diff --git a/ch5/ch5-cpu4/src/main.rs b/ch5/ch5-cpu4/src/main.rs
index 6fc0db65..006f1f2f 100644
--- a/ch5/ch5-cpu4/src/main.rs
+++ b/ch5/ch5-cpu4/src/main.rs
@@ -59,14 +59,14 @@ impl CPU {
     }
 
     fn se(&mut self, vx: u8, kk: u8) {
-        if vx == kk {
+        if self.registers[vx as usize] == kk {
             self.position_in_memory += 2;
         }
     }
 
     /// () SNE  **S**tore if **n**ot **e**qual 
     fn sne(&mut self, vx: u8, kk: u8) {
-        if vx != kk {
+        if self.registers[vx as usize] != kk {
             self.position_in_memory += 2;
         }
     }
@@ -102,9 +102,10 @@ impl CPU {
 
     // (7xkk)
     fn add_xy(&mut self, x: u8, y: u8) {
-        self.registers[x as usize] += self.registers[y as usize];
-
-        // TODO: SET CARRY FLAG!!!!
+        /// Set carry flag
+        let (wrapped, is_overflow) = self.registers[x as usize].overflowing_add(self.registers[y as usize]);
+        self.registers[0xF] = if is_overflow {1} else {0};
+        self.registers[x as usize] = wrapped;
     }
 
     fn and_xy(&mut self, x: u8, y: u8) {
@@ -154,4 +155,4 @@ fn main() {
     assert_eq!(cpu.registers[0], 45);
 
     println!("5 + (10 * 2) + (10 * 2) = {}", cpu.registers[0]);
-}
\ No newline at end of file
+}