diff --git a/12_day/bootpack.h b/12_day/bootpack.h
index d42a313..fdd47ed 100644
--- a/12_day/bootpack.h
+++ b/12_day/bootpack.h
@@ -176,8 +176,9 @@ struct TIMER {
 	unsigned char data;
 };
 struct TIMERCTL {
-	unsigned int count, next;
-	struct TIMER timer[MAX_TIMER];
+	unsigned int count, next, using;
+	struct TIMER *timers[MAX_TIMER];
+	struct TIMER timers0[MAX_TIMER];
 };
 extern struct TIMERCTL timerctl;
 
diff --git a/12_day/timer.c b/12_day/timer.c
index e936ffb..cc773ef 100644
--- a/12_day/timer.c
+++ b/12_day/timer.c
@@ -17,8 +17,9 @@ void init_pit(void)
 	io_out8(PIT_CNT0, 0x2e);
 	timerctl.count = 0;
 	timerctl.next = 0xffffffff; /* 因为最初没有正在运行的定时器 */
+	timerctl.using = 0;
 	for (i = 0; i < MAX_TIMER; i++) {
-		timerctl.timer[i].flags = 0; /* 未使用 */
+	timerctl.timers0[i].flags = 0; /* 未使用 */
 	}
 	return;
 }
@@ -27,9 +28,9 @@ struct TIMER *timer_alloc(void)
 {
 	int i;
 	for (i = 0; i < MAX_TIMER; i++) {
-		if (timerctl.timer[i].flags == 0) {
-			timerctl.timer[i].flags = TIMER_FLAGS_ALLOC;
-			return &timerctl.timer[i];
+		if (timerctl.timers0[i].flags == 0) {
+			timerctl.timers0[i].flags = TIMER_FLAGS_ALLOC;
+			return &timerctl.timers0[i];
 		}
 	}
 	return 0; /* 没找到 */
@@ -50,37 +51,56 @@ void timer_init(struct TIMER *timer, struct FIFO8 *fifo, unsigned char data)
 
 void timer_settime(struct TIMER *timer, unsigned int timeout)
 {
+	int e, i, j;
 	timer->timeout = timeout + timerctl.count;
 	timer->flags = TIMER_FLAGS_USING;
-	if (timerctl.next > timer->timeout) {
-		/* 更新下一次的时刻 */
-		timerctl.next = timer->timeout;
+	e = io_load_eflags();
+	io_cli();
+	/* 搜索注册位置 */
+	for (i = 0; i < timerctl.using; i++) {
+		if (timerctl.timers[i]->timeout >= timer->timeout) {
+			break;
+		}
 	}
+	/* i号之后全部后移一位 */
+	for (j = timerctl.using; j > i; j--) {
+		timerctl.timers[j] = timerctl.timers[j - 1];
+	}
+	timerctl.using++;
+	/* 插入到空位上 */
+	timerctl.timers[i] = timer;
+	timerctl.next = timerctl.timers[0]->timeout;
+	io_store_eflags(e);
 	return;
 }
 
 void inthandler20(int *esp)
 {
-	int i;
+	int i, j;
 	io_out8(PIC0_OCW2, 0x60); /* 把IRQ-00信号接收完了的信息通知给PIC */
 	timerctl.count++;
 	if (timerctl.next > timerctl.count) {
 		return; /* 还不到下一个时刻，所以结束*/
 	}
 	timerctl.next = 0xffffffff;
-	for (i = 0; i < MAX_TIMER; i++) {
-		if (timerctl.timer[i].flags == TIMER_FLAGS_USING) {
-			if (timerctl.timer[i].timeout <= timerctl.count) {
-				 /* 超时 */
-				timerctl.timer[i].flags = TIMER_FLAGS_ALLOC;
-				fifo8_put(timerctl.timer[i].fifo, timerctl.timer[i].data);
-			}
-		} else {
-			 /* 还没有超时 */
-			if (timerctl.next > timerctl.timer[i].timeout) {
-				timerctl.next = timerctl.timer[i].timeout;
-			}
+	for (i = 0; i < timerctl.using; i++) {
+		/* timers的定时器都处于动作中，所以不确认flags */
+		if (timerctl.timers[i]->timeout > timerctl.count) {
+			break;
 		}
+		/* 超时*/
+		timerctl.timers[i]->flags = TIMER_FLAGS_ALLOC;
+		fifo8_put(timerctl.timers[i]->fifo, timerctl.timers[i]->data);
+	}
+	/* 正好有i个定时器超时了。其余的进行移位。 */
+	timerctl.using -= i;
+	for (j = 0; j < timerctl.using; j++) {
+		timerctl.timers[j] = timerctl.timers[i + j];
+	}
+	if (timerctl.using > 0) {
+		timerctl.next = timerctl.timers[0]->timeout;
+	} else {
+		timerctl.next = 0xffffffff;
 	}
 	return;
 }