1. What
is C++?
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.
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++.
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++.
2. How do you find
out if a linked-list has an end? (i.e. the list is not a cycle)
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.
3.
What is the difference between realloc() and free()?
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.
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.
4.
Base class has some virtual method and derived class has a method with
the same name. If we initialize the base class pointer with derived object,
calling of that virtual method will result in which method being called?
a. Base method
b. Derived method
Ans. B
b. Derived method
Ans. B
5.
What is function overloading and operator overloading?
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).
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).
6.
What are the advantages of inheritance?
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.
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.
7.
What is the difference between declaration and definition?
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; }
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; }
8.
How do you write a function that can reverse a linked-list?
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;
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;
}
}
9.
What do you mean by inline function?
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.
10. Write
a program that ask for user input from 5 to 9 then calculate the average
#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;
}
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;
}
11. Write
a short code using C++ to print out all odd number from 1 to 100 using a for loop
for( unsigned int i = 1; i < = 100; i++ )
if( i & 0x00000001 )
cout << i << \",\";
for( unsigned int i = 1; i < = 100; i++ )
if( i & 0x00000001 )
cout << i << \",\";
12. What
is public, protected, private?
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.
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.
13. 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\");
}
}
OK, why does this work?
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.
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\");
}
}
OK, why does this work?
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.
14. What
is virtual constructors/destructors?
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.
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.
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.
15.
Does c++ support multilevel and multiple inheritance?
Yes.
Yes.
16.
What are the advantages of inheritance?
• 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.
• 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.
17.
What is the difference between declaration and definition?
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<<”*”;
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; }
18. What
is the difference between an array and a list?
Array is collection of homogeneous elements. List is collection of
heterogeneous elements.
For Array memory allocated is static and continuous. For List
memory allocated is dynamic and Random.
Array: User need not have to keep in track of next memory
allocation.
List: User has to keep in Track of next location where memory is
allocated.
Array uses direct access of stored members, list uses sequencial
access for members.
//With Array you have direct access to memory position 5
Object x = a[5]; // x takes directly a reference to 5th element of
array
//With the list you have to cross all previous nodes in order to
get the 5th node:
list mylist;
list::iterator it;
for( it = list.begin() ; it != list.end() ; it++ )
{
if( i==5)
{
x = *it;
break;
}
i++;
}
19. What
is a template?
Templates allow to create generic functions that admit any data
type as parameters and return value without having to overload the function
with all the possible data types. Until certain point they fulfill the
functionality of a macro. Its prototype is any of the two following ones:
template <class indetifier> function_declaration; template
<typename indetifier> function_declaration;
The only difference between both prototypes is the use of keyword
class or typename, its use is indistinct since both expressions have exactly
the same meaning and behave exactly the same way.
20. Define
a constructor - What it is and how it might be called (2 methods).
Constructor is a member function of the class, with the name of
the function being the same as the class name. It also specifies how the object
should be initialized.
Ways of calling constructor:
1) Implicitly: automatically by complier when an object is
created.
2) Calling the constructors explicitly is possible, but it makes
the code unverifiable.
class Point2D{
int x; int y;
public Point2D() : x(0) , y(0) {} //default (no argument)
constructor
};
main(){
Point2D MyPoint; // Implicit Constructor call. In order to
allocate memory on stack, the default constructor is implicitly called.
Point2D * pPoint = new Point2D(); // Explicit Constructor call. In
order to allocate memory on HEAP we call the default constructor.
You have two pairs: new() and delete() and another pair : alloc()
and free().
21. Explain differences between eg. new() and malloc()
1.) “new and delete” are preprocessors while “malloc() and free()”
are functions. [we dont use brackets will calling new or delete].
2.) no need of allocate the memory while using “new” but in
“malloc()” we have to use “sizeof()”.
3.) “new” will initlize the new memory to 0 but “malloc()” gives
random value in the new alloted memory location [better to use calloc()]
new() allocates continous space for the object instace malloc()
allocates distributed space.
new() is castless, meaning that allocates memory for this specific
type,
malloc(), calloc() allocate space for void * that is cated to the
specific class type pointer.
22. What is the difference between class and structure?
Structure: Initially (in C) a structure was used to bundle different type of data types together to perform a particular functionality. But C++ extended the structure to contain functions also. The major difference is that all declarations inside a structure are by default public.
Structure: Initially (in C) a structure was used to bundle different type of data types together to perform a particular functionality. But C++ extended the structure to contain functions also. The major difference is that all declarations inside a structure are by default public.
Class: Class is a successor of Structure. By default all the
members inside the class are private.
23. What is RTTI?
Runtime type identification (RTTI) lets you find the dynamic type
of an object when you have only a pointer or a reference to the base type. RTTI
is the official way in standard C++ to discover the type of an object and to
convert the type of a pointer or reference (that is, dynamic typing).
24.What is encapsulation?
Packaging an object’s variables within its methods is called
encapsulation.
25.Explain term “Polymorphism” and give an example using eg. SHAPE
object: If I have a base class SHAPE, how would I define DRAW methods for two
objects CIRCLE and SQUARE
“Polymorphism”: A phenomenon which enables an object to react
differently to the same function call. in C++ it is attained by using a keyword
virtual
Example
public class SHAPE
{
public virtual void SHAPE::DRAW()=0;
}
Note here the function DRAW() is pure virtual which means the sub
classes must implement the DRAW() method and SHAPE cannot be instatiated
public class CIRCLE::public SHAPE
{
public void CIRCLE::DRAW()
{
// TODO drawing circle
}
}
public class SQUARE::public SHAPE
{
public void SQUARE::DRAW()
{
// TODO drawing square
}
}
now from the user class the calls would be like globally
SHAPE *newShape;
When user action is to draw
public void MENU::OnClickDrawCircle(){
newShape = new CIRCLE();
}
public void MENU::OnClickDrawCircle(){
newShape = new SQUARE();
}
the when user actually draws
public void CANVAS::OnMouseOperations(){
newShape->DRAW();
}
class SHAPE{
public virtual Draw() = 0; //abstract class with a pure virtual
method
};
class CIRCLE{
public int r;
public virtual Draw() { this->drawCircle(0,0,r); }
};
class SQURE
public int a;
public virtual Draw() { this->drawRectangular(0,0,a,a); }
};
Each object is driven down from SHAPE implementing Draw() function
in its own way.
26. What is an object?
Object is a software bundle of variables and related methods.
Objects have state and behavior.
27. How can you tell what shell you are running on UNIX system?
You can do the Echo $RANDOM. It will return a undefined variable
if you are from the C-Shell, just a return prompt if you are from the Bourne
shell, and a 5 digit random numbers if you are from the Korn shell. You could
also do a ps -l and look for the shell with the highest PID.
28. What do you mean by inheritance?
Inheritance is the process of creating new classes, called derived
classes, from existing classes or base classes. The derived class inherits all
the capabilities of the base class, but can add embellishments and refinements
of its own.
29.Describe PRIVATE, PROTECTED and PUBLIC – the differences and
give examples.
class Point2D{
int x; int y;
public int color;
protected bool pinned;
public Point2D() : x(0) , y(0) {} //default (no argument)
constructor
};
Point2D MyPoint;
You cannot directly access private data members when they are
declared (implicitly) private:
MyPoint.x = 5; // Compiler will issue a compile ERROR
//Nor yoy can see them:
int x_dim = MyPoint.x; // Compiler will issue a compile ERROR
On the other hand, you can assign and read the public data
members:
MyPoint.color = 255; // no problem
int col = MyPoint.color; // no problem
With protected data members you can read them but not write them:
MyPoint.pinned = true; // Compiler will issue a compile ERROR
bool isPinned = MyPoint.pinned; // no problem
30. What is namespace?
Namespaces allow us to group a set of global classes, objects
and/or functions under a name. To say it somehow, they serve to split the
global scope in sub-scopes known as namespaces.
The form to use namespaces is:
namespace identifier { namespace-body }
Where identifier is any valid identifier and namespace-body is the
set of classes, objects and functions that are included within the namespace.
For example:
namespace general { int a, b; } In this case, a and b are normal
variables integrated within the general namespace. In order to access to these
variables from outside the namespace we have to use the scope operator ::. For
example, to access the previous variables we would have to put:
general::a general::b
The functionality of namespaces is specially useful in case that
there is a possibility that a global object or function can have the same name
than another one, causing a redefinition error.
31. What is a COPY CONSTRUCTOR and when is it called?
A copy constructor is a method that accepts an object of the same
class and copies it’s data members to the object on the left part of
assignment:
class Point2D{
int x; int y;
public int color;
protected bool pinned;
public Point2D() : x(0) , y(0) {} //default (no argument)
constructor
public Point2D( const Point2D & ) ;
};
Point2D::Point2D( const Point2D & p )
{
this->x = p.x;
this->y = p.y;
this->color = p.color;
this->pinned = p.pinned;
}
main(){
Point2D MyPoint;
MyPoint.color = 345;
Point2D AnotherPoint = Point2D( MyPoint ); // now AnotherPoint has
color = 345
32. What is Boyce Codd Normal form?
A relation schema R is in BCNF with respect to a set F of functional
dependencies if for all functional dependencies in F+ of the form a-> ,
where a and b is a subset of R, at least one of the following holds:
* a- > b is a trivial functional dependency (b is a subset of
a)
* a is a superkey for schema R
33. What is virtual class and friend class?
Friend classes are used when two or more classes are designed to
work together and need access to each other's implementation in ways that the
rest of the world shouldn't be allowed to have. In other words, they help keep
private things private. For instance, it may be desirable for class
DatabaseCursor to have more privilege to the internals of class Database than
main() has.
34. What is the word you will use when defining a function in base
class to allow this function to be a polimorphic function?
virtual
35. What do you mean by binding of data and functions?
Encapsulation.
36. What are 2 ways of exporting a function from a DLL?
1. Taking a reference to the function from the DLL instance.
2. Using the DLL ’s Type Library
37. What is the difference between an object and a class?
Classes and objects are separate but related concepts. Every
object belongs to a class and every class contains one or more related objects.
- A Class is static. All of the attributes of a class are fixed
before, during, and after the execution of a program. The attributes of a class
don't change.
- The class to which an object belongs is also (usually) static.
If a particular object belongs to a certain class at the time that it is created
then it almost certainly will still belong to that class right up until the
time that it is destroyed.
- An Object on the other hand has a limited lifespan. Objects are
created and eventually destroyed. Also during that lifetime, the attributes of
the object may undergo significant change.
38. What is a class?
Class is a user-defined data type in C++. It can be created to
solve a particular kind of problem. After creation the user need not know the
specifics of the working of a class.
39. What is friend function?
As the name suggests, the function acts as a friend to a class. As
a friend of a class, it can access its private and protected members. A friend
function is not a member of the class. But it must be listed in the class
definition.
40. Which recursive sorting technique always makes recursive calls
to sort subarrays that are about half size of the original array?
Mergesort always makes recursive calls to sort subarrays that are
about half size of the original array, resulting in O(n log n) time.
41. What is abstraction?
Abstraction is of the process of hiding unwanted details from the
user.
42. What are virtual functions?
A virtual function allows derived classes to replace the
implementation provided by the base class. The compiler makes sure the
replacement is always called whenever the object in question is actually of the
derived class, even if the object is accessed by a base pointer rather than a
derived pointer. This allows algorithms in the base class to be replaced in the
derived class, even if users don't know about the derived class.
43.What is the difference between an external iterator and an
internal iterator? Describe an advantage of an external iterator.
An internal iterator is implemented with member functions of the
class that has items to step through. .An external iterator is implemented as a
separate class that can be "attach" to the object that has items to
step through. .An external iterator has the advantage that many difference
iterators can be active simultaneously on the same object.
44. What is a scope resolution operator?
A scope resolution operator (::), can be used to define the member
functions of a class outside the class.
45. What do you mean by pure virtual functions?
A pure virtual member function is a member function that the base
class forces derived classes to provide. Normally these member functions have
no implementation. Pure virtual functions are equated to zero.
class Shape { public: virtual void draw() = 0; };
46. What is polymorphism? Explain with an example?
"Poly" means "many" and "morph"
means "form". Polymorphism is the ability of an object (or reference)
to assume (be replaced by) or become many different forms of object.
Example: function overloading, function overriding, virtual functions.
Another example can be a plus ‘+’ sign, used for adding two integers or for
using it to concatenate two strings.
47.What’s the output of the following program? Why?
#include <stdio.h>
main()
{
typedef union
{
int a;
char b[10];
float c;
}
Union;
Union x,y = {100};
x.a = 50;
strcpy(x.b,\"hello\");
x.c = 21.50;
printf(\"Union x : %d %s %f \n\",x.a,x.b,x.c );
printf(\"Union y :%d %s%f \n\",y.a,y.b,y.c);
}
Given inputs X, Y, Z and operations | and & (meaning bitwise
OR and AND, respectively)
What is output equal to in
output = (X & Y) | (X & Z) | (Y & Z)
48. Why arrays are usually processed with for loop?
The real power of arrays comes from their facility of using an
index variable to traverse the array, accessing each element with the same
expression a[i]. All the is needed to make this work is a iterated statement in
which the variable i serves as a counter, incrementing from 0 to a.length -1.
That is exactly what a loop does.
49. What is an HTML tag?
An HTML tag is a syntactical construct in the HTML language that
abbreviates specific instructions to be executed when the HTML script is loaded
into a Web browser. It is like a method in Java, a function in C++, a procedure
in Pascal, or a subroutine in FORTRAN.
50.Explain which of the following declarations will compile and
what will be constant - a pointer or the value pointed at: * const char *
* char const *
* char * const
51. What problems might the following macro bring to the
application?
#define sq(x) x*x
52. Anything wrong with this code?
T *p = new T[10];
delete p;
Everything is correct, Only the first element of the array will be
deleted”, The entire array will be deleted, but only the first element
destructor will be called.
53. Anything wrong with this code?
T *p = 0;
delete p;
Yes, the program will crash in an attempt to delete a null
pointer.
54. How do you decide which integer type to use?
It depends on our requirement. When we are required an integer to
be stored in 1 byte (means less than or equal to 255) we use short int, for 2
bytes we use int, for 8 bytes we use long int.
A char is for 1-byte integers, a short is for 2-byte integers, an
int is generally a 2-byte or 4-byte integer (though not necessarily), a long is
a 4-byte integer, and a long long is a 8-byte integer.
55. What does extern mean in a function declaration?
Using extern in a function declaration we can make a function such
that it can used outside the file in which it is defined.
An extern variable, function definition, or declaration also makes
the described variable or function usable by the succeeding part of the current
source file. This declaration does not replace the definition. The declaration
is used to describe the variable that is externally defined.
If a declaration for an identifier already exists at file scope,
any extern declaration of the same identifier found within a block refers to
that same object. If no other declaration for the identifier exists at file
scope, the identifier has external linkage.
56. What can I safely assume about the initial values of variables
which are not explicitly initialized?
It depends on complier which may assign any garbage value to a
variable if it is not initialized.
57. What is the difference between char a[] = “string”; and char
*p = “string”;?
In the first case 6 bytes are allocated to the variable a which is
fixed, where as in the second case if *p is assigned to some other value the
allocate memory can change.
58. What’s the auto keyword good for?
Not much. It declares an object with automatic storage duration.
Which means the object will be destroyed at the end of the objects scope. All
variables in functions that are not declared as static and not dynamically
allocated have automatic storage duration by default.
For example
int main()
{
int a; //this is the same as writing “auto int a;”
}
Local variables occur within a scope; they are “local” to a
function. They are often called automatic variables because they automatically
come into being when the scope is entered and automatically go away when the
scope closes. The keyword auto makes this explicit, but local variables default
to auto auto auto auto so it is never necessary to declare something as an auto
auto auto auto.
59. What is the difference between char a[] = “string”; and char
*p = “string”; ?
a[] = “string”;
char *p = “string”;
The difference is this:
p is pointing to a constant string, you can never safely say
p[3]=’x';
however you can always say a[3]=’x';
char a[]=”string”; - character array initialization.
char *p=”string” ; - non-const pointer to a const-string.( this is
permitted only in the case of char pointer in C++ to preserve backward
compatibility with C.)
60. How do I declare an array of N pointers to functions returning
pointers to functions returning pointers to characters?
If you want the code to be even slightly readable, you will use
typedefs.
typedef char* (*functiontype_one)(void);
typedef functiontype_one (*functiontype_two)(void);
functiontype_two myarray[N]; //assuming N is a const integral
61. What does extern mean in a function declaration?
It tells the compiler that a variable or a function exists, even
if the compiler hasn’t yet seen it in the file currently being compiled. This
variable or function may be defined in another file or further down in the
current file.
62. How do I initialize a pointer to a function?
This is the way to initialize a pointer to a function
void fun(int a)
{
}
void main()
{
void (*fp)(int);
fp=fun;
fp(1);
}
63. How do you link a C++ program to C functions?
By using the extern "C" linkage specification around the
C function declarations.
64. Explain the scope resolution operator.
It permits a program to reference an identifier in the global
scope that has been hidden by another identifier with the same name in the
local scope.
65. What are the differences between a C++ struct and C++ class?
The default member and base-class access specifier are different.
66. How many ways are there to initialize an int with a constant?
Two. There are two formats for initializers in C++ as shown in the
example that follows. The first format uses the traditional C notation. The
second format uses constructor notation.
int foo = 123;
int bar (123);
67. How does throwing and catching exceptions differ from using
setjmp and longjmp?
The throw operation calls the destructors for automatic objects
instantiated since entry to the try block.
68. What is a default constructor?
Default constructor WITH arguments class B { public: B (int m = 0)
: n (m) {} int n; }; int main(int argc, char *argv[]) { B b; return 0; }
69. What is a conversion constructor?
A constructor that accepts one argument of a different type.
70. What is the difference between a copy constructor and an
overloaded assignment operator?
A copy constructor constructs a new object by using the content of
the argument object. An overloaded assignment operator assigns the contents of
an existing object to another existing object of the same class.
71. When should you use multiple inheritance?
There are three acceptable answers: "Never," "Rarely,"
and "When the problem domain cannot be accurately modeled any other
way."
72. Explain the ISA and HASA class relationships. How would you
implement each in a class design?
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.
73. When is a template a better solution than a base class?
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.
74. What is a mutable member?
One that can be modified by the class even when the object of the
class or the member function doing the modification is const.
75. What is an explicit constructor?
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.
76. What is the Standard Template Library (STL)?
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.
77. Describe run-time type identification.
The ability to determine at run time the type of an object by
using the typeid operator or the dynamic cast operator.
78. What problem does the namespace feature solve?
Multiple providers of libraries might use common global
identifiers causing a name collision when an application tries to link with two
or more such libraries. The namespace feature surrounds a library’s external
declarations with a unique namespace that eliminates the potential for those
collisions.
This solution assumes that two library vendors don’t use the same
namespace identifier, of course.
79. Are there any new intrinsic (built-in) data types?
Yes. The ANSI committee added the bool intrinsic type and its true
and false value keywords.
80. Will the following program execute?
void main()
{
void *vptr = (void *) malloc(sizeof(void));
vptr++;
}
It will throw an error, as arithmetic operations cannot be
performed on void pointers.
81. For the following C program
#define AREA(x)(3.14*x*x)
main()
{
float r1=6.25,r2=2.5,a;
float r1=6.25,r2=2.5,a;
a=AREA(r1);
printf("\n Area of the circle is %f", a);
a=AREA(r2);
printf("\n Area of the circle is %f", a);
}
What is the output?
Ans. Area of the circle is 122.656250
Area of the circle is 19.625000
82. void main()
{
int d=5;
printf("%f",d);
}
Ans: Undefined
83. void main()
{
int i;
for(i=1;i<4,i++)
switch(i)
case 1: printf("%d",i);break;
{
case 2:printf("%d",i);break;
case 3:printf("%d",i);break;
}
switch(i) case 4:printf("%d",i);
}
Ans: 1,2,3,4
84.void main()
{
char *s="\12345s\n";
printf("%d",sizeof(s));
}
Ans: 6
85.void main()
{
unsigned i=1; /* unsigned char k= -1 => k=255; */
signed j=-1; /* char k= -1 => k=65535 */
/* unsigned or signed int k= -1 =>k=65535 */
if(i<j)
printf("less");
else
if(i>j)
printf("greater");
else
if(i==j)
printf("equal");
}
Ans: less</j)
86. void main()
{
float j;
j=1000*1000;
printf("%f",j);
}
1. 1000000
2. Overflow
3. Error
4. None
Ans: 4
87. How do you declare an array of N pointers to functions
returning pointers to functions returning pointers to characters?
Ans: The first part of this question can be answered in at least
three ways:
1. char *(*(*a[N])())();
2. Build the declaration up incrementally, using typedefs:
typedef char *pc; /* pointer to char */
typedef pc fpc(); /* function returning pointer to char */
typedef fpc *pfpc; /* pointer to above */
typedef pfpc fpfpc(); /* function returning... */
typedef fpfpc *pfpfpc; /* pointer to... */
pfpfpc a[N]; /* array of... */
1. char *(*(*a[N])())();
2. Build the declaration up incrementally, using typedefs:
typedef char *pc; /* pointer to char */
typedef pc fpc(); /* function returning pointer to char */
typedef fpc *pfpc; /* pointer to above */
typedef pfpc fpfpc(); /* function returning... */
typedef fpfpc *pfpfpc; /* pointer to... */
pfpfpc a[N]; /* array of... */
3. Use the cdecl program, which turns English into C and vice
versa:
cdecl> declare a as array of pointer to function returning
pointer to function returning pointer to char
char *(*(*a[])())()
char *(*(*a[])())()
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