diff --git a/day6/d7.cpp b/day6/d7.cpp
new file mode 100644
index 0000000..4abc219
--- /dev/null
+++ b/day6/d7.cpp
@@ -0,0 +1,13 @@
+#include <iostream>
+
+using namespace std;
+
+int main()
+{
+    int n = 10;
+    cout << "~10 = " << ~n << endl; // -11 : ~ 位非运算符: 二进制取反: 0000 1010 => 1111 0101 => -11
+    n = -9;
+    cout << "~(-9) = " << ~n << endl; // 8 : ~ 位非运算符: 二进制取反: 1000 1001 => 0111 0110 => 8
+
+    return 0;
+}
\ No newline at end of file