Top 40 C Programming Interview Questions

What are the features of the c programming language?
Programming Interview Questions
Q01
• Simple and Portable
• Middle-Level Language
• Feature of Modularity
• Rich in Library
• Procedural Language
• Easy to Extend
• Built-in operations
• Memory Management

Mention different data types in c.
Q02
Datatypes
Basic datatypes
Derived datatypes
User-defined datatypes
int
char
float
double
array
Structures
pointers
unions
enum

What is the use of static function?
Q03
Functions declared with the keyword static are
static functions. They have the scope restricted
only to the function in which they are declared.

Mention the dynamic memory allocation functions
Q04
• malloc()
• Calloc()
• realloc()
• free()

What is the difference between the local variable and the global variable?
Q05
Variables declared inside the functions with the
keyword local are called local variables. The
local variable's scope is inside the function in
which it is declared.
Variables declared outside the functions with the
keyword global are called global variables. And
they can be accessed by multiple functions
defined in the program.

What is the use of pointer variables in c programming and what do u mean
by dangling pointer variable?
Q06
a
200
10
200
204
Variables declared outside the functions with the
keyword global are called global variables. And they
can be accessed by multiple functions defined in the
program.

What is nested structure?
Q07
Nested structures are a structure
where the data member of one
structure is referred to by the data
member of another function.

What is the use of break control statements?
Q08
The break is used to terminate the
loop. So, Whenever the control
encounters the break statement it will
stop the loop iteration and transfer the
control to the next statement soon
after the loop.

What are c tokens?
Q09
• Keywords
• Identifiers
• Constants
• Special Symbols
• Strings
• Operators.

what is a predefined function in c?
Q10
Pre-defined functions are built-in
functions. It helps the user to use
the already existing code in the
program.

What is the use of prinf() and scanf() functions?
Q11
printf() and scanf() are inbuilt library
functions defined in the standard input
output header file
Scanf () is used to read the input
from the user and printf() is used to
print the output on the console.

What is the use of header files in c?
Q12
Header files contain the pre-defined
library functions. Programmers can
make use of standard library
functions By defining #include in
the program.
It reduces the number of codes and
complexity of the program.

What is an array? mentions its different types.
Q13
An array is a homogenous collection of
elements of the same data type; That means
similar types of elements are stored under one
name called an array name. And the array of
elements is stored in a consecutive block of
memory.
Types of arrays are:
• One-dimensional array
• Two- dimensional array
• Multi-dimensional array

What is the use of the const keyword?
Q14
Using a const keyword, the value of a
variable is constant throughout the
program run-time. Constant values
are unchangeable.
Syntax: Const <data type>
variable-name = value;

What is a memory leak?
Q15
When the memory is allocated
dynamically and not deallocated even
when the memory is no longer required,
that leads to a memory leak.

Differentiate between call by value and call by reference.
Q01
Call by value Call by reference
In call by value; we pass values by
copying variables
In call by reference; we pass the
address of the variable.
In call by value, the memory location
for formal and actual arguments is
created separate
In case of call by reference; the
formal and actual arguments share
the same memory location
Any changes made in a copy of
variable will not affect the value of a
variable outside the function in call by
value.
Whereas, in call by reference Any
changes made in the variable will also
affects the value of a variable outside
the function.

What is the difference between a compiler and an interpreter?
Q02
• A compiler compiles the whole code
at a time. And displays all the
errors.
• The interpreter executes the
program line by line and displays
the error of every single line.

What are the entry and exit loops in c?
Q03
A loop in which the condition is checked first
and then executes the statements is known as
an entry loop.
For example, a while loop is an entry loop
A loop in which the set of statements is
executed first and then checks the given
condition is known as an exit loop. For
example, the do-while loop is an exit loop.

What is typecasting?
Q04
Typecasting is a process of converting one
data type to another data type.
The conversion that is done automatically
is known as an implicit conversion.

Mention four types of storage classes in c.
Q05
•Automatic
•Register
•Static
•And External

What is the use of size of an operator in c?
Q06
The sizeof operator is applied to data types such
as int, char, float, etc. to determine the exact
size of a variable, in bytes.

What are string handling functions in c?
Q07
String handling functions are:
•strlen()- to find a string's length. It will count the
number of characters in a string and prints the
output.
•strcat()-Then strcat() is used to concatenate
two strings. which means adding up two
strings.
•strcpy()- is to copy a string to another.
•strcmp()- is to compare two strings.

Write a c program to print the following pattern
Q08
1
1 2
1 2 3
1 2 3 4
1 2 3 4 5

Write a c code to print the Pyramid star pattern program
Q09

Write a c code to swap two numbers without using a third variable
Q10

What is a union?
Q01
Union is a special data type that holds elements of
different data types at the same memory location.

What are enumeration?
Q02
Enum is a user-defined data type consisting
of an integral constant

What is a recursion?
Q03
Recursion is a process of making a function
call itself.
In short, the user call function inside the
same function.

What are macros in c?
Q04
Macro in c is defined by the #define directive.
Macro is a name given to a piece of code, so
whenever the compiler encounters a macro in a
program, it will replace it with the macro value.
Syntax of a macro:
define macro_name macro_value;
Example:
#define pi 3.14;

What are file operations in c?
Q05
• Creating a file
• Writing a file
• Reading a file
• Seek operation
• Truncating a file
• Deleting a file

Write the difference between macros and functions.
Q06
Macros Functions
Macros are preprocessed But, Functions are compiled
Using macros execution speed is
faster
In case of functions the Speed of
execution is slower.
Macro name is replaced by
macro value, before compilation
Whereas in functions, Transfer of
control takes place during the
function call
Using macros, the length of the
code increase
The code length is unaffected
using function

Sort an array using a quick sort algorithm
Q07

Implement a program to print the factorial of a given number using recursive
method.
Q08

Write a c code to find the Fibonacci series.
Q09

Write a program to check whether a given number is a prime number.
Q10

How to Implement a program to find the height of a binary tree?
Q11

Write a C code to find the n terms of odd natural numbers and find their sum.
Q12

Implement a C program to display a string in reverse order.
Q13

Implement a program to remove duplicates in a sorted array.
Q14

Implement a program to add a node at the beginning, end, and specified
positions in any linked list.
Q15

Top 40 C Programming Interview Questions

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