What is a dangling pointer?
A dangling pointer arises when you use the address of an object after
its lifetime is over. This may occur in situations like returning
addresses of the automatic variables from a function or using the
address of the memory block after it is freed. The following
code snippet shows this:
class Sample
{
public:
int *ptr;
Sample(int i)
{
ptr = new int(i);
}
~Sample()
{
delete ptr;
}
void PrintVal()
{
cout << "The value is " << *ptr; } }; void SomeFunc(Sample x) { cout << "Say i am in someFunc " << endl; } int main() { Sample s1 = 10; SomeFunc(s1); s1.PrintVal(); }In the above example when PrintVal() function is called it is called by the pointer that has been freed by the destructor in SomeFunc. How many ways can an argument be passed to a subroutine?
An argument can be passed in two ways. They are Pass by Value and Passing by Reference.
Passing by value: This method copies the value of an argument into the formal parameter of the subroutine.
Passing by reference: In this method, a reference to an argument (not the value of the argument) is passed to the parameter.
What is the difference between procedural and object-oriented programs?
1. In procedural program, programming logic follows certain procedures and the instructions are executed one after another. In OOP program, unit of program is object, which is nothing but combination of data and code.
2. In procedural program, data is exposed to the whole program whereas in OOPs program, it is accessible with in the object and which in turn assures the security of the code.
What are the advantages of OOPL?
Object oriented programming languages directly represent the real life objects. The features of OOPL as inheritance, polymorphism, encapsulation makes it powerful.
Can a method be overloaded based on different return type but same argument type ?
No, because the methods can be called without using their return type in which case there is ambiguity for the compiler.
What is Downcasting ?
Downcasting is the casting from a general to a more specific type, i.e. casting down the hierarchy.
What is meant by ?method-wars??
Before 1994 there were different methodologies like Rumbaugh, Booch, Jacobson, Meyer etc who followed their own notations to model the systems. The developers were in a dilemma to choose the method which best accomplishes their needs. This particular span was called as ?method-wars?
Differentiate Aggregation and containment?
Aggregation is the relationship between the whole and a part. We can add/subtract some properties in the part (slave) side. It won?t affect the whole part.
Best example is Car, which contains the wheels and some extra parts. Even though the parts are not there we can call it as car.
But, in the case of containment the whole part is affected when the part within that got affected. The human body is an apt example for this relationship. When the whole body dies the parts (heart etc) are died.
Differentiate persistent & non-persistent objects?
Persistent refers to an object?s ability to transcend time or space. A persistent object stores/saves its state in a permanent storage system with out losing the information represented by the object.
A non-persistent object is said to be transient or ephemeral. By default objects are considered as non-persistent.
List out some of the object-oriented methodologies.
Object Oriented Development (OOD) (Booch 1991,1994).
Object Oriented Analysis and Design (OOA/D) (Coad and Yourdon 1991).
Object Modeling Techniques (OMT) (Rumbaugh 1991).
Object Oriented Software Engineering (Objectory) (Jacobson 1992).
Object Oriented Analysis (OOA) (Shlaer and Mellor 1992).
The Fusion Method (Coleman 1991).
When does a name clash occur?
A name clash occurs when a name is defined in more than one place. For example., two different class libraries could give two different classes the same name. If you try to use many class libraries at the same time, there is a fair chance that you will be unable to compile or link the program because of name clashes.
Does a class inherit the constructors of its superclass?
A class does not inherit constructors from any of its super classes.
If a class is declared without any access modifiers, where may the class be accessed?
A class that is declared without any access modifiers is said to have package access. This means that the class can only be accessed by other classes and interfaces that are defined within the same package.
)
What is the difference between shadow and override?
Overriding is used to redefines only the methods, but shadowing redefines the entire element.
What is multithreading?
Multithreading is the mechanism in which more than one thread run independent of each other within the process.
What are inner class and anonymous class?
Inner class : classes defined in other classes, including those defined in methods are called inner classes. An inner class can have any accessibility including private. Anonymous class : Anonymous class is a class defined inside a method without a name and is instantiated and declared in the same place and cannot have explicit constructors.
What is the difference between superclass and subclass?
A super class is a class that is inherited whereas sub class is a class that does the inheriting.
What is difference between overloading and overriding?
a) In overloading, there is a relationship between methods available in the same class whereas in overriding, there is relationship between a superclass method and subclass method.
b) Overloading does not block inheritance from the superclass whereas overriding blocks inheritance from the superclass.
c) In overloading, separate methods share the same name whereas in overriding, subclass method replaces the superclass.
d) Overloading must have different method signatures whereas overriding must have same signature
A dangling pointer arises when you use the address of an object after
its lifetime is over. This may occur in situations like returning
addresses of the automatic variables from a function or using the
address of the memory block after it is freed. The following
code snippet shows this:
class Sample
{
public:
int *ptr;
Sample(int i)
{
ptr = new int(i);
}
~Sample()
{
delete ptr;
}
void PrintVal()
{
cout << "The value is " << *ptr; } }; void SomeFunc(Sample x) { cout << "Say i am in someFunc " << endl; } int main() { Sample s1 = 10; SomeFunc(s1); s1.PrintVal(); }In the above example when PrintVal() function is called it is called by the pointer that has been freed by the destructor in SomeFunc. How many ways can an argument be passed to a subroutine?
An argument can be passed in two ways. They are Pass by Value and Passing by Reference.
Passing by value: This method copies the value of an argument into the formal parameter of the subroutine.
Passing by reference: In this method, a reference to an argument (not the value of the argument) is passed to the parameter.
What is the difference between procedural and object-oriented programs?
1. In procedural program, programming logic follows certain procedures and the instructions are executed one after another. In OOP program, unit of program is object, which is nothing but combination of data and code.
2. In procedural program, data is exposed to the whole program whereas in OOPs program, it is accessible with in the object and which in turn assures the security of the code.
What are the advantages of OOPL?
Object oriented programming languages directly represent the real life objects. The features of OOPL as inheritance, polymorphism, encapsulation makes it powerful.
Can a method be overloaded based on different return type but same argument type ?
No, because the methods can be called without using their return type in which case there is ambiguity for the compiler.
What is Downcasting ?
Downcasting is the casting from a general to a more specific type, i.e. casting down the hierarchy.
What is meant by ?method-wars??
Before 1994 there were different methodologies like Rumbaugh, Booch, Jacobson, Meyer etc who followed their own notations to model the systems. The developers were in a dilemma to choose the method which best accomplishes their needs. This particular span was called as ?method-wars?
Differentiate Aggregation and containment?
Aggregation is the relationship between the whole and a part. We can add/subtract some properties in the part (slave) side. It won?t affect the whole part.
Best example is Car, which contains the wheels and some extra parts. Even though the parts are not there we can call it as car.
But, in the case of containment the whole part is affected when the part within that got affected. The human body is an apt example for this relationship. When the whole body dies the parts (heart etc) are died.
Differentiate persistent & non-persistent objects?
Persistent refers to an object?s ability to transcend time or space. A persistent object stores/saves its state in a permanent storage system with out losing the information represented by the object.
A non-persistent object is said to be transient or ephemeral. By default objects are considered as non-persistent.
List out some of the object-oriented methodologies.
Object Oriented Development (OOD) (Booch 1991,1994).
Object Oriented Analysis and Design (OOA/D) (Coad and Yourdon 1991).
Object Modeling Techniques (OMT) (Rumbaugh 1991).
Object Oriented Software Engineering (Objectory) (Jacobson 1992).
Object Oriented Analysis (OOA) (Shlaer and Mellor 1992).
The Fusion Method (Coleman 1991).
When does a name clash occur?
A name clash occurs when a name is defined in more than one place. For example., two different class libraries could give two different classes the same name. If you try to use many class libraries at the same time, there is a fair chance that you will be unable to compile or link the program because of name clashes.
Does a class inherit the constructors of its superclass?
A class does not inherit constructors from any of its super classes.
If a class is declared without any access modifiers, where may the class be accessed?
A class that is declared without any access modifiers is said to have package access. This means that the class can only be accessed by other classes and interfaces that are defined within the same package.
)
What is the difference between shadow and override?
Overriding is used to redefines only the methods, but shadowing redefines the entire element.
What is multithreading?
Multithreading is the mechanism in which more than one thread run independent of each other within the process.
What are inner class and anonymous class?
Inner class : classes defined in other classes, including those defined in methods are called inner classes. An inner class can have any accessibility including private. Anonymous class : Anonymous class is a class defined inside a method without a name and is instantiated and declared in the same place and cannot have explicit constructors.
What is the difference between superclass and subclass?
A super class is a class that is inherited whereas sub class is a class that does the inheriting.
What is difference between overloading and overriding?
a) In overloading, there is a relationship between methods available in the same class whereas in overriding, there is relationship between a superclass method and subclass method.
b) Overloading does not block inheritance from the superclass whereas overriding blocks inheritance from the superclass.
c) In overloading, separate methods share the same name whereas in overriding, subclass method replaces the superclass.
d) Overloading must have different method signatures whereas overriding must have same signature
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