在Windows系统上，用C语言编写闹钟程序。

一、用do...while语句实现循环响铃

 1 /*此程序用do...while语句实现循环响铃*/
 2 
 3 #include <stdio.h>
 4 
 5 #include <windows.h>
 6 
 7 #include <winbase.h>
 8 
 9 int main()
10 
11 { char f='Y';
12 
13 SYSTEMTIME time;
14 
15 SYSTEMTIME clock;
16 
17 GetLocalTime(&time);
18 
19 printf("当前时间为：%2d:%2d:%2d\n",time.wHour,time.wMinute,time.wSecond);
20 
21 printf("请设定闹钟时间：\n");
22 
23 printf("时：");
24 
25 scanf("%2d",&clock.wHour);
26 
27 printf("分：");
28 
29 scanf("%2d",&clock.wMinute);
30 
31 getchar();//读取掉回车符 
32 
33 Sleep(1000);
34 
35 GetLocalTime(&time);
36 
37 if((time.wHour==clock.wHour)&&(time.wMinute==clock.wMinute))
38 
39 {
40 
41 printf("\a\a\a时间到!!!");
42 
43 }
44 
45 do
46 
47 {printf("是否继续响铃？输入y继续，其他任意键取消:");
48 
49 scanf("%c",&f);
50 
51 getchar();//读取掉回车符 
52 
53 Sleep(2000);
54 
55 if(f=='y')
56 
57  {printf("\a\a\a时间到!!!");
58 
59  }
60 
61 }while(f=='y');
62 
63 return 0;
64 
65 }

二、用for循环实现循环响铃

 1 #include <stdio.h>
 2 
 3 #include <windows.h>
 4 
 5 int main()
 6 
 7 {
 8 
 9     SYSTEMTIME time;
10 
11     SYSTEMTIME clock;
12 
13     GetLocalTime(&time);
14 
15     char flag;
16 
17     int i;
18 
19     printf("当前时间为：%2d:%2d:%2d\n",time.wHour,time.wMinute,time.wSecond);
20 
21     printf("请设定闹钟时间：\n");
22 
23     printf("时：");
24 
25     scanf("%d",&clock.wHour);
26 
27     printf("分：");
28 
29     scanf("%d",&clock.wMinute);
30 
31     getchar();
32 
33     Sleep(1000);
34 
35     GetLocalTime(&time);
36 
37     if((time.wHour==clock.wHour)&&(time.wMinute==clock.wMinute))
38 
39     {
40 
41         for(i=1;i<10000;i++)
42 
43         { 
44 
45             printf("\a\a\a时间到!!!\n");
46 
47               Sleep(3000);
48 
49               printf("按n键取消，其他任意键继续响铃！");
50 
51               scanf("%c",&flag);
52 
53               getchar();
54 
55               Sleep(5000);
56 
57               if (flag=='n')
58 
59               {
60 
61               i=9999;
62 
63             }
64 
65           }
66 
67     }
68 
69 }