C and C++ Interview Questions and Answers
C and C++ programming languages are in demand in industries for operating system development and application development. Here are the popular and frequently asked top 20 C and C++ interview questions and answers to help you ace the technical rounds.
C and C++ Interview Questions and Answers for Freshers
1. What is C programming?
C is the pioneering programming language that has both characteristics of assembly-level (low-level) and higher-level languages. It is also known as middle-level language and it is used to write an operating system and menu-driven consumer billing applications.
2. What are the features of C programming?
The following are the features of C Programming.
- Simple and Efficient
- Portable and Machine-Dependent
- Middle-level programming characteristics
- Structured programming language
- Function-rich libraries
- Dynamic memory management system
- Super-fast and extensible
- Pointers can be used in C.
3. Define a built-in function in C
The system provides built-in functions, or library functions, to enable developers to do common activities using pre-defined tasks.
For instance, If we want to print output into the terminal, we can use printf() in C.
The most popular built-in functions in C are scanf(), printf(), strcpy, strlwr, strcmp, strlen, strcat, and so on.
4. Define Preprocessor
A preprocessor is a software application that processes a source file before compilation. It includes header files, conditional compilation, line control, and macro expansion.
5. Define Pointer in C
A pointer is a variable that stores the address of another variable. If the value of the variable is stored in a normal variable, then the address of the variable is stored in a pointer variable.
6. Explain the various types of decision control statements
The control statements are used to execute or convert the control from one portion of the program to another following the condition. The statements written in a program are implemented sequentially from top to bottom.
- If – else statement
- Normal if-else statement
- Else-if statement
- Nested if-else statement
- Switch statement
7. What are the real-world applications that can be developed using C++?
C++ is the powerful programming language used to develop the following kinds of applications
- Operating System
- GUI Based Applications
- Distributed Systems
- Database Software
- Banking Applications
- Advanced Computations and Graphics
- Embedded Systems
8. What are the various data types used in C++?
There are 4 major data types used in C++ and they are
- The primitive data type is a basic datatype like char, short, int, long, float, bool, or double.
- Derived data types include arrays, pointers, and so on.
- Enumeration data types like Enum
- User-defined data types, like structure or class
C and C++ Interview Questions and Answers for Experienced
9. Define recursion in C
Recursion is the thing that happens when a function in C calls a copy of itself. In simple terms, when a function calls itself, it is known as recursion and the function is known as a recursive function.
Syntax
void do_recursion()
{
… .. …
do_recursion();
… .. …]
}
int main()
{
… .. …
do_recursion();
… .. …
}
10. Differentiate global int and static int declaration with example
The scope is only the difference between static and global integers. The global_temp is a global variable that is known to everything inside the program and it will be visible when we add “extern int global_temp;” in the source file.
#include <stdio.h>
int my_global_var = 0;
int
main(void)
{
printf(“%d\n”, my_global_var);
return 0;
}
A static variable has a local scope that doesn’t allocate the variable in the stack segment of the memory. It will have less than global scope and it resides in the .bss segment of the combined binary.
#include <stdio.h>
int
myfunc(int val)
{
static int my_static_var = 0;
my_static_var += val;
return my_static_var;
}
int
main(void)
{
int myval;
myval = myfunc(1);
printf(“first call %d\n”, myval);
myval = myfunc(10);
printf(“second call %d\n”, myval);
return 0;
}
11. Define typecasting in C
Typecasting is the process that converts a variable from one data type to another and if we want to store the large type value to an int type, then we can convert the data type into another data type explicitly.
Syntax
int x;
for(x = 12; x<=54; x++)
{
printf(“%c”, (char) x); /*Explicit casting from int to char*/
}
12. Explain dangling pointers
The dangling pointer points to a memory that has been freed already and the storage will no longer be allocated. When we try to access it, that might lead to a segmentation fault. To end this, we can use a dangling pointer.
#include<stdio.h>
#include<string.h>
char *func()
{
char str[10];
strcpy(str,”Hello!”);
return(str);
}
Here, the local variable will return an address that can be scoped by the time control that was returned to the calling function.
*c = malloc (sizeof(int));
free(c);
*c = 3;
13. Write a program to remove duplicates in an array
#include <stdio.h>
int main()
{
int n, a[100], b[100], calc = 0, i, j,count;
printf(“Enter no. of elements in array.n”);
scanf(“%d”, &n);
printf(“Enter %d integers”, n);
for (i = 0; i < n; i++)
scanf(“%d”, &a[i]);
for (i = 0; i<n; i++)
{
for (j = 0; j<calc; j++)
{
if(a[i] == b[j])
break;
}
if (j== calc)
{
b[count] = a[i];
calc++;
}
}
printf(“Array obtained after removing duplicate elements”);
for (i = 0; i<calc; i++)
{
printf(“%dn”, b[i]);
}
return 0;
}
14. Write a program for checking whether the given number is palindrome or not without a recursive method
#include <stdio.h>
#include <conio.h>
int reverse(int num);
int isPalindrome(int num);
int main()
{
int num;
printf(“Enter a number: “);
scanf(“%d”, &num);
if(isPalindrome(num) == 1)
{
printf(“the given number is a palindrome”);
}
else
{
printf(“the given number is not a palindrome number”);
}
return 0;
}
int isPalindrome(int num)
{
if(num == reverse(num))
{
return 1;
}
return 0;
}
int reverse(int num)
{
int rem;
static int sum=0;
if(num!=0){
rem=num%10;
sum=sum*10+rem;
reverse(num/10);
}
else
return sum;
return sum;
}
Output
Enter a number: 1331
The given number is a palindrome
15. Write a program to find n’th Fibonacci Number
The fact that every number after the first two is the sum of the two numbers before it divides the Fibonacci number sequence.
Example, 0, 1, 1, 2, 3, 3, 8, 13, 21, 34, 55, 89, .. etc. Now, we have to find F{n} = F{n-1} + F{n-2} with base values F(0) = 0 and <code> F(1) = 1.
// Function to find the nth Fibonacci number
int fib(int n)
{
if (n <= 1) {
return n;
}
return fib(n – 1) + fib(n – 2);
}
int main()
{
int n = 8;
printf(“nth Fibonacci number is %d”, fib(8));
return 0;
}
16. Explain class and objects in C++
A class is a user-defined data type that has data members and functions. Data variables are known as data members and functions are used to perform operations on the variables.
An object is an instance created for a class, as the class is a user-defined data type for an object to be called a variable of the data type.
Example
class A
{
private:
int data;
public:
void fun()
{
}
};
17. Differentiate struct and class in C++
The structure has members or variables that can be public by default but the members of the class are private by default. The default access specifier for a base class or struct is public when deriving a struct from a class but the default access specifiers will be private when deriving a class.
18. Explain polymorphism with its types and examples
Polymorphism is a thing that has many forms with various behaviors for different situations. It occurs when we use multiple classes for inheritance purposes. There are two types of polymorphism and they are compile-time polymorphism and runtime polymorphism.
Compile-time polymorphism: In this, we will know which method to call when the compile-time and the call are resolved by the compiler. It offers fast execution; which is known as compile time. It will be achieved by function overloading and operator overloading.
Example
int add(int a, int b){
return a+b;
}
int add(int a, int b, int c){
return a+b+c;
}
int main(){
cout<<add(2,3)<<endl;
cout<<add(2,3,4)<<endl;
return 0;
}
Runtime Polymorphism: In this method, we will know which method to call during the runtime and the call will not be resolved by the compiler. It offers slow execution as it is known at runtime only. It will be achieved by virtual functions and pointers.
Example
class A
{
public:
virtual void fun()
{
cout<<“base “;
}
};
class B: public A
{
public:
void fun()
{
cout<<“derived “;
}
};
int main()
{
A *a=new B;
a->fun();
return 0;
}
19. What are the access specifiers in C++?
C++ programming language has the following access specifiers
Public: All the data members and member functions can be accessed outside the class
Protected: All the data members and member functions are accessible inside the class and the derived class.
Private: No data members or member functions can be called outside the class
20. How to call a virtual function from a constructor
We can call a virtual function from a constructor but the behavior is a little varied. Once the virtual function is called, it resolves a virtual call at runtime. It is the number function of the present class that gets called and the virtual machine will not work within the constructor.
Example
class base
{
private:
int value;
public:
base(int x){
value=x;
}
virtual void fun()
{
}
}
class derived
{
private:
int a;
public:
derived(int x, int y):base(x){
base *b;
b=this;
b->fun(); //calls derived::fun()
}
void fun(){
cout<<”fun inside derived class”<<endl;
}
}
Conclusion
C and C++ are the in-demand skills for every IT aspirant to understand the fundamentals of programming. We provide updated C and C++ interview questions and answers to help clear the technical rounds easily. Learn the best C and C++ training in Chennai.
