diff --git a/day5/d2.cpp b/day5/d2.cpp
new file mode 100644
index 0000000..784141b
--- /dev/null
+++ b/day5/d2.cpp
@@ -0,0 +1,14 @@
+// 无符号数
+#include <iostream>
+#include <bitset>
+
+using namespace std;
+
+int main()
+{
+    unsigned char a = 255, b = 0, c = 0x30;
+    cout << bitset<8>(a) << "," << dec << (int)a << endl;
+    cout << bitset<8>(b) << "," << dec << (int)b << endl;
+    cout << bitset<8>(c) << "," << dec << (int)c << endl;
+    return 0;
+}
\ No newline at end of file