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CPlusPlus Interview Questions Answers

Question 1 : What problems might the following macro bring to the application?

Answer 1 : #define sq(x) x*x

Question 2 : What’s the output of the following program? Why?

Answer 2 : #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)

Question 3 : Write a program that ask for user input from 5 to 9 then calculate the average

Answer 3 : #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; }

Question 4 : Count Number of characters using Pointers?

Answer 4 : #include<iostream.h> void main() { int Char_Count(char *get_string); char *strcount "THIS IS A STRING"; int int_word_count Char_Count(strcount); cout<<"word count is "<<int_word_count; } int Char_Count(char *get_string) { int count 0; if (get_string ! NULL) { for (;*(get_string+count) ! ' ';++count); } return count; }  

Question 5 : What are the advantages of inheritance?

Answer 5 : • 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.

Question 6 : What is polymorphism? Explain with an example?

Answer 6 : "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.

Question 7 : What are the conditions that have to be met for a condition to be an invariant of the class?

Answer 7 : * The condition should hold at the end of every constructor. * The condition should hold at the end of every mutator (non-const) operation.

Question 8 : Explain differences between eg. new() and malloc()

Answer 8 : 1. 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()] 2. 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.

Question 9 : What is the difference between an ARRAY and a LIST?

Answer 9 : 1. 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. 2. 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++; }

Question 10 : What are the advantages and disadvantages of B-star trees over Binary trees?

Answer 10 : 1. B-star trees have better data structure and are faster in search than Binary trees, but it’s harder to write codes for B-start trees. 2. The major difference between B-tree and binary tres is that B-tree is a external data structure and binary tree is a main memory data structure. The computational complexity of binary tree is counted by the number of comparison operations at each node, while the computational complexity of B-tree is determined by the disk I/O, that is, the number of node that will be loaded from disk to main memory. The comparision of the different values in one node is not counted.

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