Infosys Interview Questions for 2015

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1. Difference between C and C++?

a) C follows the procedural programming paradigm while C++ is a multiparadigm language (procedural as well as object oriented) In case of C, importance is given to the steps or procedure of the program while C++ focuses on the data rather than the process. Also, it is easier to implement/edit the code in case of C++ for the same reason.

b) In case of C, the data is not secured while the data is secured (hidden) in C++ This difference is due to specific OOP features like Data Hiding which are not present in C.

c) C is a low­level language while C++ is a middle­level language C is regarded as a low­level language (difficult interpretation & less user friendly) while C++ has features of both low­level (concentration on what's going on in the machine hardware) & high­level languages (concentration on the program itself) & hence is regarded as a middle­level language.

d) C uses the top­down approach while C++ uses the bottom­up approach In case of C, the program is formulated step by step, each step is processed into detail while in C++, the base elements are first formulated which then are linked together to give rise to larger systems.

e) C is function­driven while C++ is object­driven Functions are the building blocks of a C program while objects are building blocks of a C++ program.

f) C++ supports function overloading while C does not Overloading means two functions having the same name in the same program. This can be done only in C++ with the help of Polymorphism (an OOP feature)

g) We can use functions inside structures in C++ but not in C. In case of C++, functions can be used 
inside a structure while structures cannot contain functions in C.

h) The NAMESPACE feature in C++ is absent in case of C C++ uses NAMESPACE which avoid name collisions. For instance, two students enrolled in the same university cannot have the same roll number while two students in different universities might have the same roll number. The universities are two different namespace & hence contain the same roll number (identifier) but the same university (one namespace) cannot have two students with the same roll number (identifier)

i) The standard input & output functions differ in the two languages C uses scanf & printf while C++ uses cin>> & cout<< as their respective input & output functions

j) C++ allows the use of reference variables while C does not Reference variables allow two variable names to point to the same memory location. We cannot use these variables in C programming.

k) C++ supports Exception Handling while C does not. C does not support it "formally" but it can always be implemented by other methods. Though you don't have the framework to throw & catch exceptions as in C++.

2. What are the 4 basics of OOP? 

Abstraction, Inheritance, Encapsulation, and Polymorphism.

3. What you mean by Object Relational DBMS?

An object-relational database (ORD), or object-relational database management system (ORDBMS), is a database management system (DBMS) similar to a relational database, but with an object-oriented database model: objects, classes and inheritance are directly supported in database schemas and in the query language. In addition, just as with proper relational systems, it supports extension of the data model with custom data-types and methods.

4. What is null pointer?

When referring to computer memory, a null pointer is a command used to direct a software program or operating system to an empty location in the computer memory. Commonly, the null pointer is used to denote the end of amemory search or processing event. In computer programming, a null pointer is a pointer that does not point to any object or function. A nil pointer is a false value. For example, 1 > 2 is a nil statement. In the programming language C, NULL is an available command that can be used, where nil is an available command used in the Pascal programming language.

5. What is database Schema?

The formal definition of database schema is a set of formulas (sentences) called integrity constraints imposed on a database.

6. What are the different levels of database schema?

Conceptual schema- a map of concepts and their relationships.
Logical schema- a map of entities and their attributes and relations
Physical schema- a particular implementation of a logical schema
Schema object- Oracle database object


7. What you mean by Object Relational DBMS?

An object­relational database (ORD), or object­relational database management system (ORDBMS), is a database management system (DBMS) similar to a relational database, but with an object­oriented database model: objects, classes and inheritance are directly supported in database schemas and in the query language. In addition, just as with proper relational systems, it supports extension of the data model with custom data­types and methods.

8. Structural difference between bitmap and b­tree index?

Btree It is made of branch nodes and leaf nodes. Branch nodes holds prefix key value along with the link to the leaf node. The leaf node in turn contains the indexed value and rowed. Bitmap It simply consists of bits for every single distinct value. It uses a string of bits to quickly locate rows in a table. Used to index low cardinality columns.

9. What is difference between foreign key and reference key ? 

Reference Key is the primary key that is referenced in the other table (linked via the other tables Foreign Key). Foreign Key is how you link the second table to the primary tables Primary Key (or Reference Key).

10. Tell how to check whether a linked list is circular.

Create two pointers, each set to the start of the list. Update each as follows: while (pointer1) { pointer1 = pointer1­>next; pointer2 = pointer2­>next; if (pointer2) pointer2=pointer2­>next; if (pointer1 == pointer2) { print ("circular\n"); } }

11. What is difference between foreign key and reference key ?

Reference Key is the primary key that is referenced in the other table (linked via the other tables Foreign Key). Foreign Key is how you link the second table to the primary tables Primary Key (or Reference Key).

12. What is WPF and WCF?

WPF/WCF application, need in .NET 3.0 Framework. This application will cover the following concepts: WCF(Windows Communication Foundation) The new service orientated attributes The use of interfaces The use of callbacksAsynchronous delegates Creating the proxy WPF( Windows Presentation Foundation ) Styles Templates Animations Databinding Multithreading a WPF application

13. Tell me about DSN?

A Data Source Name (DSN) is the logical name that is used by Open Database Connectivity (ODBC) to refer to the drive and other information that is required to access data. The name is used by Internet Information Services (IIS) for a connection to an ODBC data source, such as a Microsoft SQL Server database.

14. Tell how to check whether a linked list is circular.

Create two pointers, each set to the start of the list. Update each as follows:
while (pointer1) {
pointer1 = pointer1->next;
pointer2 = pointer2->next; if (pointer2) pointer2=pointer2->next;
if (pointer1 == pointer2) {
print (“circular\n”);
}
}
Thus, these are the most commonly asked Infosys technical interview questions.  Read these Infosys technical interview questions for better Interview process.

15. What is the difference between an EXE and a DLL? 

The term EXE is a shortened version of the word executable as it identifies the file as a program. On the other hand, DLL stands for Dynamic Link Library, which commonly contains functions and procedures that can be used by other programs.+

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