

As you may remember, “%ENV” is a special hash in Perl that contains the value of all your environment variables.

Because %ENV is a hash, you can set environment variables just as you’d set the value of any Perl hash variable. Here’s how you can set your PATH variable to make sure the following four directories are in your path::

$ENV{‘PATH’} = ‘/bin:/usr/bin:/usr/local/bin:/home/yourname/bin’;

59. Why We Use Perl?

1.Perl is a powerful free interpreter.
2.Perl is portable, flexible and easy to learn.

-For shell scripting
-For CGI
-Tons of scripts are available.
-Easy development
-Enormous big support script archive like CPAN
-No one starts to write a Perl scripts from scratch, you choose one from an archive and modify that.
-It is a “mature” scripting language.
-You may find Perl interpreter on every mission critical environment
-Easy to learn

60. Why Does Perl Not Have Overloaded Functions?

Because you can inspect the argument count, return context, and object types all by yourself.
In Perl, the number of arguments is trivially available to a function via the scalar sense of @_, the return context via want array(), and the types of the arguments via ref() if they’re references and simple pattern matching like /^d+$/ otherwise. In languages like C++ where you can’t do this, you simply must resort to overloading of functions.

61. Which Of These Is A Difference Between C++ And Perl?

Perl can have objects whose data cannot be accessed outside its class, but C++ cannot.
Perl can use closures with unreachable private data as objects, and C++ doesn’t support closures. Furthermore, C++ does support pointer arithmetic via `int *ip = (int*)&object’, allowing you do look all over the object. Perl doesn’t have pointer arithmetic. It also doesn’t allow `#define private public’ to change access rights to foreign objects. On the other hand, once you start poking around in /dev/mem, no one is safe.

62. How To Concatenate Strings With Perl?

Method #1 – using Perl’s dot operator:
$name = ‘checkbook’;
$filename = “/tmp/” . $name . “.tmp”;

Method #2 – using Perl’s join function
$name = “checkbook”;
$filename = join “”, “/tmp/”, $name, “.tmp”;

Method #3 – usual way of concatenating strings
$filename = “/tmp/${name}.tmp”;

63. What Is The Difference Between Chop & Chomp Functions In Perl?

chop is used to remove last character,chomp function removes only line endings.

64. What Is Hash?

Hash is an associative array where data is stored in
“key”->”value” pairs.
Eg : fruits is a hash having their names and price
%fruits = (“Apple”, “60”, “Banana”, “20”, “Peers”, “40”);

65. How Would You Replace A Char In String And How Do You Store The Number Of
Replacements?

$str=’Hello’;
$cnt= ($str=~s/l/i/g);
print $cnt;

66. How Do You Open A File For Writing?

open FILEHANDLE, “>$FILENAME”

67. What’s Your Favorite Module And Why?

My Favourite module is CGI.pm Bcoz it can handle almost all the tasks like
1. parsing the form input
2. printiing the headers
3. can handle cookies and sessions and much more

68. How To Implement Stack In Perl?

Stack is LIFO (Last in First out), In perl that could be inplemented using the push() and shift() functions. push() adds the element at the last of array and shift() removes from the beginning of an array.

69. Why Do You Program In Perl?

Perl is easy, fast and its fun to code in perl.
Perl is rich with various packages, N/w programming is very easy and there are lot more advantages to say.

70. How We Can Navigate The Xml Documents?

You can use SAX if what you require is simple accesing of the xml structure. You can go for DOM if you need node handling capabilities like inserting a node, modifying a node, deleteing node and stuff like that.

71. Help In Perl?

perldoc -f print

72. What Is The Use Of “stderr()”?

STDERR:
The special filehandle for standard error in any package.

73. Advantages Of C Over Perl?

In reality PERL interpreter is written in C. So what all advantages C have are also possesed by PERL. Otherwise C is faster than PERL, because PERL is an interpreted language.

74. Perl Regular Expressions Are Greedy” What Does This Mean?

Perl regular expressions normally match the longest string possible. that is what is called as “greedy match”

75. What Does The Word ‘&myvariable’ Mean?
What Does The Symbol ‘&’ Means? What’s Purpose Of It?

&myvariable is calling a sub-routine.

& is used to identify a sub-routine.

76. What Is Super?

Super refers to current package ancestor.

77. What Is Rpc? Why Do I Need It?

RPC:A call to a procedure in a different address space. In a traditional procedure call, the calling procedure and the called procedure are in the same address space on one machine. In a remote procedure call, the calling procedure invokes a procedure in a different address space and usually on a different machine.

78. What Does Init 5 And Init 0 Do?

init 5 will shutdown and Power-off the server.

init 0 will bring the server to the ok> prompt (Fourth monitor)

79. What Does Ndd Do?

ndd command will hardcore the speed of the network interface card.

80. What Is Obp And How Do You Access It?

OBP is called as Open Boot PROM. This OBP can be accessiable thru ok> prompt

81. How Do You Boot From Cd-rom?

Booting form CD-ROM can be done by the command
ok >boot cdrom

82. What Is /etc/system For?

/etc/system is a kernal file of Solaris OS.

83. How Do You Boot From A Network With Jumpstart?

boot net – install

84. What Is Jumpstart?

The Jumpstart feature is an automatic installation process available in the Solaris operating environment. It allows system administrators to categorize machines on their network and automatically install systems based on the category to which a system belongs.

85. What Is Lom

Short for LAN on motherboard. The term refers to a chip or chipset capable of network connections that has been embedded directly on the motherboard of a desktop, workstation or server. Instead of requiring a separate network interface card to access a local-area network, such as Ethernet, the circuits are attached to the motherboard. An advantage of a LOM system is an extra available PCI slot that is not being used by the network adapter.

86. How To Create A Package?

pkgmk -o -r / -d /tmp -f Prototype

87. How Do You View Shared Memory Statistics?

swap -l -> displays swap usage
prstat -> examines all active processes on the system and reports statistics based
on the selected output mode and sort order
vmstat -> reports information about processes, memory, paging, block IO, traps,
and cpu activity
pmap -> lists the virtual memory mappings underlying the given process

88. What Is Vts?

Sun Validation Test Suite -> tests and validates Sun hardware by verifying the configuration and functionality of hardware controllers, devices

89. What Is Grep Used For In Perl?

Grep is used with regular expression to check if a parituclar value exist in an array. it returns 0 if the value does not exists, 1 otherwise.

90. How To Code In Perl To Implement The Tail Function In Unix?

You have to maintain a structure to store the line number and the size of the file at that time eg. 1-10bytes, 2-18bytes.. you have a counter to increase the number of lines to find out the number of lines in the file. once you are through the file, you will know the size of the file at any nth line, use ‘sysseek’ to move the file pointer back to that position (last 10) and then start reading till the end.

91. What Are The Arguements We Normally Use For Perl Interpreter

-e for Execute, -c to compile, -d to call the debugger on the file specified, -T for traint mode for security/input checking -W for show all warning mode (or -w to show less warning)

92. What Is It Meants By ‘$_’?

it is a default variable which holds automatically, a list of arguements passed to the subroutine within parenthesis.

93. What Is The Tk Module?

it provides a GUI interface.

94. How To Concatinate Strings In Perl?

through . operator

95. What Value Is Returned By A Lone ‘return;’ Statement?

The undefined value in scalar context, and the empty list value () in list context. This way functions that wish to return failure can just use a simple return without worrying about the context in which they were called.

96. How Do Find The Length Of An Array?

$@array

97. What Does Read() Return At End Of File?

A defined (but false) 0 value is the proper indication of the end of file for read() and sysread().

98. How Do You Print Out The Next Line From A Filehandle With All Its Bytes Reversed?

print scalar reverse scalar Surprisingly enough, you have to put both the reverse and the into scalar context separately for this to work.

99. What Does Perl Do If You Try To Exploit The Execve(2) Race Involving Setuid Scripts?

Sends mail to root and exits. It has been said that all programs advance to the point of being able to automatically read mail. While not quite at that point (well, without having a module loaded), Perl does at least automatically send it.

100. What Are Scalar Data And Scalar Variables?

Perl has a flexible concept of data types. Scalar means a single thing, like a number or string. So the Java concept of int, float, double and string equals to Perl’s scalar in concept and the numbers and strings are exchangeable. Scalar variable is a Perl variable that is used to store scalar data. It uses a dollar sign $ and followed by one or more aphanumeric characters or underscores. It is case sensitive.

101. How To Start Perl In Interactive Mode?

perl -e -d 1 PerlConsole.

102. What Package You Use To Create A Windows Services?

use Win32::OLE.

103. What Is A Datahash()

in Win32::ODBC, DataHash() function is used to get the data fetched through the sql statement in a hash format.

104. What Does This Symbol Mean ‘->’?

In Perl it is an infix dereference operator. for array subscript, or a hash key, or a subroutine, then this must be a reference. can also be used as method invocation.

105. What Is Cpan?

CPAN is comprehensive Perl Archive Network. its a repository contains thousands of Perl Modules, source and documentation, and all under GNU/GPL or smilar licence. Some linux distribution provide a till names ‘cpan’; which you can install packages directly from cpan.

106. What Is The Difference Between Exec And System?

exec runs the given process, switches to its name and never returns while system forks off the given process, waits for its to complete and then return.

107. What Is The Difference Between For And Foreach?

functionally, there is no difference between them.

108. What Is A Regular Expression?

it defines a pattern for a search to match.

109. What Is Stderr() In Perl?

special file handler to standard error in any package.

110. List The Files In Current Directory Sorted By Size ?

– ls -l | grep ^- | sort -nr

1. What Do You Understand By The Term ‘functional Testing’?

A black box testing technique, where the functionality of an application is tested to generate the desired output by providing certain input is called ‘Functional testing’.

The role of functional testing is not only to validate the behavior of the application as per the requirement document specification but is also to verify whether the application is ready to be released into the live environment or not.

Given below are few functional testing techniques that are commonly used:

• Unit testing
• Smoke testing
• Integration testing
• System Testing
• Usability testing
• Regression testing
• User Acceptance testing

2. What Are The Important Steps That Are Covered In Functional Testing?

Following are the steps that should be covered as a part of functional testing:

• Understanding the Requirement document specification and clearing the doubts and queries in the form of review comments.
• Writing the test cases with respect to the requirement specification by keeping in mind all the scenarios that should be considered for all the cases.
• Identifying the test inputs and requesting the test data that is required to execute the test cases as well as to check the functionality of the application.
• Determine the actual outcomes as per the input values to be tested.
• Execute the test cases that determine whether application behavior is as expected or any defect has occurred.
• Compare the actual result and the computed result to find out the actual outcome.

3. Enlist Some Bug Status Along With Its Description?

Enlisted below are few bug statuses along with their descriptions:

• New:
  When the defect or bug is logged for the first time it is said as New.
• Assigned:
  After the tester has logged a bug, his bug is being reviewed by the tester lead and then it is assigned to the corresponding developer team.
• Open:
  Tester logs a bug in the Open state and it remains in the open state until the developer has performed some task on that bug.
• Resolved/Fixed:
  When a developer has resolved the bug, i.e. now the application is producing the desired output for a particular issue, then the developer changes its status to resolved/fixed.
• Verified/Closed:
  When a developer has changed the status to resolved/fixed then the tester now tests the issue at its end and if it’s fixed then he changes the status of the bug to ‘Verified/Close’.
• Reopen:
  If a tester is able to reproduce the bug again i.e. the bug still exists even after fixing by the developer, it’s status is marked as reopen.
• Not a bug/Invalid:
  A bug can be marked as invalid or not a bug by the developer when the reported issue is as per the functionality but is logged due to misinterpretation.
• Deferred:
  Usually when the bug is of minimal priority for the release and if there is lack of time, in that case, those minimal priority bugs are deferred to the next release.
• Cannot Reproduce:
  If the developer is unable to reproduce the bug at its end by following the steps as mentioned in the issue.

4. What Is Known As Data-driven Testing?

Data-driven testing is the methodology where a series of test script containing test cases are executed repeatedly using data sources like Excel spreadsheet, XML file, CSV file, SQL database for input values and the actual output is compared to the expected one in the verification process.

For Example:
Test studio is used for data-driven testing.

Some advantages of data-driven testing are:

• Reusability.
• Repeatability.
• Test data separation from test logic.
• The number of test cases is reduced.

5. What Is Automation Testing?

Automation testing is a testing methodology where automation tool is used to execute the test cases suite in order to increase test coverage as well speed to test execution. Automation testing does not require any human intervention as it executes pre-scripted tests and is capable of reporting and comparing outcomes with previous test runs.

Repeatability, ease of use, accuracy, and greater consistency are some of the advantages of Automation testing.

Some automation testing tools are listed below:

• Selenium
• Tellurium
• Watir
• SoapUI

6. Explain The Term Stress Testing And Load Testing?

Stress Testing is a form of performance testing where the application is bound to go through exertion or stress i.e. execution of application above the threshold of the break to determine the point where the application crashes. This condition usually arises when there are too many users and too much of data.

Stress testing also verifies the application recovery when the work load is reduced.

Load Testing is a form of performance testing where the application is executed above various load levels to monitor peak performance of the server, response time, server throughput, etc. Through load testing process stability, performance and integrity of the application are determined under concurrent system load.

7. What Do You Understand By Volume Testing?

Volume testing is a form of performance testing which determines the performance levels of the server throughput and response time when concurrent users, as well as large data load from the database, are put onto the system/application under tests.

8. What Do You Understand By Exploratory Testing? When Is It Performed?

Exploratory testing means testing or exploring the application without following any schedules or procedures. While performing exploratory testing, testers do not follow any pattern and use their out of box thinking and diverse ideas to see how the application performs.

Following this process covers even the smallest part of the application and helps in finding more issues/bugs than in the normal test case testing process.

Exploratory testing is usually performed in cases when:

• There is a experienced tester in the testing team who can use their testing experience to apply all the best possible scenarios.
• All critical paths have been covered and major test cases are prepared as per the requirement specifications that have been executed.
• There is a critical application and no possible cases can be missed in any case.
• New tester has entered the team, exploring the application will help them understand better as well as they will follow their own mind while executing any scenario rather than following the path as mentioned in the requirement document.

9. For Any Web Application, What Are The Possible Login Features That Should Be Tested?

Listed below are the possible scenarios that can be performed to fully test the login feature of any application:

• Check the input fields i.e. Username and password with both valid and invalid values.
• Try entering valid email id with an incorrect password and also enter an invalid email and valid password. Check for the proper error message displayed.
• Enter valid credentials and get logged in to the application. Close and reopen the browser to check if still logged in.
• Enter the application after logging in and then again navigate back to the login page to check whether the user is asked again to login or not.
• Sign in from one browser and open the application from another browser to verify whether you are logged into another browser also or not.
• Change password after logging into the application and then try to login with that old password.
• There are few other possible scenarios as well which can be tested.

10. Explain Accessibility Testing And Its Importance In The Present Scenario?

Accessibility testing is a form of usability testing what testing is performed to ensure that the application can be easily handled by people with disabilities like hearing, colour blindness, low visibility etc. In today’s scenario, the web has acquired the major place in our life in the form of e-commerce sites, e-learning, e-payments, etc.

Thus in order to grow better in life, everyone should be able to be a part of technology especially people with some disabilities.

Enlisted below are few types of software which helps and assist people with disabilities to use technology:

• Speech recognition software
• Screen reader software
• Screen magnification software
• Special keyboard

11. What Is Adhoc Testing?

Adhoc testing, usually known as random testing is a form of testing which does not follow any test case or requirement of the application. Adhoc testing is basically an unplanned activity where any part of the application is randomly checked to find defects.

In such cases, the defects encountered are very difficult to reproduce as no planned test cases are followed. Adhoc testing is usually performed when there is a limited time to perform elaborative testing.

12. What Is Equivalence Partitioning?

Equivalence partitioning also known as equivalence class partitioning is a form of black box testing where input data is being divided into data classes. This process is done in order to reduce the number of test cases, but still covering the maximum requirement.

Equivalence partitioning technique is applied where input data values can be divided into ranges. The range of the input values is defined in such a way that only one condition from each range partition is to be tested assuming that all the other conditions of the same partition will behave the same for the software.

For Example
: To identify the rate of interest as per the balance in the account, we can identify the range of balance amount in the account that earn a different rate of interest.

13. Explain Boundary Value Analysis?

Boundary value analysis method checks the boundary values of Equivalence class partitions. Boundary value analysis is basically a testing technique which identifies the errors at the boundaries rather than within the range values.

For Example:
 An input field can allow a minimum of 8 characters and maximum 12 characters then 8-12 is considered as the valid range and 13 are considered as the invalid range. Accordingly, the test cases are written for valid partition value, exact boundary value, and invalid partition value.

14. When Do We Perform Smoke Testing?

Smoke testing is performed on the application after receiving the build. Tester usually tests for the critical path and not the functionality in deep to make sure, whether the build is to be accepted for further testing or to be rejected in case of broken application.

A smoke checklist usually contains the critical path of the application without which an application is blocked.

15. What Do You Understand By Sanity Testing?

Sanity testing is performed after receiving the build to check the new functionality/defects to be fixed. In this form of testing the goal is to check the functionality roughly as expected and determine whether the bug is fixed and also the effect of the fixed bug on the application under test.

There is no point in accepting the build by the tester and wasting time if Sanity testing fails.

16. What Do You Understand By Requirement Traceability Matrix?

Requirement Traceability matrix (RTM) is a tool to keep a track of requirement coverage over the process of testing.

In RTM, all requirements are categorized as their development in course of sprint and their respective ids (new feature implementation/ enhancement/ previous issues, etc) are maintained for keeping a track that everything mentioned in the requirement document has been implemented before the release of the product.

RTM is created as soon as the requirement document is received and is maintained till the release of the product.

17. What Are The Factors To Be Considered In Risk-based Testing?

By Risk-based testing of a project, it is not just to deliver a project risk-free but the main aim of risk-based testing is to achieve the project outcome by carrying out best practices of risk management.

The major factors to be considered in Risk-based testing are as follows:

• To identify when and how to implement risk-based testing on an appropriate application.
• To identify the measures that act well in finding as well as handling risk in critical areas of the application.
• To achieve the project outcome that balances risk with the quality and feature of the application.

18. Explain User Acceptance Testing?

User acceptance testing is usually performed after the product is thoroughly tested. In this form of testing, software users or say, client, itself use the application to make sure if everything is working as per the requirement and perfectly in the real world scenario.

UAT is also known as End-user testing.

1. List Out The Methods Used For Well Test Analysis?

Various methods for well test analysis are:

• Pressure drawdown tests
• Pressure build up tests
• Type curve analysis
• Pulse tests and Interference
• Drill stem and wireline formation
• Gas well tests

2. Mention What Is The Main Advantage Of Using The Pressure Drawdown Tests?

The draw down test will help you to estimate the reservoir volume.

3. Explain What Is Well Logging?

A well log is used for graphical representation of any drilling condition or subsurface features that come across while drilling, which is used for the evaluation of the well.

4. Mention What Are The Different Types Of Well Logging?

• Resistivity logs
• Spontaneous potential logs
• Gamma ray logs
• Gamma ray absorption logs
• Neutron logs
• Sonic porosity logs

5. Explain What Is Pseudo Pressure?

Pseudo pressure is a mathematical pressure function which accounts for the variable compressibility and viscosity of gas with respect to pressure.

6. Explain The Term “bull Heading”?

“Bull heading” is a process, where gas is forced back into a formation by pumping into the annulus from the surface.

7. Which Mineral Is Frequently Used To Increase The Weight Or Density Of Drilling Mud?

Barium Sulfate or BaSO4 mineral is frequently used to increase the density of drilling mud.

8. What Is The Importance Of Drilling Muds?

The drilling muds are used for:

• Lubrication purpose and for cooling of the drill bit and pipe
• It removes the cuttings that come from the bottom of the oil well
• Prevent blowouts by acting as a sealant

9. What Is The Drill-stem Testing?

Lowering a device into the drill hole to measure the pressures, it will reveal whether reservoir rock has been reached.

10. Explain What Is Hydraulic Fracturing?

Hydraulic fracturing is a technique in which tons of gallons of water, chemicals and sand at high pressure is pumped down across the drilled well. This pressurized mixture makes rock layer to crack and make small space or fissure, through which natural gas emits out.

11. What Is Proppant And What Is The Use Of It?

A proppant is a solid material, which is treated with sand or ceramic materials. It is used to keep the induced hydraulic fracture open.

12. Explain What Is Perforation In Oil Well Drilling?

A perforation is a hole made in the casing or liner of an oil well to connect it to the reservoir.

13. Explain The Term Desander And Desilter?

Desander is a centrifugal device used for removing sand from drilling the fluid to avert the abrasion of the pumps. While Desilter is a centrifugal device used to remove the slit or very fine particles.

14. Explain What Is Dogleg?

Dogleg term is used to refer for an abrupt change in direction in the wellbore, resulting in the formation of the keyseat.

15. Explain What Is Wellbore Storage?

When the oil well is shut-in, there is continue flow of fluid into the wellbore. This flow of fluid is referred as wellbore storage.

16. Explain What Is A Blowout Preventer?

Blowout preventer is installed on the top of the well and is used to control the back pressure produced by oil during the drilling process.

17. Explain What Is Annular Blowout Preventer?

Annular blowout preventer is usually a large valve, installed above the ram preventers, it forms a protective seal in the annular space between the pipes and well bore. It seals the annulus between the Kelly, drill collar and drill pipe.

18. Explain What Is Die Insert?

Die insert is a hard steel, a serrated piece which is removable and fits into the jaws of the tongs and firmly holds the body of the drill pipe, drill collars while the tongs are making up or breaking out of the pipes.

19. What Is Kelly Bushing?

Kelly bushing is a device fitted to the rotatory table through which the Kelly passes and the mean by which the torque of the rotatory table is transmitted to the Kelly and to the drill stem.

20. Explain The Term Induction Logs?

Induction logs are used in wells that do not use water or mud, but oil-based drilling fluids or air. They are non-conductive and therefore cannot use electric logs instead they use magnetism and electricity to measure resistivity.

21. Explain How Spontaneous Logs Are Useful?

Spontaneous logs determine the permeability of the rocks in the well by denoting the electrical currents produced between the drilling fluids and formation water held in the pore spaces.

22. Explain What Is Underbalanced Drilling?

The underbalanced drilling is an alternative way of drilling oil and gas wells, where the pressure in the wellbore is kept lower than the fluid pressure. The advantage of underbalanced drilling is that it reduces formation damage in reservoirs.

23. Explain The Method Of “gas Injection Down The Drill Pipe”? What Are The Advantages Of This Technique?

In this technique air or nitrogen is injected to the drilling fluid that is injected directly down the drill pipe.

The advantages of this technique is:

• Improved penetration and decreased amount of gas
• Wellbore is not required to specifically designed for underbalanced drilling
• Less amount of gas required.