how to print first n primes?

[janutovianca]

hey there!!!

we were asked to make a code for printing prime numbers from 3 until the [I]n[I]th prime number but i can't seem to find the right solution for this one.

when i print my work it prints some other numbers that has the factor of another prime number

it prints the numbers:
3, 5, 7, 9 ,11, 13, 15...

i'm a beginner here, so please help me.
i really would appreciate your helping me.
thanks.

[Dheeraj Joshi]

Does it print

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59

this?

These are prime numbers.
Can we have a look at your code?

Regards
Dheeraj Joshi

[Banfa]

Well from the look of your output you are just printing all the odd numbers rather than checking if a number is prime before printing it.

[donbock]

The basic logic of your program is

   number_of_primes = 0;
   candidate = 1;
   Repeat until number_of_primes == threshold {
      if candidate is a prime {
         print the candidate
         increment number of primes
      }
   }

The challenge is determining if the candidate is a prime. Forget about computer programs for a moment. Let's talk mathematics first: how can you tell if a number is prime? There is no point writing code until you have a firm grasp on this.

[janutovianca]

actually...i've already got how to print prime numbers but the next problem i'm having now is how to print the first n primes, not the prime numbers from 0 to n.

i really did appreaciate your replies.

this is my code:

#include<stdio.h> 

main() 
{ 
int x,y,n; 
printf(" Enter n: "); 
scanf("%d",&n); 
printf("\n"); 


for(x=3;x<=n;x++) 
{
for(y=2;y<=x-1;y++) 
if(x%y==0) 
break; 
if(x==y) 
printf("\t%d\n",x);
}


}

i really would like your help...thanks

[Banfa]

In your for loop instead of the end condition being a test against x, the current number you are checking, you need to use a separate variable to keep a count of the number of primes you have found and test against that instead.

Also your loop at line 13 works but has a lot of scope for optimisation.

[donbock]

Both loops involve comparisons against x. The one Banfa wants you to change is the outermost loop at line 11.

By the way, "2' is a prime number too.