C Programming Interview Questions and Answers for Freshers

Author Full Stack Tutorials
Last Updated - October 20, 2018

C Programming Interview Questions: C is a general-purpose, structured & imperative computer programming language. It is developed by - Dennis Ritchie.

C Programming Interview Questions

1.) Write A Program in C to check whether Number is even or odd?

#include
int main(){
    int number; 
    printf("Enter any integer: ");
    scanf("%d",&number);
    if(number % 2 ==0)
         printf("%d is even number.",number);
    else
         printf("%d is odd number.",number);
  
    return 0;
}

Output:
Enter any integer: 5
5 is an odd number.

2.) Write a Program to swap two number without using 3rd variable?

There are two common ways to swap two numbers without using third variable:

By using + and -
By using * and /

Method 1: Using + and -

Let's see a simple c example to swap two numbers without using the third variable.

#include 
#include 
main() 
{ 
int a=10, b=20; 
clrscr(); 
printf("Before swap a=%d b=%d",a,b); 
 
a=a+b;//a=30 (10+20) 
b=a-b;//b=10 (30-20) 
a=a-b;//a=20 (30-10) 
 
printf("\nAfter swap a=%d b=%d",a,b); 
getch(); 
} 
Output:
Before swap a=10 b=20
After swap a=20 b=10

Method 2: Using * and /

Let's see another example to swap two numbers using * and /.

#include 
#include 
main() 
{ 
int a=10, b=20; 
clrscr(); 
printf("Before swap a=%d b=%d",a,b); 
 
a=a*b;//a=200 (10*20) 
b=a/b;//b=10 (200/20) 
a=a/b;//a=20 (200/10) 
 
printf("\nAfter swap a=%d b=%d",a,b); 
getch(); 
} 
Output:
Before swap a=10 b=20
After swap a=20 b=10

3) Write a program to print "Full Stack Tutorials" without using semicolon?

Method: 1
void main(){
if(printf("Full Stack Tutorials")){
}
}

Method: 2
void main(){
while(!printf("Full Stack Tutorials")){
}
}

Method: 3
void main(){
switch(printf("Full Stack Tutorials")){
}
}

4.) Write a C program to display fibonacci series without using recursion?

Fibonacci Series: In case of fibonacci series, next number is the sum of previous two numbers.

for example 0, 1, 1, 2, 3, 5, 8, 13, 21 etc. The first two numbers of fibonacci series are 0 and 1.

There are two ways to write the fibonacci series program:

Fibonacci Series without recursion
Fibonacci Series using recursion

Write a C program to display fibonacci series using recursion?

Fibonacci Series using recursion in C

Let's see the fibonacci series program in c using recursion.

#include 
#include 
void printFibonacci(int n){ 
 static int n1=0,n2=1,n3; 
 if(n>0){ 
 n3 = n1 + n2; 
 n1 = n2; 
 n2 = n3; 
 printf("%d ",n3); 
 printFibonacci(n-1); 
 } 
} 
void main(){ 
 int n; 
 clrscr(); 
 printf("Enter the number of elements: "); 
 scanf("%d",&n); 
 
 printf("Fibonacci Series: "); 
 printf("%d %d ",0,1); 
 printFibonacci(n-2);//n-2 because 2 numbers are already printed 
 
 getch(); 
} 
Output:

Enter the number of elements:15
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377

5.) Write a C program to check whether a number is prime or not ?

#include 
#include 
void main() 
{ 
int n,i,m=0,flag=0; 
clrscr(); 
printf("Enter the number to check prime:"); 
scanf("%d",&n); 
m=n/2; 
for(i=2;i<=m;i++) 
{ 
if(n%i==0) 
{ 
printf("Number is not prime"); 
flag=1; 
break; 
} 
} 
if(flag==0) 
printf("Number is prime"); 
getch(); 
} 
Output:

Enter the number to check prime:56
Number is not prime
Enter the number to check prime:23
Number is prime

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6.) Write a C program to check whether a number is a palindrome or not?

A palindrome number is a number such that if we reverse it, it will not change.

The first 15 palindromic numbers (in decimal) are: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55,...

#include 
#include 
main() 
{ 
int n,r,sum=0,temp; 
clrscr(); 
printf("enter the number="); 
scanf("%d",&n); 
temp=n; 
while(n>0) 
{ 
r=n%10; 
sum=(sum*10)+r; 
n=n/10; 
} 
if(temp==sum) 
printf("palindrome number "); 
else 
printf("not palindrome"); 
getch(); 
} 
Output:

enter the number=151
palindrome number
enter the number=5621
not palindrome number

7.) Write a C program to print factorial of given number without using recursion?

Methods:
Factorial Program using loop
Factorial Program using recursion


Factorial Program using the loop

Let's see the factorial Program using the loop.

#include 
#include 
void main(){ 
 int i,fact=1,number; 
 clrscr(); 
 printf("Enter a number: "); 
 scanf("%d",&number); 
 
 for(i=1;i<=number;i++){ 
 fact=fact*i; 
 } 
 printf("Factorial of %d is: %d",number,fact); 
 getch(); 
} 
Output:

Enter a number: 5
Factorial of 5 is: 120
Factorial Program using recursion in C

Let's see the factorial program in c using recursion.

#include 
#include 
 
long factorial(int n) 
{ 
 if (n == 0) 
 return 1; 
 else 
 return(n * factorial(n-1)); 
} 
 
void main() 
{ 
 int number; 
 long fact; 
 clrscr(); 
 printf("Enter a number: "); 
 scanf("%d", &number); 
 
 fact = factorial(number); 
 printf("Factorial of %d is %ld\n", number, fact); 
 getch(); 
} 
Output:

Enter a number: 6
Factorial of 5 is: 720

8.)Write a C Program to reverse the given number?

#include 
#include 
main() 
{ 
int n, reverse=0, rem; 
clrscr(); 
printf("Enter a number: "); 
 scanf("%d", &n); 
 while(n!=0) 
 { 
 rem=n%10; 
 reverse=reverse*10+rem; 
 n/=10; 
 } 
 printf("Reversed Number: %d",reverse); 
getch(); 
} 
Output:

Enter a number: 123
Reversed Number: 321

9.)Write a C program which produces its own source code as its output?


#include

int main(){
    FILE *fp;
    char c;

    fp = fopen(__FILE__,"r");
 
    do{
         c= getc(fp);
         putchar(c);
    }
    while(c!=EOF);

    fclose(fp);
   
    return 0;
}

Output:
#include

int main(){
    FILE *fp;
    char c;

    fp = fopen(__FILE__,"r");
 
    do{
         c= getc(fp);
         putchar(c);
    }
    while(c!=EOF);

    fclose(fp);
   
    return 0;
}