diff --git a/src/common_code/common_code.cc b/src/common_code/common_code.cc
index 237a10c..2a3f273 100644
--- a/src/common_code/common_code.cc
+++ b/src/common_code/common_code.cc
@@ -47,6 +47,13 @@ CommonCode::CommonCode(const ShortCode &short_code) { // load from short code
     code = short_code.to_common_code().code;
 }
 
+std::ostream& operator<<(std::ostream &out, const CommonCode &self) {
+    char str[10];
+    sprintf(str, "%09lX", self.code);
+    out << str;
+    return out;
+}
+
 bool CommonCode::check(uint64_t common_code) { // whether common code is valid
     ///   M_1x1     M_1x2     M_2x1     M_2x2
     ///  1 0 0 0   1 1 0 0   1 0 0 0   1 1 0 0
diff --git a/src/common_code/common_code.h b/src/common_code/common_code.h
index 65f1cdc..abfab35 100644
--- a/src/common_code/common_code.h
+++ b/src/common_code/common_code.h
@@ -2,6 +2,7 @@
 
 #include <string>
 #include <cstdint>
+#include <ostream>
 #include "raw_code.h"
 #include "short_code.h"
 
@@ -16,7 +17,7 @@ public:
     std::string to_string(bool shorten = false) const;
 
     static bool check(uint64_t common_code);
-    // TODO: std::cout << CommonCode(...)
+    friend std::ostream& operator<<(std::ostream &out, const CommonCode &self);
 
     explicit CommonCode(uint64_t common_code);
     explicit CommonCode(const RawCode &raw_code);
diff --git a/src/main.cc b/src/main.cc
index 21f44bc..61454ec 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -360,6 +360,7 @@ int main() {
 //    std::cout << CommonCode(0x4FEA13400).to_string() << std::endl;
 
     printf("%09lX\n", CommonCode::from_string("1a9bf0c").unwrap());
+    std::cout << CommonCode("4feA134") << std::endl;
 
 //    std::cerr << (clock() - start_time) * 1000 / CLOCKS_PER_SEC << "ms" << std::endl;
     std::cerr << (clock() - start_time) * 1000000 / CLOCKS_PER_SEC << "us" << std::endl;