C Program to print the first N prime numbers

#include "stdio.h"
void prime (int);
void main ()
{
  int num;
  clrscr ();
  printf ("Enter the number\n");
  scanf ("%d", &num);
  prime (num);
  getch ();
}
void prime (n)
{
  int a;
  printf ("List of prime number upto %d:-",n);
  for (a = 1; a < = n; a++)
  {
    if( (a==2) || (a==3) || (a==5) )
    {
      printf ("\n%d", a);
    }
    if ( (a%2 ! = 0) && (a%3 ! = 0) && (a%5 ! = 0) )
    {
      printf ("\n%d", a);
    }

  }
}