1 #include <stdio.h>
2 #include <math.h>
3 #include <stdlib.h>
4 void writefile()
5 {
6 FILE *fp;
7 fp = fopen("e://ss.txt","w+");
8 if(fp == NULL)
9 {
10 exit(0);
11 }
12 int i=2, a=100, flag=0,count = 0;
13 for (a=2;a<=1000;a++)
14 {
15 flag=0;
16 i= 2;
17 while (i<=sqrt(a))
18 {
19 if (a%i==0)
20 {
21 flag=1;
22 break;
23 }
24 i++;
25 }
26 if (flag==0)
27 {
28 count++;
29 // printf("%5d",a);
30 fprintf(fp,"%5d",a);
31 if(count % 10 == 0)
32 {
33 // printf("\n");
34 fprintf(fp,"\n");
35 }
36 }
37 }
38 fclose(fp);
39 }
40 void readfile()
41 {
42 char str[1024];
43 FILE *fp;
44 fp = fopen("e://ss.txt","r");
45 if(fp == NULL)
46 {
47 exit(0);
48 }
49 while(!feof(fp))
50 {
51 fgets(str,1024,fp);
52 printf("%s", str);
53 }
54 printf("\n");
55 fclose(fp);
56 }
57 int main()
58 {
59 writefile();
60 readfile();
61 return 0;
62 }
