Interview Questions.

Q1. How Can I Use The Paradox Engine 1.0 With C++?

Because the Paradox Engine capabilities are all compiled as C capabilities, you may need to assure that the names of the capabilities do no longer get "mangled" by using the C++ compiler. To try this you need to prototype the Engine capabilities as extern "C". In the pxengine.H header record insert the following code on the lines indicated. 

/* inserted at line # 268 */ 

#ifdef __cplusplus 

extern "C"  

#endif 

/* inserted at line # 732, just earlier than the final #endif */ 

#ifdef __cplusplus 

 #endif 

Paradox Engine version 2.Zero is "aware" of C++ and for that reason does not require any modifications to its header document.

Q2. I Was Trying To Allocate An Array Of Function Pointers Using The New Operator But I Keep Getting Declaration Syntax Errors Using The Following Syntax: New Int(*[10])(); What's Wrong?

The new operator is a unary operator and binds first to the int key-word producing the following: (new int) (*[10])(); 

You want to place parentheses around the expression to produce the expected effects: new (int (*[10]());

Q3. I Have A Class That Is Derived From Three Base Classes. Can I Insure That One Base Class Constructor Will Be Called Before All Other Constructors?

If you declare the base elegance as a digital base elegance, its constructor may be called before any non-digital base magnificence constructors. Otherwise the constructors are called in left-to-proper order on the declaration line for the magnificence.

Q4. What's The Difference Between The Keywords Struct And Class?

The contributors of a STRUCT are PUBLIC by default, whilst in CLASS, they default to PRIVATE. They are otherwise functionally equivalent.

Q5. How Can I Output Hex Values In Upper Case Using The Iostream Libraries?

You want to set the state of the circulation the usage of setf(). For instance, 

#include 

int fundamental(void) 

 

cout << hex; 

cout << "nNot higher-case : " << 255; 

cout.Setf(ios::upper-case); 

cout << "nUppercase : " << 255; 

return 0; 

Q6. Can I Statically Allocate More Than 64k Of Data In A Single Module?

Yes. Far data items are now supported: 

... 

Char far array1[60000L]; 

char far array2[60000L]; 

... 

For arrays larger than 64k use: 

char huge array3[100000L];

Q7. What Do You Mean By Binding Of Data And Functions?

Encapsulation.

Q8. Why Do I Get A "type Name Expected" Error On My Definition Of A Friend Class In My New Class?

A You need to let the compiler know that the label you use for your friend class is another class. If you do not want to define your entire class, you can simply have "class xxx", where xxx is your label.

Q9. What Does The _seg Modifier Do?

Using _seg causes a pointer to become a storage place for a segment value, rather than an offset ( or a segment/offset ). For instance, if "int _seg *x" contains the value 0x40, then when you use "*x", the value pointed to will be at segment 0x40, offset @If you add a value to the pointer, the value is multiplied by the size of the pointer type. That new value is used as an offset, and is combined with the segment value contained in the pointer. For instance, 

int _seg *x; 

int value; 

x = (int _seg *)0x40; 

value = *(x + 20); 

value is assigned the value of the integer at 0x40:0x28 

(Remember, 20 * sizeof(int) = 40 = 0x28).

Q10. What Potential Problems Can Arise From Type Casting A Base Class Pointer Into A Derived Class Pointer So That The Derived Class's Member Functions Can Be Called?

Syntactically this is allowable. There is always the possibility of a base pointer actually pointing to a base class. If this is typecast to a derived type, the method being called may not exist in the base class. Therefore, you would be grabbing the address of a function that does not exist.

Q11. 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.

Q12. 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.

Q13. What Is Abstraction?

Abstraction is of the process of hiding unwanted details from the user.

Q14. What Is Polymorphism? Explain With An Example?

"Poly" me "many" and "morph" me "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.

Q15. 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

Q16. What Is The Const Keyword Doing Here?

There is a pointer to the object for which a function is called known as the 'this' pointer. By default the type of 'this' is X *const ( a constant pointer). The const keyword changes the type to const X *const ( a constant pointer to constant data ).

Q17. If I Pass A Character To A Function Which Only Accepts An Int, What Will The Compiler Do? Will It Flag It As An Error?

No. The compiler will promote the char to an int and use the integer representation in the function instead of the character itself.

Q18. How To Write A Swap( ) Function Which Swaps The Values Of The Variables Using Bitwise Operators.?

Here is the swap( ) function.

Swap ( int *x, int *y )

*x ^= *y ;

*y ^= *x ;

*x ^= *y ;

The swap( ) function uses the bitwise XOR operator and does not require any temporary variable for swapping.

Q19. 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.

Q20. 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< function_declaration; template

function_declaration;

The most effective difference between both prototypes is using keyword class or typename, its use is

vague on the grounds that each expressions have exactly the equal that means and behave precisely the identical manner.

Q21. What Is The Difference Between An Object And A Class?

Classes and items are separate however associated principles. Every item belongs to a category and every magnificence contains one or greater associated gadgets.

A Class is static. All of the attributes of a category are constant earlier than, at some stage in, and after the execution of a application. The attributes of a class don't change.

The elegance to which an item belongs is likewise (generally) static. If a selected object belongs to a positive magnificence on the time that it is created then it almost sincerely will nonetheless belong to that class proper up till the time that it's miles destroyed.

An Object then again has a restrained lifespan. Objects are created and subsequently destroyed. Also at some stage in that lifetime, the attributes of the item might also go through big change.

Q22. What Is Virtual Class And Friend Class?

Friend instructions are used while  or more lessons are designed to paintings collectively and need get right of entry to to each different's implementation in ways that the rest of the sector should not be allowed to have. In other phrases, they assist hold non-public things personal. For instance, it is able to be suitable for sophistication DatabaseCursor to have extra privilege to the internals of sophistication Database than major() has.

Q23. If I Don't Specify Either Public Or Private Sections In A Class, What Is The Default?

In a class, all individuals are personal by default if neither public nor non-public sections are declared.

Q24. What Is Encapsulation?

Packaging an object’s variables within its strategies is referred to as encapsulation.

Q25. I Would Like To Use C++ Fstreams On A File Opened In Binary Mode, How Is This Done?

Use ios::binary because the open mode for the file: 

#consist of 

ifstream binfile; 

binfile.Open("myfile.Bin", ios::binary);

Q26. When Linking C Or Assembly Language Modules With C++ Modules I Get Undefined Symbol Errors At Link Time. It Appears That None Of The C Or Assembly Public Symbols Can Be Found.?

C++ is a strongly typed language. In order to help the language to its fullest, Turbo C++ need to connect records to the symbols generated for feature names and variables. When this is achieved, the symbol will not suit the standard C style function call. In order to link successfully, the compiler must be notified that the image is asserted in an external module with out type data tacked on to the symbol. This is done by prototyping the feature as kind extern "C". Here is a brief instance: extern "C" int normal_c_func( waft, int, char ); // call not altered void cplusplus_function( int ); // call altered .

Q27. What Are The Advantages Of Inheritance?

It permits code reusability.

Reusability saves time in program improvement.

It encourages the reuse of tested and debugged extremely good software program, therefore decreasing hassle after a machine will become practical.

Q28. Are The Standard Library I/o Functions Still Available For Use With The C++ Iostreams Library?

Yes, using 

#encompass 

features together with printf() and scanf() will stay available. However, the usage of them along side stream oriented capabilities can lead to unpredictable behaviour.

Q29. What Is A Friend Member Function?

Declaring a friend offers non-individuals of a category get entry to to the personal members of a category.

Q30. Classes With Static Data Members Are Getting Linker Errors ("undefined").?

This code is constructed into Turbo C++ 1.Zero but now not in model three.@In the 1.0 compiler, static individuals without definitions have been given a default fee of @This default definition will no longer be made inside the compiler. The programmer should now give an specific definition for every static member.

Here is a quick example: 

class A 

 

static int i; 

; 

A linker mistakes saying that A::i isn't described will result except the source additionally incorporates a line along with: 

int A::i = 1;

Q31. What Are Inline Functions? What Are Their Advantages? How Are They Declared?

An inline feature is a characteristic which receives textually inserted by using the compiler, similar to macros. The benefit is that execution time is shortened because linker overhead is minimized. They are declared through the usage of the inline keyword when the feature is declared: 

inline void func(void)  cout << "printing inline characteristic n";  

or with the aid of which includes the function statement and code body inside a class: 

magnificence test 

 

television public: 

void func(void)  cout << "inline characteristic inside a category.N" 

;

Q32. What Do You Mean By Inheritance?

Inheritance is the procedure of making new lessons, known as derived classes, from present training or base lessons. The derived magnificence inherits all the talents of the bottom elegance, however can add elaborations and refinements of its very own.

Q33. Will The Following Two Functions Be Overloaded By The Compiler, Or Will The Compiler Flag It As An Error? Why? Void Test( Int X, Double Y); & Int Test( Int A, Double B).

The compiler will flag this as a redeclaration mistakes because neither return types nor argument names are considered while figuring out unique signatures for overloading capabilities. Only range and form of arguments are taken into consideration.

Q34. What Is An Object?

Object is a software program bundle of variables and related methods. Objects have country and behavior.

Q35. In C++, Given Two Variables Of The Same Name, One Local And One Global, How Do I Access The Global Instance Within The Local Scope?

Use the scope (::) operator. 

Int x = 10; 

for(int x=zero; x < ::x; x++) 

 

cout << "Loop # " << x << "n"; // This will loop 10 times 

Q36. 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 thefunction is called. If done carefully, this can improve the application'sperformance in exchange for increased compile time and possibly (but not always) an increase in the size of the generated binary executables.

Q37. What Is Public, Protected, Private?

Public, protected and private are three access specifiers 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.

Q38. What Is Function Overloading And Operator Overloading?

Student Resources 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).

Q39. Why Garbage Collection?

Since C++ does not provide automatic garbage collection like some other languages, smart pointers can be used for that purpose. The simplest garbage collection scheme is reference counting or reference linking, but it is quite possible to implement more sophisticated garbage collection schemes with smart pointers.

Q40. I Want To Use _new_handler And Set_new_handler.

Turbo C++ supports _new_handler and set_new_handler.

The type of _new_handler is as follows:

typedef void (*vfp)(void); 

vfp _new_handler; 

vfp set_new_handler( vfp );

Q41. What Is A Scope Resolution Operator?

A scope resolution operator (::), can be used to define the member functions of a class outside the class.

Q42. Why Does A Binary Member Function Only Accept A Single Argument?

The first argument is defined implicitly.

Q43. 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.

Class: Class is a successor of Structure. By default all the members inside the class are private.

Q44. 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. Does c++ support multilevel and multiple inheritance.

Q45. What Is The "this" Pointer?

"this" is a local variable in the body of a non-static member function. It is a pointer to the object for which the function was invoked. It cannot be used outside of a class member function body.

Q46. I Have Declared A Derived Class From A Base Class, But I Can't Access Any Of The Base Class Members With The Derived Class Function.?

Derived classes DO NOT get access to private members of a base class. In order to access members of a base class, the base class members must be declared as either public or protected. If they are public, then any portion of the program can access them. If they are protected, they are accessible by the class members, friends, and any derived classes.

Q47. How Can I Get At The Dos File Handle Associated With My Iostream?

Using a combination of member functions fd() and rdbuf() you can get at the file handle. 

#include 

#define fstrno(s) (((s).Rdbuf())->fd()) 

ifstream take a look at("test.Txt"); 

cout << "deal with is " << fstrno(check) << 'n';