C PROGRAM TO PRINT PRIME NUMBERS UPTO N

 

Hi Friends

Now we are going to learn about print prime numbers upto n.

Sample input

20

Sample out put.

2  3  5  7

Program

#include<stdio.h> int main() { int n,i,j,count; scanf("%d",&n); for(i=0; i<=n; i++) { count=0; for(j=0; j<i; j++) { if(i%j==0) { count++; } } if(count==2) { printf("%d ",i); } } }

Click Here To RUN The Program

You can also copy the program below

#include<stdio.h>

int main()
{
int n,i,j,count;
scanf("%d",&n);
for(i=0; i<=n; i++)
{
   count=0;
    for(j=0; j<i; j++)
     {
         if(i%j==0)
         {
          count++;
         }
   }
       if(count==2)
       {
       printf("%d ",i);
         }
   }
}

CLICK HERE TO RUN THE PROGRAM

Explination -

In this program we have to check the condition of prime number . 

We know that a number is said to be a prime number when it has only two factors that are 1 and itself( ex- 5 has factors 1 and 5). 

 so we use nested loops to check all numbers from 2 to n .       

In first loop we take numbers from 2 (becuase 1st prime number is 2) and increment the value upto n. 

And in second loop we take numbers from 1 to i. Here we check the factors of i. If i%j==0 we increase the count value(initially we take count=0) . And if count ==2 means the number have two factors.

So we print (i) that is the prime number.