C, C++ Interview Questions Part - 1

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C, C++ Interview Questions
Part - 1

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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.
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++.

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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.

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4. 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).

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5. 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; }
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.

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7. Define Storage Classes and explain application domain?
Register: tell to the compiler for use a CPU register for fast aceess for that
variable.
Auto: It's a variable created and initialized when it is defined. It is not visible
outside of the block.
Static: defined inside of the function retain its value between calls. Always is
initialized with 0. Defined as global in a file is visible on for the functions from that
file.
Extern : The definition of the variable is in another file.
8. Define a "dangling" pointer?
Dangling pointer is obtained by using the address of an object which was freed.
9. Any difference between "const int*ptr" and int *const ptr" ?
Yes, it's a major difference. First define a constant data and second define a
constant pointer.

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10. Define the Storage Qualifiers?
const - define a variable that can not change its value along the program
execution.
volatile - define a variable that can be changed indirectly. An example can
be a counter register that is updated by hardware.
mutuable - a member of a structure or object can be changed even if the
structure, for example is declared const:
Ex: struct complex {mutuable int x; int y;};
const complex Mycomplex = {1, 2};
Mycomplex.x = 3; /* correct */
11. Does c++ support multilevel and multiple inheritance?
Yes.

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12. 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.
13. Define a constructor - What it is and how it might be called.
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.

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14. 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.
15. 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). The need came
from practical experience with C++. RTTI replaces many Interview Questions
- Homegrown versions with a solid, consistent approach.

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16. 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.
17. 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.
18. 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

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19. 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.

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20. What do you mean by binding of data and functions?
Encapsulation.
21. 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.
22. 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.

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23. 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.
24. 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.
25.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.

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