diff --git a/day5/d1.cpp b/day5/d1.cpp
new file mode 100644
index 0000000..62082c2
--- /dev/null
+++ b/day5/d1.cpp
@@ -0,0 +1,23 @@
+// 源码反码补码
+#include <iostream>
+#include <bitset>
+
+using namespace std;
+
+int main()
+{
+    int z = -9;
+    cout << bitset<8>(z) << endl;
+    cout << bitset<8>(z >> 1) << endl; // 右移一位，符号位不变，左边补1
+    cout << bitset<8>(z << 1) << endl; // 左移一位，符号位不变，右边补0
+    cout << dec << z << endl;          // 十进制
+    cout << oct << z << endl;          // 八进制
+    cout << hex << z << endl;          // 十六进制
+
+    signed int x = 20;
+    cout << bitset<8>(x) << endl;
+    cout << bitset<8>(x >> 1) << endl; // 右移一位，符号位不变，左边补0
+    cout << bitset<8>(x << 1) << endl; // 左移一位，符号位不变，右边补0
+
+    return 0;
+}
\ No newline at end of file