diff --git a/src/04_UDEF/Testat/Testat.cpp b/src/04_UDEF/Testat/main_04_UDEF_e.cpp
similarity index 91%
rename from src/04_UDEF/Testat/Testat.cpp
rename to src/04_UDEF/Testat/main_04_UDEF_e.cpp
index 87f2c41..b2884fe 100644
--- a/src/04_UDEF/Testat/Testat.cpp
+++ b/src/04_UDEF/Testat/main_04_UDEF_e.cpp
@@ -8,10 +8,12 @@ struct BinaryOctet {
     bool evenParity;
     char bitsAsDigits[bitsPerOctet]{};
 
+
     BinaryOctet(int x = 0);
     BinaryOctet(const BinaryOctet&) = default;
     const BinaryOctet operator--(int);
     const BinaryOctet operator++(int);
+    BinaryOctet operator~();
     bool operator!=(BinaryOctet &a);
     bool operator>=(BinaryOctet &a);
     BinaryOctet operator-(BinaryOctet a);
@@ -51,6 +53,14 @@ const BinaryOctet BinaryOctet::operator++(int) {
     return operator+(*new BinaryOctet(1));
 }
 
+BinaryOctet BinaryOctet::operator~() {
+    BinaryOctet res;
+    for(int i = 0; i <= bitsPerOctet; i++) {
+        res.bitsAsDigits[i] = bitsAsDigits[i] == '0' ? '1' : '0';
+    }
+    return res;
+}
+
 BinaryOctet BinaryOctet::operator+(BinaryOctet a) {
     BinaryOctet result;
     bool over = false;
@@ -177,6 +187,15 @@ std::ostream &operator<<(std::ostream &os, BinaryOctet *toBePrinted) {
     return os;
 }
 
+void printInverse(int i) {
+    std::cout << ~i << std::endl;
+}
+
+
+void printInverse(BinaryOctet o) {
+    std::cout << ~o << std::endl;
+}
+
 
 int main(int argc, char **argv) {
     std::cout << "=========   init   ==========" << std::endl;
@@ -205,5 +224,9 @@ int main(int argc, char **argv) {
     d--;
     std::cout << "11111111-- = " << d-- << std::endl;
 
+    std::cout << "========   printInverse   ============" << std::endl;
+    printInverse(42);
+    printInverse(b);
+
     return 0;
 }
\ No newline at end of file
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 6397d9a..4fd107a 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -10,7 +10,7 @@ add_executable(03_FLOW_Testat 03_FLOW/Testat/main_mp2_FLOW_a.cpp helpers/AnsiCon
 
 add_executable(04_UDEF_MP 04_UDEF/MP/main_04_UDEF_e.cpp)
 target_link_libraries(04_UDEF_MP m)
-add_executable(04_UDEF_Testat 04_UDEF/Testat/Testat.cpp)
+add_executable(04_UDEF_Testat 04_UDEF/Testat/main_04_UDEF_e.cpp)
 target_link_libraries(04_UDEF_Testat m)
 
 add_executable(05_OO_MP 05_OO/MP/shapes_main.cpp helpers/AnsiConsole.cpp 05_OO/MP/Shape.cpp 05_OO/MP/Position.h 05_OO/MP/Shape.h 05_OO/MP/Point.cpp 05_OO/MP/Point.h 05_OO/MP/Circle.cpp 05_OO/MP/Circle.h 05_OO/MP/Rectangle.cpp 05_OO/MP/Rectangle.h 05_OO/MP/Scene.cpp 05_OO/MP/Scene.h)