diff --git a/24_day/bootpack.h b/24_day/bootpack.h
index 4215c38..bc14ac9 100644
--- a/24_day/bootpack.h
+++ b/24_day/bootpack.h
@@ -176,7 +176,8 @@ void sheet_free(struct SHEET *sht);
 #define MAX_TIMER		500
 struct TIMER {
 	struct TIMER *next;
-	unsigned int timeout, flags;
+	unsigned int timeout;
+	char flags, flags2; 
 	struct FIFO32 *fifo;
 	int data;
 };
@@ -192,6 +193,8 @@ void timer_free(struct TIMER *timer);
 void timer_init(struct TIMER *timer, struct FIFO32 *fifo, int data);
 void timer_settime(struct TIMER *timer, unsigned int timeout);
 void inthandler20(int *esp);
+int timer_cancel(struct TIMER *timer);
+void timer_cancelall(struct FIFO32 *fifo);
 
 /* mtask.c */
 #define MAX_TASKS 1000	/*最大任务数量*/
diff --git a/24_day/console.c b/24_day/console.c
index d61d65c..ab3f80a 100644
--- a/24_day/console.c
+++ b/24_day/console.c
@@ -308,6 +308,7 @@ int cmd_app(struct CONSOLE *cons, int *fat, char *cmdline)
 					sheet_free(sht); /*关闭*/
 				}
 			}
+			timer_cancelall(&task->fifo);
 			memman_free_4k(memman, (int) q, segsiz);
 		} else {
 			cons_putstr0(cons, ".hrb file format error.\n");
@@ -421,6 +422,7 @@ int *hrb_api(int edi, int esi, int ebp, int esp, int ebx, int edx, int ecx, int
 		}
 	} else if (edx == 16) { 
 		reg[7] = (int) timer_alloc();
+		((struct TIMER *) reg[7])->flags2 = 1; /*允许自动取消*/
 	} else if (edx == 17) {
 		timer_init((struct TIMER *) ebx, &task->fifo, eax + 256);
 	} else if (edx == 18) {
diff --git a/24_day/timer.c b/24_day/timer.c
index 2c795f8..9018ac8 100644
--- a/24_day/timer.c
+++ b/24_day/timer.c
@@ -36,6 +36,7 @@ struct TIMER *timer_alloc(void)
 	for (i = 0; i < MAX_TIMER; i++) {
 		if (timerctl.timers0[i].flags == 0) {
 			timerctl.timers0[i].flags = TIMER_FLAGS_ALLOC;
+			timerctl.timers0[i].flags2 = 0;
 			return &timerctl.timers0[i];
 		}
 	}
@@ -116,3 +117,53 @@ void inthandler20(int *esp)
 	}
 	return;
 }
+
+int timer_cancel(struct TIMER *timer)
+{
+	int e;
+	struct TIMER *t;
+	e = io_load_eflags();
+	io_cli(); /*在设置过程中禁止改变定时器状态*/
+	if (timer->flags == TIMER_FLAGS_USING) { /*是否需要取消？*/
+		if (timer == timerctl.t0) {
+			/*第一个定时器的取消处理*/
+			t = timer->next;
+			timerctl.t0 = t;
+			timerctl.next = t->timeout;
+		} else {
+			/*非第一个定时器的取消处理*/
+			/*找到timer前一个定时器*/
+			t = timerctl.t0;
+			for (;;) {
+				if (t->next == timer) {
+					break;
+				}
+				t = t->next;
+			}
+			t->next = timer->next; 
+			/*将之前“timer的下一个”指向“timer的下一个”*/
+		}
+		timer->flags = TIMER_FLAGS_ALLOC;
+		io_store_eflags(e);
+		return 1; /*取消处理成功*/
+	}
+	io_store_eflags(e);
+	return 0; /*不需要取消处理*/
+}
+
+void timer_cancelall(struct FIFO32 *fifo)
+{
+	int e, i;
+	struct TIMER *t;
+	e = io_load_eflags();
+	io_cli(); /*在设置过程中禁止改变定时器状态*/
+	for (i = 0; i < MAX_TIMER; i++) {
+		t = &timerctl.timers0[i];
+		if (t->flags != 0 && t->flags2 != 0 && t->fifo == fifo) {
+			timer_cancel(t);
+			timer_free(t);
+		}
+	}
+	io_store_eflags(e);
+	return;
+}