diff --git a/ch2/.idea/misc.xml b/ch2/.idea/misc.xml
deleted file mode 100644
index 56189180..00000000
--- a/ch2/.idea/misc.xml
+++ /dev/null
@@ -1,22 +0,0 @@
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diff --git a/ch2/.idea/user.iml b/ch2/.idea/user.iml
deleted file mode 100644
index b44d0258..00000000
--- a/ch2/.idea/user.iml
+++ /dev/null
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diff --git a/ch2/.idea/vcs.xml b/ch2/.idea/vcs.xml
deleted file mode 100644
index 6c0b8635..00000000
--- a/ch2/.idea/vcs.xml
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diff --git a/ch2/.idea/workspace.xml b/ch2/.idea/workspace.xml
deleted file mode 100644
index b4ed534b..00000000
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diff --git a/ch3-coop/.idea/misc.xml b/ch3-coop/.idea/misc.xml
deleted file mode 100644
index 56189180..00000000
--- a/ch3-coop/.idea/misc.xml
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diff --git a/ch3-coop/.idea/user.iml b/ch3-coop/.idea/user.iml
deleted file mode 100644
index b44d0258..00000000
--- a/ch3-coop/.idea/user.iml
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diff --git a/ch3-coop/.idea/vcs.xml b/ch3-coop/.idea/vcs.xml
deleted file mode 100644
index 6c0b8635..00000000
--- a/ch3-coop/.idea/vcs.xml
+++ /dev/null
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\ No newline at end of file
diff --git a/ch3-coop/.idea/workspace.xml b/ch3-coop/.idea/workspace.xml
deleted file mode 100644
index b4ed534b..00000000
--- a/ch3-coop/.idea/workspace.xml
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diff --git a/ch3/.idea/misc.xml b/ch3/.idea/misc.xml
deleted file mode 100644
index 56189180..00000000
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diff --git a/ch3/README.md b/ch3/README.md
new file mode 100644
index 00000000..f68848ac
--- /dev/null
+++ b/ch3/README.md
@@ -0,0 +1,19 @@
+# Tutorial 第三章测试用例 part2
+
+在第三章第二阶段中，需要在第一阶段的基础上实现一个抢占式调度的分时多任务系统。在 `src/bin` 目录下，我们可以找到四个应用程序：
+
+* ``00power_3``
+* ``01power_5``
+* ``02power_7``
+* ``03sleep``
+
+像第一阶段一样，它们也需要被加载到不同的物理地址处运行。
+
+应用被设计为运行在用户模式，批处理系统应运行在监督模式，它们都直接访问物理内存。
+
+这一阶段需要实现的系统调用：
+
+* `sys_get_time`：获取系统当前的毫秒数，在应用 `03sleep` 中使用，可以简单估计所有应用运行的总时间。
+
+阅读应用程序代码可知，三个 `power` 应用分别计算一个质数的幂次对另一个大质数取模的余数，由于次数很高在一个时间片之内无法完成，而它们又不会使用 `sys_yield` 主动交出 CPU 使用权，因此只能由内核进行强制切换。
+
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diff --git a/ch4/README.md b/ch4/README.md
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index 00000000..f72b720f
--- /dev/null
+++ b/ch4/README.md
@@ -0,0 +1,3 @@
+# Tutorial 第四章测试用例
+
+第四章的应用与第三章第二阶段的应用一样，只是它们均被链接到 0x0 开头的地址空间上。这就需要我们利用 CPU 提供的页表机制，为每个应用创造一个虚拟地址空间。
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