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1、【精品文档】如有侵权，请联系网站删除，仅供学习与交流常见英文面试笔试题目.精品文档.C/C+ Programming interview questions and answers By Satish Shetty, July 14th, 2004What is encapsulation?Containing and hiding information about an object, such as internal data structures and code. Encapsulation isolates the internal complexity of an objects
2、 operation from the rest of the application. For example, a client component asking for net revenue from a business object need not know the datas origin.What is inheritance?Inheritance allows one class to reuse the state and behavior of another class. The derived class inherits the properties and m
3、ethod implementations of the base class and extends it by overriding methods and adding additional properties and methods.What is Polymorphism?Polymorphism allows a client to treat different objects in the same way even if they were created from different classes and exhibit different behaviors.You
4、can use implementation inheritance to achieve polymorphism in languages such as C+ and Java.Base class objects pointer can invoke methods in derived class objects.You can also achieve polymorphism in C+ by function overloading and operator overloading.What is constructor or ctor?Constructor creates
5、an object and initializes it. It also creates vtable for virtual functions. It is different from other methods in a class.What is destructor?Destructor usually deletes any extra resources allocated by the object. What is default constructor?Constructor with no arguments or all the arguments has defa
6、ult values.What is copy constructor?Constructor which initializes the its object member variables ( by shallow copying) with another object of the same class. If you dont implement one in your class then compiler implements one for you.for example:Boo Obj1(10); / calling Boo constructorBoo Obj2(Obj1
7、); / calling boo copy constructorBoo Obj2 = Obj1;/ calling boo copy constructorWhen are copy constructors called? Copy constructors are called in following cases: a) when a function returns an object of that class by valueb) when the object of that class is passed by value as an argument to a functi
8、onc) when you construct an object based on another object of the same classd) When compiler generates a temporary objectWhat is assignment operator? Default assignment operator handles assigning one object to another of the same class. Member to member copy (shallow copy)What are all the implicit me
9、mber functions of the class? Or what are all the functions which compiler implements for us if we dont define one.?default ctorcopy ctorassignment operatordefault destructoraddress operatorWhat is conversion constructor?constructor with a single argument makes that constructor as conversion ctor and
10、 it can be used for type conversion.for example:class Boo public: Boo( int i );Boo BooObject = 10 ; / assigning int 10 Boo objectWhat is conversion operator?class can have a public method for specific data type conversions.for example:class Boo double value; public: Boo(int i ) operator double() ret
11、urn value; ;Boo BooObject;double i = BooObject; / assigning object to variable i of type double. now conversion operator gets called to assign the value.What is diff between malloc()/free() and new/delete?malloc allocates memory for object in heap but doesnt invoke objects constructor to initiallize
12、 the object.new allocates memory and also invokes constructor to initialize the object.malloc() and free() do not support object semantics Does not construct and destruct objects string * ptr = (string *)(malloc (sizeof(string)Are not safe Does not calculate the size of the objects that it construct
13、 Returns a pointer to void int *p = (int *) (malloc(sizeof(int);int *p = new int;Are not extensible new and delete can be overloaded in a class delete first calls the objects termination routine (i.e. its destructor) and then releases the space the object occupied on the heap memory. If an array of
14、objects was created using new, then delete must be told that it is dealing with an array by preceding the name with an empty :-Int_t *my_ints = new Int_t10;delete my_ints;what is the diff between new and operator new ?operator new works like malloc.What is difference between template and macro?There
15、 is no way for the compiler to verify that the macro parameters are of compatible types. The macro is expanded without any special type checking.If macro parameter has a postincremented variable ( like c+ ), the increment is performed two times.Because macros are expanded by the preprocessor, compil
16、er error messages will refer to the expanded macro, rather than the macro definition itself. Also, the macro will show up in expanded form during debugging.for example:Macro:#define min(i, j) (i j ? i : j)template:template T min (T i, T j) return i j ? i : j;What are C+ storage classes?autoregisters
17、taticexternauto: the default. Variables are automatically created and initialized when they are defined and are destroyed at the end of the block containing their definition. They are not visible outside that blockregister: a type of auto variable. a suggestion to the compiler to use a CPU register
18、for performancestatic: a variable that is known only in the function that contains its definition but is never destroyed and retains its value between calls to that function. It exists from the time the program begins executionextern: a static variable whose definition and placement is determined wh
19、en all object and library modules are combined (linked) to form the executable code file. It can be visible outside the file where it is defined.What are storage qualifiers in C+ ?They are.constvolatilemutableConstkeyword indicates that memory once initialized, should not be altered by a program.vol
20、atilekeyword indicates that the value in the memory location can be altered even though nothing in the programcode modifies the contents. for example if you have a pointer to hardware location that contains the time, where hardware changes the value of this pointer variable and not the program. The
21、intent of this keyword to improve the optimization ability of the compiler. mutable keyword indicates that particular member of a structure or class can be altered even if a particular structure variable, class, or class member function is constant.struct datachar name80;mutable double salary;const
22、data MyStruct = Satish Shetty, 1000 ; /initlized by complierstrcpy ( MyStruct.name, Shilpa Shetty); / compiler errorMyStruct.salaray = 2000 ; / complier is happy allowedWhat is reference ?reference is a name that acts as an alias, or alternative name, for a previously defined variable or an object.p
23、repending variable with & symbol makes it as reference.for example:int a;int &b = a; What is passing by reference?Method of passing arguments to a function which takes parameter of type reference.for example:void swap( int & x, int & y ) int temp = x; x = y; y = temp;int a=2, b=3;swap( a, b );Basica
24、lly, inside the function there wont be any copy of the arguments x and y instead they refer to original variables a and b. so no extra memory needed to pass arguments and it is more efficient. When do use const reference arguments in function?a) Using const protects you against programming errors th
25、at inadvertently alter data.b) Using const allows function to process both const and non-const actual arguments, while a function without const in the prototype can only accept non constant arguments.c) Using a const reference allows the function to generate and use a temporary variable appropriatel
26、y. When are temporary variables created by C+ compiler?Provided that function parameter is a const reference, compiler generates temporary variable in following 2 ways.a) The actual argument is the correct type, but it isnt Lvaluedouble Cube(const double & num) num = num * num * num; return num;doub
27、le temp = 2.0;double value = cube(3.0 + temp); / argument is a expression and not a Lvalue;b) The actual argument is of the wrong type, but of a type that can be converted to the correct typelong temp = 3L;double value = cuberoot ( temp); / long to double conversion What is virtual function?When der
28、ived class overrides the base class method by redefining the same function, then if client wants to access redefined the method from derived class through a pointer from base class object, then you must define this function in base class as virtual function.class parent void Show() cout im parent en
29、dl;class child: public parent void Show() cout im child show() / calls parent-show() i now we goto virtual world.class parent virtual void Show() cout im parent endl;class child: public parent void Show() cout im child show() / calls child-show() What is pure virtual function? or what is abstract cl
30、ass?When you define only function prototype in a base class without implementation and do the complete implementation in derived class. This base class is called abstract class and client wont able to instantiate an object using this base class.You can make a pure virtual function or abstract class
31、this way.class Boovoid foo() = 0;Boo MyBoo; / compilation error What is Memory alignment?The term alignment primarily means the tendency of an address pointer value to be a multiple of some power of two. So a pointer with two byte alignment has a zero in the least significant bit. And a pointer with
32、 four byte alignment has a zero in both the two least significant bits. And so on. More alignment means a longer sequence of zero bits in the lowest bits of a pointer.What problem does the namespace feature solve?Multiple providers of libraries might use common global identifiers causing a name coll
33、ision when an application tries to link with two or more such libraries. The namespace feature surrounds a librarys external declarations with a unique namespace that eliminates the potential for those collisions.namespace identifier namespace-body A namespace declaration identifies and assigns a na
34、me to a declarative region.The identifier in a namespace declaration must be unique in the declarative region in which it is used. The identifier is the name of the namespace and is used to reference its members.What is the use of using declaration?A using declaration makes it possible to use a name
35、 from a namespace without the scope operator. What is an Iterator class?A class that is used to traverse through the objects maintained by a container class. There are five categories of iterators: input iterators, output iterators, forward iterators, bidirectional iterators, random access. An itera
36、tor is an entity that gives access to the contents of a container object without violating encapsulation constraints. Access to the contents is granted on a one-at-a-time basis in order. The order can be storage order (as in lists and queues) or some arbitrary order (as in array indices) or accordin
37、g to some ordering relation (as in an ordered binary tree). The iterator is a construct, which provides an interface that, when called, yields either the next element in the container, or some value denoting the fact that there are no more elements to examine. Iterators hide the details of access to
38、 and update of the elements of a container class. Something like a pointer. 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
39、 the address of the memory block after it is freed.What do you mean by Stack unwinding?It is a process during exception handling when the destructor is called for all local objects in the stack between the place where the exception was thrown and where it is caught.Name the operators that cannot be
40、overloaded?sizeof, ., .*, .-, :, ?: What is a container class? What are the types of container classes?A container class is a class that is used to hold objects in memory or external storage. A container class acts as a generic holder. A container class has a predefined behavior and a well-known int
41、erface. A container class is a supporting class whose purpose is to hide the topology used for maintaining the list of objects in memory. When a container class contains a group of mixed objects, the container is called a heterogeneous container; when the container is holding a group of objects that
42、 are all the same, the container is called a homogeneous container. What is inline function?The _inline keyword tells the compiler to substitute the code within the function definition for every instance of a function call. However, substitution occurs only at the compilers discretion. For example,
43、the compiler does not inline a function if its address is taken or if it is too large to inline. What is overloading?With the C+ language, you can overload functions and operators. Overloading is the practice of supplying more than one definition for a given function name in the same scope.- Any two
44、 functions in a set of overloaded functions must have different argument lists.- Overloading functions with argument lists of the same types, based on return type alone, is an error. What is Overriding?To override a method, a subclass of the class that originally declared the method must declare a m
45、ethod with the same name, return type (or a subclass of that return type), and same parameter list.The definition of the method overriding is: Must have same method name. Must have same data type. Must have same argument list. Overriding a method means that replacing a method functionality in child
46、class. To imply overriding functionality we need parent and child classes. In the child class you define the same method signature as one defined in the parent class.What is this pointer?The this pointer is a pointer accessible only within the member functions of a class, struct, or union type. It points to the object for which the member function is called. Static member functions do not have a this pointer.When a nonstatic member function is called for an object, the address of the object is passed as a hidden argum