Technical Interview Questions and Answers :: Wipro
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5. Classes and Object
A virtual function, equated to zero is called a pure virtual function. It is a function declared in a base class that has no definition relative to the base class. A class containing such pure function is called an abstract class.
It objectives are
• Provide some traits to the derived classes.
• To create a base pointer required for achieving run time polymorphism.
1) Encapsulation: It is the mechanism that binds together code and data in manipulates, and keeps both safe from outside interference and misuse. In short it isolates a particular code and data from all other codes and data. A well-defined interface controls the access to that particular code and data.
2) Inheritance: It is the process by which one object acquires the properties of another object. This supports the hierarchical classification. Without the use of hierarchies, each object would need to define all its characteristics explicitly. However, by use of inheritance, an object need only define those qualities that make it unique within its class. It can inherit its general attributes from its parent. A new sub-class inherits all of the attributes of all of its ancestors.
3) Polymorphism: It is a feature that allows one interface to be used for general class of actions. The specific action is determined by the exact nature of the situation. In general polymorphism means "one interface, multiple methods"; this means that it is possible to design a generic interface to a group of related activities. This helps reduce complexity by allowing the same interface to be used to specify a general class of action. It is the compiler's job to select the specific action (that is, method) as it applies to each situation.
1. C can run most of the code of C, but C can't run C code.
2. C supports procedural programming paradigm whereas C supports both procedural and object oriented programming paradigm.
3. C is a function driven and C is an object driven language.
4. C doesn't allow function definitions within structures whereas in C function definition can be within structures.
5. C doesn't support reference variables but C does support.
1. C supports pointers, Java doesn't.
2. Multiple inheritence is supported in C but not in Java.
3. Java has built-in support for threads whereas C doesn't have built-in support for threads.
4. No destructors in Java but C has them.
5. C supports both method and operator overloading, Java only supports method overloading.
Encapsulation is binding of attributes and behaviors. Hiding the actual implementation and exposing the functionality of any object. Encapsulation is the first step towards OOPS, is the procedure of covering up of data and functions into a single unit (called class). Its main aim is to protect the data from out side world.
Yes, Consider a category table in a e-commerce web site.
Category_Id, Category_Name, Parent_Category_ID. In this table all the parent categories are also categories. When we create a self join category id will be treated as foreign key to the same table.
A FOREIGN KEY is one or more columns whose values are based on the PRIMARY or CANDITATE KEY values from the database.
The UNIQUE KEY column restricts entry of duplicate values but entry of NULL value is allowed. In case of PRIMARY KEY columns entry of duplicate as well as