find number.c

计算十亿以内的素数 并以文本形式存储. 通过更改参数可以缩小范围

#include "math.h"
#include "stdio.h"
#include "string.h"
/*此函数实现计算一定范围内的素数 以文本形式存储*/
main()
{ 
	long m,j,k,prime;
	FILE *infp,*outfp;
    //char inname[40]={"00.txt"},outname[40]={"primenumber.txt"};
    char inname[40]={"00.txt"},outname[10][10]={"01.txt","02.txt","03.txt",
		 "04.txt","05.txt","06.txt","07.txt","08.txt","09.txt","10.txt"};
    int i=0;
    if((outfp=fopen(outname,"w"))==NULL)
    {printf("Can't open the 01.out.\n");
    exit(0);
    }
  /*c语言能表示的最大正整数2147483647 上一次计算到1512331*/
    for(m=2;m<=1000000000;m++)
    {
	  
	  if((infp=fopen(inname,"r"))==NULL)
	  {
		  printf("Can't open the %s\n",inname);
          exit(0);
	  }
	  
	  k=sqrt(m)+1;
      prime=1;
      for(j=2;j<k;fscanf(infp,"%d",&j))//
      if(m%j==0)
      {
       prime=0;
       break;
      }

	  fclose(infp);

      if(prime)
      {
		  printf("%16d",m);
     	  fprintf(outfp,"%10d ",m);    
	  }

	  if(m%1000000==0)
	  {
		  fclose(outfp);
		  i++;
		  if((outfp=fopen(outname[i],"w"))==NULL)
		  {
		  printf("Can't open the 01.out.\n");
          exit(0);
		  }
	  }

    }  
   fclose(outfp);
   
    //printf("The primes between 100&200 are:\n");
   

	
    printf("\n");
}