**Ex:**Write a C program to print alternate prime numbers from 1 to n. How to write a C program to print alternate prime numbers from 1 to n. C program to print alternate prime numbers from 1 to n.

**Input from user:**

Enter the number: 100

**Expected output:**

2 5 11 17 23 31 41 47 59 67 73 83 97

**What is prime number?**

Prime number means a number that is divisible only by 1 and itself.

** **** Step by step logic of the given program:**

1. Accept input from user declare variable say no.

**2.**Declare e=2.

3. Run one outer

**for loop**from 1 to no:for(i=1;i<=no;i++)

4. Run one inner

**for loop**from 1 to i and inside that check condition if**i%j == 0**then increment c by 1:for(j=1;j<=i;j++)

{

if(i%j==0)

{

c++;

}

}

5. After that outside the inner

**for loop**check if**c==2**(it means if given number is prime) then, inside that**if-statement**check one more condition if**e%2==0**means if e is even number then print value of**i**(it prints prime numbers only if e is completely divisible by 2, in short it prints alternate prime numbers):if(c==2)

{

if(e%2==0)

{

printf("%d ",i);

}

6. After that, Outside the block of inner if statement increment value of e by 1.

7. Last make c=0.

** Program to Print Alternate Prime Numbers:**

#include<stdio.h>

void main()

{

int no,i,j,c=0,e;

printf("Enter the number:\n");

scanf("%d",&no);

e=2;

printf("Alternate Prime Number's Are:\n");

for(i=1;i<=no;i++)

{

for(j=1;j<=i;j++)

{

if(i%j==0)

{

c++;

}

}

if(c==2)

{

if(e%2==0)

{

printf("%d ",i);

}

e=e+1;

}

c=0;

}

}

Above Program show's the following output:

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