VC 回调函数是什么
VC 回调函数是如何工作的啊，都说回调函数就是传送函数地址，那他是怎么实现回调呢，回调怎么解释呢？
不要拷贝网上资料，我都能找到。 VC 回调函数
[解决办法]
通常来说, 软件系统是按层次划分的.
上层可以调用下层的函数, 下层不能直接调用上层的函数.
比如我们可以调用操作系统的 API, 但是操作系统没办法调用我们的函数, 因为操作系统先实现的, 代码也不能随时改. 但是, 有些时候确实需要反过来调用, 比如窗口产生消息的时候, 操作系统希望调用一个我们写的函数来处理这个窗口消息, 这是就需要使用回调了, 系统定义好了回调的函数的原型, 我们使用某种方法把实现的这个函数的地址告诉系统, 然后系统就会在发生消息的时候调用我们的函数了.
[解决办法]
类似这样的机制：

typedef void (*call_back_t)(void);
...
static call_back_t this_cb = NULL;
/* 注册回调函数 */
void timer_init(call_back_t cb)
{
    this_cb = cb;
}
...
/* 定时服务 */
void timer_isr(void)
{
    if(this_cb != NULL)
        this_cb();
}
...

[解决办法]
Windows系统：“不要调用我，请先填写好未来收到某个消息时你的处理流程，在那个消息到来时我会调用你！”

[解决办法]

#pragma comment(lib,"user32")
#include <stdio.h>
#include <time.h>
#include <sys/timeb.h>
#include <windows.h>
char datestr[16];
char timestr[16];
char mss[4];
void log(char *s) {
    struct tm *now;
    struct timeb tb;

    ftime(&tb);
    now=localtime(&tb.time);
    sprintf(datestr,"%04d-%02d-%02d",now->tm_year+1900,now->tm_mon+1,now->tm_mday);
    sprintf(timestr,"%02d:%02d:%02d",now->tm_hour     ,now->tm_min  ,now->tm_sec );
    sprintf(mss,"%03d",tb.millitm);
    printf("%s %s.%s %s",datestr,timestr,mss,s);
}
VOID CALLBACK myTimerProc1(
  HWND hwnd, // handle of window for timer messages
  UINT uMsg, // WM_TIMER message
  UINT idEvent, // timer identifier
  DWORD dwTime // current system time
) {
 log("In myTimerProc1\n");
}
VOID CALLBACK myTimerProc2(
  HWND hwnd, // handle of window for timer messages
  UINT uMsg, // WM_TIMER message
  UINT idEvent, // timer identifier
  DWORD dwTime // current system time
) {
 log("In myTimerProc2\n");
}
int main() {
    int i;
    MSG msg;

    SetTimer(NULL,0,1000,myTimerProc1);
    SetTimer(NULL,0,2000,myTimerProc2);
    for (i=0;i<20;i++) {
        Sleep(500);
        log("In main\n");
        if (GetMessage(&msg,NULL,0,0)) {
            TranslateMessage(&msg);
            DispatchMessage(&msg); 
 
        }

    }
    return 0;
}
//2012-07-26 17:29:06.375 In main
//2012-07-26 17:29:06.875 In myTimerProc1
//2012-07-26 17:29:07.375 In main
//2012-07-26 17:29:07.875 In myTimerProc2
//2012-07-26 17:29:08.375 In main
//2012-07-26 17:29:08.375 In myTimerProc1
//2012-07-26 17:29:08.875 In main
//2012-07-26 17:29:08.875 In myTimerProc1
//2012-07-26 17:29:09.375 In main
//2012-07-26 17:29:09.890 In myTimerProc2
//2012-07-26 17:29:10.390 In main
//2012-07-26 17:29:10.390 In myTimerProc1
//2012-07-26 17:29:10.890 In main
//2012-07-26 17:29:10.890 In myTimerProc1
//2012-07-26 17:29:11.390 In main
//2012-07-26 17:29:11.890 In myTimerProc2
//2012-07-26 17:29:12.390 In main
//2012-07-26 17:29:12.390 In myTimerProc1
//2012-07-26 17:29:12.890 In main
//2012-07-26 17:29:12.890 In myTimerProc1
//2012-07-26 17:29:13.390 In main
//2012-07-26 17:29:13.890 In myTimerProc2
//2012-07-26 17:29:14.390 In main
//2012-07-26 17:29:14.390 In myTimerProc1
//2012-07-26 17:29:14.890 In main
//2012-07-26 17:29:14.890 In myTimerProc1
//2012-07-26 17:29:15.390 In main
//2012-07-26 17:29:15.890 In myTimerProc2
//2012-07-26 17:29:16.390 In main
//2012-07-26 17:29:16.390 In myTimerProc1
//2012-07-26 17:29:16.890 In main
//2012-07-26 17:29:16.890 In myTimerProc1
//2012-07-26 17:29:17.390 In main
//2012-07-26 17:29:17.890 In myTimerProc2
//2012-07-26 17:29:18.390 In main
//2012-07-26 17:29:18.390 In myTimerProc1
//2012-07-26 17:29:18.890 In main
//2012-07-26 17:29:18.890 In myTimerProc1
//2012-07-26 17:29:19.390 In main
//2012-07-26 17:29:19.890 In myTimerProc2