Set - 1

Question 1 :

What is C++?

Answer :

Released in 1985, C++ is an object-oriented programming language created by Bjarne Stroustrup. C++ maintains almost all aspects of the C language, while simplifying memory management and adding several features - including a new datatype known as a class (you will learn more about these later) - to allow object-oriented programming. C++ maintains the features of C which allowed for low-level memory access but also gives the programmer new tools to simplify memory management. 

C++ used for:

C++ is a powerful general-purpose programming language. It can be used to create small programs or large applications. It can be used to make CGI scripts or console-only DOS programs. C++ allows you to create programs to do almost anything you need to do. The creator of C++, Bjarne Stroustrup, has put together a partial list of applications written in C++.


Question 2 :

How do you find out if a linked-list has an end? (i.e. the list is not a cycle)

Answer :

You can find out by using 2 pointers. One of them goes 2 nodes each time. The second one goes at 1 nodes each time. If there is a cycle, the one that goes 2 nodes each time will eventually meet the one that goes slower. If that is the case, then you will know the linked-list is a cycle.


Question 3 :

What is the difference between realloc() and free()?

Answer :

The free subroutine frees a block of memory previously allocated by the malloc subroutine. Undefined results occur if the Pointer parameter is not a valid pointer. If the Pointer parameter is a null value, no action will occur. The realloc subroutine changes the size of the block of memory pointed to by the Pointer parameter to the number of bytes specified by the Size parameter and returns a new pointer to the block. The pointer specified by the Pointer parameter must have been created with the malloc, calloc, or realloc subroutines and not been deallocated with the free or realloc subroutines. Undefined results occur if the Pointer parameter is not a valid pointer.


Question 4 :

What is function overloading and operator overloading?

Answer :

Function overloading: C++ enables several functions of the same name to be defined, as long as these functions have different sets of parameters (at least as far as their types are concerned). This capability is called function overloading. When an overloaded function is called, the C++ compiler selects the proper function by examining the number, types and order of the arguments in the call. Function overloading is commonly used to create several functions of the same name that perform similar tasks but on different data types. 
Operator overloading allows existing C++ operators to be redefined so that they work on objects of user-defined classes. Overloaded operators are syntactic sugar for equivalent function calls. They form a pleasant facade that doesn't add anything fundamental to the language (but they can improve understandability and reduce maintenance costs).


Question 5 :

What is the difference between declaration and definition? 

Answer :

The declaration tells the compiler that at some later point we plan to present the definition of this declaration.
E.g.: 

void stars () //function declaration

The definition contains the actual implementation.
E.g.: 

void stars () // declarator
{
	for(int j=10; j > =0; j--) //function body
		cout << *;
		cout << endl; 
}

 


Question 6 :

What are the advantages of inheritance?

Answer :

It permits code reusability. Reusability saves time in program development. It encourages the reuse of proven and debugged high-quality software, thus reducing problem after a system becomes functional.


Question 7 :

What do you mean by inline function?

Answer :

The idea behind inline functions is to insert the code of a called function at the point where the function is called. If done carefully, this can improve the application's performance in exchange for increased compile time and possibly (but not always) an increase in the size of the generated binary executables.


Question 8 :

How do you write a function that can reverse a linked-list?

Answer :

void reverselist(void)
{
	if(head==0)
		return;
	if(head->next==0)
		return;
	if(head->next==tail){
		head->next = 0;
		tail->next = head;
	}
	else{
		node* pre = head;
		node* cur = head->next;
		node* curnext = cur->next;
		head->next = 0;
		cur-> next = head;

		for(; curnext!=0; ){
			cur->next = pre;
			pre = cur;
			cur = curnext;
			curnext = curnext->next;
		}
		curnext->next = cur;
	}
}

 


Question 9 :

Write a program that ask for user input from 5 to 9 then calculate the average

Answer :

#include "iostream.h"
int main() {
	int MAX = 4;
	int total = 0;
	int average;
	int numb;
	for (int i=0; i<MAX; i++) {
		cout << "Please enter your input between 5 and 9: ";
		cin >> numb;
		while ( numb<5 || numb>9) {
			cout << "Invalid input, please re-enter: ";
			cin >> numb;
		}
		total = total + numb;
	}
	average = total/MAX;
	cout << "The average number is: " << average << "\n";
	return 0;
}

 


Question 10 :

Write a short code using C++ to print out all odd number from 1 to 100 using a for loop 

Answer :

for( unsigned int i = 1; i < = 100; i++ )
if( i & 0x00000001 )
cout << i << \",\";

 


Question 11 :

What is public, protected, private?

Answer :

Public, protected and private are three access specifier in C++. 
Public data members and member functions are accessible outside the class. 
Protected data members and member functions are only available to derived classes. 
Private data members and member functions can't be accessed outside the class. However there is an exception can be using friend classes.


Question 12 :

Write a function that swaps the values of two integers, using int* as the argument type?

Answer :

void swap(int* a, int*b) {
	int t;
	t = *a;
	*a = *b;
	*b = t;
}

 


Question 13 :

Tell how to check whether a linked list is circular?

Answer :

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\");
	}
}

 


Question 14 :

OK, why does this work?

Answer :

If a list is circular, at some point pointer2 will wrap around and be either at the item just before pointer1, or the item before that. Either way, it's either 1 or 2 jumps until they meet.


Question 15 :

What is virtual constructors/destructors?

Answer :

Answer1
Virtual destructors:
If an object (with a non-virtual destructor) is destroyed explicitly by applying the delete operator to a base-class pointer to the object, the base-class destructor function (matching the pointer type) is called on the object.
There is a simple solution to this problem declare a virtual base-class destructor.
This makes all derived-class destructors virtual even though they don't have the same name as the base-class destructor. Now, if the object in the hierarchy is destroyed explicitly by applying the delete operator to a base-class pointer to a derived-class object, the destructor for the appropriate class is called. Virtual constructor: Constructors cannot be virtual. Declaring a constructor as a virtual function is a syntax error. 

Answer2
Virtual destructors: If an object (with a non-virtual destructor) is destroyed explicitly by applying the delete operator to a base-class pointer to the object, the base-class destructor function (matching the pointer type) is called on the object.
There is a simple solution to this problem – declare a virtual base-class destructor. This makes all derived-class destructors virtual even though they don't have the same name as the base-class destructor. Now, if the object in the hierarchy is destroyed explicitly by applying the delete operator to a base-class pointer to a derived-class object, the destructor for the appropriate class is called.


Question 16 :

Explain the ISA and HASA class relationships. How would you implement each in a class design?

Answer :

A specialized class "is" a specialization of another class and, therefore, has the ISA relationship with the other class. An Employee ISA Person. This relationship is best implemented with inheritance. Employee is derived from Person. A class may have an instance of another class. For example, an employee "has" a salary, therefore the Employee class has the HASA relationship with the Salary class. This relationship is best implemented by embedding an object of the Salary class in the Employee class.


Question 17 :

When is a template a better solution than a base class?

Answer :

When you are designing a generic class to contain or otherwise manage objects of other types, when the format and behavior of those other types are unimportant to their containment or management, and particularly when those other types are unknown (thus, the generosity) to the designer of the container or manager class.


Question 18 :

What is a mutable member?

Answer :

One that can be modified by the class even when the object of the class or the member function doing the modification is const.


Question 19 :

What is an explicit constructor? 

Answer :

A conversion constructor declared with the explicit keyword. The compiler does not use an explicit constructor to implement an implied conversion of types. It's purpose is reserved explicitly for construction.


Question 20 :

What is the Standard Template Library (STL)?

Answer :

A library of container templates approved by the ANSI committee for inclusion in the standard C++ specification. 
A programmer who then launches into a discussion of the generic programming model, iterators, allocators, algorithms, and such, has a higher than average understanding of the new technology that STL brings to C++ programming.