C Interview Questions — 2022

C is a general purpose high-level language most popular amongst coders, it is the most compatible, easy to learn and effective programming language. It is a successor of the B language that came out way back in the 70s and has been the most popular programming language ever since.

Following are some important C Interview Questions

1. When should we use pointers in a C program?

a. To get address of a variable

b. For achieving pass by reference in C: Pointers allow different functions to share and modify their local variables.

c. To pass large structures so that complete copy of the structure can be avoided.

d. To implement “linked” data structures like linked lists and binary trees.

2.Write a program to print "hello world" without using a semicolon?

Ans: 

3.What is NULL pointer?

Ans: NULL is used to indicate that the pointer doesn’t point to a valid location. Ideally, we should initialize pointers as NULL if we don’t know their value at the time of declaration. Also, we should make a pointer NULL when memory pointed by it is deallocated in the middle of a program.

4.What is Dangling pointer?

Ans: Dangling Pointer is a pointer that doesn’t point to a valid memory location. Dangling pointers arise when an object is deleted or deallocated, without modifying the value of the pointer, so that the pointer still points to the memory location of the deallocated memory. Following are examples.

5.What is memory leak? Why it should be avoided

Ans: Memory leak occurs when programmers create a memory in heap and forget to delete it. Memory leaks are particularly serious issues for programs like daemons and servers which by definition never terminate.

6.What is difference between i++ and ++i? 

a) The expression ‘i++’ returns the old value and then increments i. The expression ++i increments the value and returns new value. 

b) Precedence of postfix ++ is higher than that of prefix ++. 

c) Associativity of postfix ++ is left to right and associativity of prefix ++ is right to left. 

d) In C++, ++i can be used as l-value, but i++ cannot be. In C, they both cannot be used as l-value. 

7.What is the difference between Call by Value and Call by Reference?

When using Call by Value, you are sending the value of a variable as parameter to a function, whereas Call by Reference sends the address of the variable. Also, under Call by Value, the value in the parameter is not affected by whatever operation that takes place, while in the case of Call by Reference, values can be affected by the process within the function.

8.What is typecasting?

The typecasting is a process of converting one data type into another data type. Suppose If we want to store the floating type value to an int type, then we will use typecasting to convert floating point data type into int data type explicitly.

Ex: int i = (int) 3.4

9.Difference between malloc() and calloc() functions?

10.What is dynamic memory allocation?

In dynamic memory allocation, memory is allocated at runtime. We can increase memory while executing the program. The malloc() or calloc() function is used to allocate the memory at the runtime. Dynamic memory allocation is used in linked list.

11.What is static memory allocation?

In static memory allocation, memory is allocated during compile time. And we cannot increase memory while executing the program. Array use the static memory allocation. lifetime of a variable in static memory is the lifetime of the program. It applies to global variables, file scope variables etc.The static memory is implemented using stacks or heap.

For example: int arr[20]; The above example creates an array of integer type, and the size of an array is fixed, i.e., 20.

12.Differentiate between getch() and getche().

Ans. The only difference between the two roles is that one reads characters from the keyboard and the other does not. getch() is a function that reads characters from the keyboard without using any buffers. As a result, no data is shown on the computer. getche() uses a buffer to read characters from the keyboard. As a result, information is shown on the projector.