C Language Interview Question and Answers 1.What is C language? C is a programming language developed at AT & T's Bell Laboratories of USA in 1972.The C programming language is a standardized programming language developed in the early 1970s by Ken Thompson and Dennis Ritchie for use on the UNIX operating system. It has since spread to many other operating systems, and is one of the most widely used programming languages 2.What are the types of constants in c? C constants can ba divided into two categories : Primary constants Secondary constants 3.What are the types of C intructions? Now that we have written a few programs let us look at the instructions that we used in these programs. There are basically three types of instructions in C : Type Declaration Instruction Arithmetic Instruction Control Instruction 4.What is a pointer? Pointers are variables which stores the address of another variable. That variable may be a scalar (including another pointer), or an aggregate (array or structure). The pointed-to object may be part of a larger object, such as a field of a structure or an element in an array. 5.What is the difference between arrays and pointers? Pointers are used to manipulate data using the address. Pointers use • operator to access the data pointed to by them.Arrays is a collection of similar datatype. Array use subscripted variables to access and manipulate data. Array variables can be Equivalently written using pointer expression. 6.What is “this”s 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. 7.What are the uses of a pointer? Pointer is used in the following cases It is used to access array elements. It is used for dynamic memory allocation. It is used in Call by reference. It is used in data structures like trees, graph, linked list etc. 8.What is the purpose of main() function? The function main() invokes other functions within it.It is the first function to be called when the program starts execution. It is the starting function. It returns an int value to the environment that called the program. Recursive call is allowed for main( ) also. It is a user-defined function. 9.What are the different storage classes in C? There are four types of storage classes. Automatic Extern Regiter Static 10.Define inheritance? Inheritance is the process by which objects of one class acquire properties of objects of another class. 11.Define destuctors? A destructor is called for a class object when that object passes out of scope or is explicitly deleted.A destructors as the name implies is used to destroy the objects that have been created by a constructors.Like a constructor , the destructor is a member function whose name is the same as the class name but is precided by a tilde. 12.What is a structure? Structure constitutes a super data type which represents several different data types in a single unit. A structure can be initialized if it is static or global. 13.What is message passing? An object oriented program consists of a set of objects that communicate with each other. Message passing involves specifying the name of the object, the name of the function and the information to be sent. 14.Define Constructors? A constructor is a member function with the same name as its class. The constructor is invoked whenever an object of its associated class is created.It is called constructor because it constructs the values of data members of the class. 15.What is the use of default constructor? A constructors that accepts no parameters is called the default constructor.If no user-defined constructor exists for a class A and one is needed, the compiler implicitly declares a default parameterless constructor A::A(). This constructor is an inline public member of its class. The compiler will implicitly define A::A() when the compiler uses this constructor to create an object of type A. The constructor will have no constructor initializer and a null body. 16.What is a macro? Macros are the identifiers that represent statements or expressions. To associate meaningful identifiers with constants, keywords, and statements or expressions. 17.What is arrays? Array is a variable that hold multiple elements which has the same data type. 18.What is the difference between #include‹ › and #include “ ”? #include‹ › ----> Specifically used for built in header files.#include “ ” ----> Specifically used for used for user defined/created n header file. 19.What are the advantages of the functions? It reduces the Complexity in a program by reducing the code. Function are easily understanding and reliability and execution is faster. It also reduces the Time to run a program.In other way,Its directly proportional to Complexity. Its easy to find-out the errors due to the blocks made as function definition outside the main function. 20.How do declare an array? We can declare an array by specify its data type, name and the number of elements the array holds between square brackets immediately following the array name.syntax : data_type array_name[size]; 21.What are the differences between structures and union? A structure variable contains each of the named members, and its size is large enough to hold all the members. Structure elements are of same size. A Union contains one of the named members at a given time and is large enough to hold the largest member. Union element can be of different sizes. 22.What is the difference between arrays and pointers? Array is collection of similar datatype. it is a static memory allocation means we can not increment and decrement the arry size once we allocated. and we can not increment the base address, reassign address. Pointer is a dynamic memory allocation. we can allocate the size as we want, assigning into another variable and base address incrementation is allowed. 23.What is dynamic binding? Dynamic binding (also known as late binding) means that the code associated with a given procedure call is not known until the time of the call at run time.It is associated with polymorphism and inheritance. 24.what is an abstract base class? An abstract class is a class that is designed to be specifically used as a base class. An abstract class contains at least one pure virtual function. 25.What is the difference between class and structure? 26.What is static identifier? A file- scope variable that is declared static is visible only to functions within that file. A function -scope or block-scope variable that is declared as static is visible only within that scope.Further more, static variables only have a single instance. In the case of function- or block-scope variables, this means that the variable is not “automatic” and thus retains its value across function invocations. 27.What is a dynamic constructor? The constructor can also be used to allocate memory while creating objects. Allocation of memory to objects at the time of their construction is known as dynamic construction of objects.The memory is allocated with the help of the new operator. 28.What is the difference between an Array and a List? The main difference between an array and a list is how they internally store the data. whereas Array is collection of homogeneous elements. List is collection of heterogeneous elements. 29.What are the advantages of inheritance? Code reusability Saves time in program development. 30.what is difference between function overloading and operator overloading? A function is overloaded when same name is given to different function. While overloading a function, the return type of the functions need to be the same. 31.Define a class? A class represents description of objects that share same attributes and actions. It defines the characteristics of the objects such as attributes and actions or behaviors. It is the blue print that describes objects. 32.What is the term Polymorphism? To override a method, a subclass of the class that originally declared the method must declare a method with the same name, return type (or a subclass of that return type), and same parameter list. 33.What is Overriding? The main difference between an array and a list is how they internally store the data. whereas Array is collection of homogeneous elements. List is collection of heterogeneous elements. 34.What is encapsulation? Containing and hiding information about an object, such as internal data structures and code. Encapsulation isolates the internal complexity of an object’s operation from the rest of the application. 35.What is a pointer variable? A pointer variable is a variable that may contain the address of another variable or any valid address in the memory. 36.What is the difference between a string copy (strcpy) and a memory copy (memcpy)? The strcpy() function is designed to work exclusively with strings. It copies each byte of the source string to the destination string and stops when the terminating null character () has been moved. On the other hand, the memcpy() function is designed to work with any type of data. Because not all data ends with a null character, you must provide the memcpy() function with the number of bytes you want to copy from the source to the destination. 37.What is the difference between a NULL Pointer and a NULL Macro? Null pointer is a pointer that is pointing nothing while NULL macro will used for replacing 0 in program as #define NULL 0 . 38.What is the difference between const char*p and char const* p? const char*p - p is pointer to the constant character. i.e value in that address location is constant. const char* const p - p is the constant pointer which points to the constant string, both value and address are constants. 39.What is the purpose of realloc()? Realloc(ptr,n) function uses two arguments. The first argument ptr is a pointer to a block of memory for which the size is to be altered. The second argument n specifies the new size.The size may be increased or decreased. 40.What is a pointer value and address? A pointer value is a data object that refers to a memory location. Each memory location is numbered in the memory. The number attached to a memory location is called the address of the location. 41.What is the use of typedef? The typedef help in easier modification when the programs are ported to another machine.A descriptive new name given to the existing data type may be easier to understand the code. 42.What are the differences between new and malloc? New initializes the allocated memory by calling the constructor. Memory allocated with new should be released with delete. Malloc allocates uninitialized memory. The allocated memory has to be released with free.new automatically calls the constructor while malloc(dosen’t) 43.What is the difference between strdup and strcpy? Both copy a string. strcpy wants a buffer to copy into. strdup allocates a buffer using malloc(). Unlike strcpy(), strdup() is not specified by ANSI. 44.What is this pointer? It is a pointer that points to the current object. This can be used to access the members of the current object with the help of the arrow operator. 45.What is friend function? The function declaration should be preceded by the keyword friend.The function definitions does not use either the keyword or the scope operator ::. The functions that are declared with the keyword friend as friend function.Thus, a friend function is an ordinary function or a member of another class. 46.What is recursion? A recursion function is one which calls itself either directly or indirectly it must halt at a definite point to avoid infinite recursion. 47.What are the characteristics of arrays in C? An array holds elements that have the same data type. Array elements are stored in subsequent memory locations Two-dimensional array elements are stored row by row in subsequent memory locations. Array name represents the address of the starting element 48.What is the differentiate between for loop and a while loop? What are it uses? For executing a set of statements fixed number of times we use for loop while when the number of iterations to be performed is not known in advance we use while loop. 49.What is the difference between printf(...) and sprintf(...)? printf(....) -------------> is standard output statement sprintf(......)-----------> is formatted output statement. 50.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.Explicit constructors are simply constructors that cannot take part in an implicit conversion. By default, the members ot structures are public while that tor class is private. structures doesn’t provide something like data hiding which is provided by the classes. structures contains only data while class bind both data and member functions.

• C Language Interview Question and Answers
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• 1.	What is C language?
  	C is a programming language developed at AT & T's Bell Laboratories of USA in 1972.The C programming language is a standardized programming language developed in the early 1970s by Ken Thompson and Dennis Ritchie for use on the UNIX operating system. It has since spread to many other operating systems, and is one of the most widely used programming languages

  2.	What are the types of constants in c?
  	C constants can ba divided into two categories : Primary constants Secondary constants

  3.	What are the types of C intructions?
  	Now that we have written a few programs let us look at the instructions that we used in these programs. There are basically three types of instructions in C : Type Declaration Instruction Arithmetic Instruction Control Instruction

  4.	What is a pointer?
  	Pointers are variables which stores the address of another variable. That variable may be a scalar (including another pointer), or an aggregate (array or structure). The pointed-to object may be part of a larger object, such as a field of a structure or an element in an array.

  5.

  What is the difference between arrays and pointers?

  Pointers are used to manipulate data using the address. Pointers use • operator to access the data pointed to by them. Arrays is a collection of similar datatype. Array use subscripted variables to access and manipulate data. Array variables can be Equivalently written using pointer expression. 6. What is “this”s 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. 7. What are the uses of a pointer? Pointer is used in the following cases It is used to access array elements. It is used for dynamic memory allocation. It is used in Call by reference. It is used in data structures like trees, graph, linked list etc. 8. What is the purpose of main() function? The function main() invokes other functions within it.It is the first function to be called when the program starts execution. It is the starting function. It returns an int value to the environment that called the program. Recursive call is allowed for main( ) also. It is a user-defined function. 9. What are the different storage classes in C? There are four types of storage classes. Automatic Extern Regiter Static 10. Define inheritance? Inheritance is the process by which objects of one class acquire properties of objects of another class. 11. Define destuctors? A destructor is called for a class object when that object passes out of scope or is explicitly deleted.A destructors as the name implies is used to destroy the objects that have been created by a constructors.Like a constructor , the destructor is a member function whose name is the same as the class name but is precided by a tilde. 12. What is a structure? Structure constitutes a super data type which represents several different data types in a single unit. A structure can be initialized if it is static or global. 13. What is message passing? An object oriented program consists of a set of objects that communicate with each other. Message passing involves specifying the name of the object, the name of the function and the information to be sent. 14. Define Constructors? A constructor is a member function with the same name as its class. The constructor is invoked whenever an object of its associated class is created.It is called constructor because it constructs the values of data members of the class. 15. What is the use of default constructor? A constructors that accepts no parameters is called the default constructor.If no user-defined constructor exists for a class A and one is needed, the compiler implicitly declares a default parameterless constructor A::A(). This constructor is an inline public member of its class. The compiler will implicitly define A::A() when the compiler uses this constructor to create an object of type A. The constructor will have no constructor initializer and a null body. 16. What is a macro? Macros are the identifiers that represent statements or expressions. To associate meaningful identifiers with constants, keywords, and statements or expressions. 17. What is arrays? Array is a variable that hold multiple elements which has the same data type. 18. What is the difference between #include‹ › and #include “ ”? #include‹ › ----> Specifically used for built in header files. #include “ ” ----> Specifically used for used for user defined/created n header file. 19. What are the advantages of the functions? It reduces the Complexity in a program by reducing the code. Function are easily understanding and reliability and execution is faster. It also reduces the Time to run a program.In other way,Its directly proportional to Complexity. Its easy to find-out the errors due to the blocks made as function definition outside the main function. 20. How do declare an array? We can declare an array by specify its data type, name and the number of elements the array holds between square brackets immediately following the array name. syntax :  data_type array_name[size]; 21. What are the differences between structures and union? A structure variable contains each of the named members, and its size is large enough to hold all the members. Structure elements are of same size. A Union contains one of the named members at a given time and is large enough to hold the largest member. Union element can be of different sizes. 22. What is the difference between arrays and pointers? Array is collection of similar datatype. it is a static memory allocation means we can not increment and decrement the arry size once we allocated. and we can not increment the base address, reassign address. Pointer is a dynamic memory allocation. we can allocate the size as we want, assigning into another variable and base address incrementation is allowed. 23. What is dynamic binding? Dynamic binding (also known as late binding) means that the code associated with a given procedure call is not known until the time of the call at run time.It is associated with polymorphism and inheritance. 24. what is an abstract base class? An abstract class is a class that is designed to be specifically used as a base class. An abstract class contains at least one pure virtual function. 25. What is the difference between class and structure? 26. What is static identifier? A file- scope variable that is declared static is visible only to functions within that file. A function -scope or block-scope variable that is declared as static is visible only within that scope.Further more, static variables only have a single instance. In the case of function- or block-scope variables, this means that the variable is not “automatic” and thus retains its value across function invocations. 27. What is a dynamic constructor? The constructor can also be used to allocate memory while creating objects. Allocation of memory to objects at the time of their construction is known as dynamic construction of objects.The memory is allocated with the help of the new operator. 28. What is the difference between an Array and a List? The main difference between an array and a list is how they internally store the data. whereas Array is collection of homogeneous elements. List is collection of heterogeneous elements. 29. What are the advantages of inheritance? Code reusability Saves time in program development. 30. what is difference between function overloading and operator overloading? A function is overloaded when same name is given to different function. While overloading a function, the return type of the functions need to be the same. 31. Define a class? A class represents description of objects that share same attributes and actions. It defines the characteristics of the objects such as attributes and actions or behaviors. It is the blue print that describes objects. 32. What is the term Polymorphism? To override a method, a subclass of the class that originally declared the method must declare a method with the same name, return type (or a subclass of that return type), and same parameter list. 33. What is Overriding? The main difference between an array and a list is how they internally store the data. whereas Array is collection of homogeneous elements. List is collection of heterogeneous elements. 34. What is encapsulation? Containing and hiding information about an object, such as internal data structures and code. Encapsulation isolates the internal complexity of an object’s operation from the rest of the application. 35. What is a pointer variable? A pointer variable is a variable that may contain the address of another variable or any valid address in the memory. 36. What is the difference between a string copy (strcpy) and a memory copy (memcpy)? The strcpy() function is designed to work exclusively with strings. It copies each byte of the source string to the destination string and stops when the terminating null character () has been moved. On the other hand, the memcpy() function is designed to work with any type of data. Because not all data ends with a null character, you must provide the memcpy() function with the number of bytes you want to copy from the source to the destination. 37. What is the difference between a NULL Pointer and a NULL Macro? Null pointer is a pointer that is pointing nothing while NULL macro will used for replacing 0 in program as #define NULL 0 . 38. What is the difference between const char*p and char const* p? const char*p - p is pointer to the constant character. i.e value in that address location is constant. const char* const p - p is the constant pointer which points to the constant string, both value and address are constants. 39. What is the purpose of realloc()? Realloc(ptr,n) function uses two arguments. The first argument ptr is a pointer to a block of memory for which the size is to be altered. The second argument n specifies the new size.The size may be increased or decreased. 40. What is a pointer value and address? A pointer value is a data object that refers to a memory location. Each memory location is numbered in the memory. The number attached to a memory location is called the address of the location. 41. What is the use of typedef? The typedef help in easier modification when the programs are ported to another machine.A descriptive new name given to the existing data type may be easier to understand the code. 42. What are the differences between new and malloc? New initializes the allocated memory by calling the constructor. Memory allocated with new should be released with delete. Malloc allocates uninitialized memory. The allocated memory has to be released with free.new automatically calls the constructor while malloc(dosen’t) 43. What is the difference between strdup and strcpy? Both copy a string. strcpy wants a buffer to copy into. strdup allocates a buffer using malloc(). Unlike strcpy(), strdup() is not specified by ANSI. 44. What is this pointer? It is a pointer that points to the current object. This can be used to access the members of the current object with the help of the arrow operator. 45. What is friend function? The function declaration should be preceded by the keyword friend.The function definitions does not use either the keyword or the scope operator ::. The functions that are declared with the keyword friend as friend function.Thus, a friend function is an ordinary function or a member of another class. 46. What is recursion? A recursion function is one which calls itself either directly or indirectly it must halt at a definite point to avoid infinite recursion. 47. What are the characteristics of arrays in C? An array holds elements that have the same data type. Array elements are stored in subsequent memory locations Two-dimensional array elements are stored row by row in subsequent memory locations. Array name represents the address of the starting element 48. What is the differentiate between for loop and a while loop? What are it uses? For executing a set of statements fixed number of times we use for loop while when the number of iterations to be performed is not known in advance we use while loop. 49. What is the difference between printf(...) and sprintf(...)? printf(....) -------------> is standard output statement sprintf(......)-----------> is formatted output statement. 50. 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.Explicit constructors are simply constructors that cannot take part in an implicit conversion. By default, the members ot structures are public while that tor class is private. structures doesn’t provide something like data hiding which is provided by the classes. structures contains only data while class bind both data and member functions.

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