diff --git a/day4/d10.cpp b/day4/d10.cpp
new file mode 100644
index 0000000..17d3a22
--- /dev/null
+++ b/day4/d10.cpp
@@ -0,0 +1,15 @@
+#include <iostream>
+
+using namespace std;
+
+int main()
+{
+    char c = 'a'; // 1B
+    int m = 2;    // 4B
+    // 小字节转大字节, 会自动转换
+    m += c; // 先将c转换为int,再相加
+    cout << "m = " << m << endl;
+    // 大字节转小字节,会丢失精度,需要强制类型转换
+    cout << "m to char is " << (char)m << endl;
+    return 0;
+}
\ No newline at end of file
diff --git a/day4/d8.cpp b/day4/d8.cpp
new file mode 100644
index 0000000..8fc5fd9
--- /dev/null
+++ b/day4/d8.cpp
@@ -0,0 +1,13 @@
+#include <iostream>
+
+using namespace std;
+
+int main()
+{
+    int x1, y1, x2, y2;
+    cout << "请输入两个点坐标, 格式如 x1 y1 x2 y2" << endl;
+    cin >> x1 >> y1 >> x2 >> y2;
+    cout << "P1(" << x1 << "," << y1 << ")"
+         << " P2(" << x2 << "," << y2 << ")" << endl;
+    return 0;
+}
\ No newline at end of file