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Answered 2012-12-10 14:08:13

abstract class no defination used by derieved class where virtual base class is defination that can be overriden later on

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Unlike abstract class in C++, the abstract class in C# does not have any methods defined as virtual by default. The concept of virtual are not the same between C# and C++, either. Any virtual method must be defined explicitly in C#. Related to abstract methods - interestingly, an abstract class in C# does not have to have any abstract methods. However, the reverse, if a class need to have at least one abstract method, that class must be defined as abstract.

They are not comparable, but may have some relationship between them.An abstract class is a class, while a virtual function (or method) is a method. A method must exist within a class. Hence, a class has methods, and the methods may be defined as virtual functions.A virtual function must be defined in a class, but that class does not have to be an abstract class. However, the purpose of a virtual function in C# is to provide a default behavior/implementation, while allowing the derived class to override that default implementation, hence it makes no sense to define a virtual function in a sealed class (a leaf, that is, no class can extend from it, and it is not an abstract class)Example:public class Parent {public virtual string MostCommonPhrase() {return "You better listen to me...";}}public class Child : Parent {public override string MostCommonPhrase() {return "You never listen to me...";}}

If a class has one abstract method ,the class has to be an abstract class.Methods can be implemented in abstract class.Whereas a interface is like a abstract class...the only difference being that the methods are never implemented in Interface.

Any class which has one or more abstract methods is called an abstract class. But in the normal class we can't have any abstract methods. We cannot create an object for the abstract classes. When we inherit the abstract class we should implement the abstract method which we inherit.

An abstract class is any class definition that contains at least one pure-virtual function. class AbstractClass { public: virtual void DoSomething()=0; // Pure-virtual. };

A final class cannot have any subclasses. An abstract class cannot be instantiated unless it is extended by a subclass.

Any class that has one or more pure-virtual functions is an abstract class.

Abstract class is built to promote inheritance whereas a final class is built to avoid inheritanceAn Abstract class can be extended by another class whereas a final class cannot be extended

Assume a "simple" class be a class without the keyword "abstract".You cannot create an instance of an abstract class. An abstract class is intended to be inherited from (to be extended or derived from).A "simple" class is a class that an instance can be created from (via new operator)

Some difference between an interface and an abstract class are: a. All variables in an interface are public, static and final but that is not the case in abstract classes b. An abstract class can have both abstract and concrete methods but an interface cannot have concrete methods c. An abstract class can extend other classes and implement interfaces, while an interface can only extend other interfaces.

In C++, an abstract data type is a class that must be derived into a child class. It is not possible to instantiate an abstract class. Another way to define this is to say that an abstract class contains pure virtual functions or that it inherits from a class with pure virtual functions but does not provide an implementation for them.

A more prcise description of difference is as follows.... an interface is a specification of a set of methods that the implementation class must adhere to, while an abstract class is indeed an implementation class albeit a class that is not concrete, i.e., one cannot directly instantiate an abstract class.

Association class is describing the relationship between classes. An abstract class is just 1 class, provides some abstraction behaviors that may be (but do not have to) derived, overridden from.

abstract class is a class label with abstract. It is just like a common class, with the following characterics: 1. Abstract class cannot be instantiate with an instance. 2. Abstract class may have abstract methods, while the normal class cannot have abstract methods. a virtual function in C# is a way to provide a default implementation for the class hierarchy. Both abstract class and common class (not sealed) can have virtual methods/ functions. Note that an abstract method (of an abstract class) is defining the intent, no codes (no default behavior), the implementation are left for the derived classes to do so. The virtual function if defined in an abstract class must define the implementation, the minimum is to do nothing: public abstract class Vehicle { public abstract int GetNumberOfTires(); public virtual void Move() { // default is doing nothing} } public class Car : Vehicle { public override int GetNumberOfTires() { return 4; } public override void Move() { throws new OutOfFuelExpection(); } }

Abstract classes are classes that can't be instantiated directly. In other words, you are meant to create subclasses, which you instantiate.

We make a virtual function pure whenever we wish to make our class an abstract base class (an abstract data type). Unlike a virtual function, pure virtual functions must be overridden by a derived class or by one of its derivatives (the function remains pure virtual until it is overridden, at which point it becomes virtual). Derived classes that do not provide a complete implementation for all the pure virtual functions it inherits become abstract themselves. You cannot instantiate an abstract base class other than through derivation.

an abstract class is nothing but class which contains both abstract and concrete methods for abstract class we r nt create object Syntax for pure abstract class is abstract class x { public void abstract y(); public void abstract z(); public void abc() { }

In general programming terms, a concrete class is one which can be instantiated, while an abstract class can only be instantiated via a fully implemented subclass.

There is no difference with method declaration and implementation between abstract and non-abstract classes. You do the exact same thing when writing a concrete method in either an abstract or non-abstract class.

Below is the main difference between the 3 components:Concrete class - Provides implementation for all its methods & also for methods from extended abstract classes or implemented interfacesAbstract class - Does not provide implementation for one or more of its methodsInterface - Does not provide implementation for any of its methods

All the methods declared inside an Interface are abstract. Where as abstract class must have at least one abstract method and others may be concrete or abstract. In Interface we need not use the keyword abstract for the methods.

The difference are:An abstract class can have methods that actually have code inside them whereas an Interface cannot (An Interface can be thought of as a 100% pure abstract class)All variables in an Interface are public, static, final whereas that is not the case in Abstract classes

An abstract class is a class that contains at least one pure virtual function. A definition is not needed for pure virtual functions, as derived classes must override them. virtual void foo() = 0; Abstract classes cannot be instantiated. They provide a template for derived classes, and you can also point to them with pointers to utilize polymorphism. Additionally, a class derived from an abstract class must override ALL of the pure virtual functions, in order to make the class concrete. Implementing fewer than all of them will automatically make the derived class abstract, and instantiation of the derived class will not be possible.

A pure virtual function can not be instanced directly, only in a derived class. A normal virtual function has no such requirement.

An abstract class can have a combination of abstract methods and normal methods. Interfaces cannot implement any methods themselves, all have to be abstract. Other classes can extend only one class (abstract or not), but can implement as many interfaces as they want.

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