update words.md

thu_os/chp18.md

@@ -35,3 +35,4 @@ public:
 为了实现信号量，主要就是需要实现它的两个成员函数`down`和`up`。
 
 当一个进程请求资源时，首先应该检查`sem`当前的值，如果`sem > 0`，表示系统还有剩余的资源，则执行`--sem`并且将资源分配给请求进程；如果`sem <= 0`，则表示当前系统已经没有这种资源了，仍然执行`--sem`，表示新增了一个进程在等待这个资源。由于当前进程得不到它请求的资源，此时应该释放CPU的控制权，调度其他进程进入运行状态。为了在资源空闲时可以唤醒当前进程，可以对每个信号量新增一个等待队列，并且将等待该信号量的进程加入等待队列中。
+

words.md

@@ -817,7 +817,7 @@ Some Words
 	- It is unlikely that a record company would enforce its views on an established artists.
 
 + statute
-> (n)a law passed by a council, parliament etc and formally written down</bt>
+> (n)a law passed by a council, parliament etc and formally written down</br>
 > (n)a formal rule of an institution or organization
 
 	- Protection for the consumer is laid down by statute.
@@ -875,4 +875,27 @@ Some Words
 > (v)to perform a story or play by acting
 
 	- The authorities have failed so far to enact a law allowing unrestricted emigration.
+	- a project that is to be enacted next year
 	- She often enacted the stories told to her by her father.
+
+## 24th, Sep
+
++ demographics
+> (n)the number and characteristics of people who live in a particular area or form a particular group, especially in relation to their age, how much money they have and what they spend it on
+
+	- The demographics of the country have changed dramatically in recent years.
+	- demographic change
+
++ stem
+> (v)to stop something from happening, spreading, or developing.</br>
+> (V)to stop the flow of liquid
+
+	- The measures are meant to stem the tide of illegal immigration.
+	- an attempt to stem the decline in profits
+	- A tight bandage should stem the bleeding.
+
++ up in arms
+> angry or upset
+
+	- The union is up in arms over the reduction in health benefits.
+