diff --git a/src/interpreter/interpreter.rs b/src/interpreter/interpreter.rs
index 8962e08..5029f0b 100644
--- a/src/interpreter/interpreter.rs
+++ b/src/interpreter/interpreter.rs
@@ -358,25 +358,39 @@ impl Interpreter {
                 /*
                  * INC
                  */
-                Mnemonic::INC_Reg(reg) => self
-                    .computer
-                    .regs
-                    .write(reg, self.computer.regs.read(reg) + 1),
-                Mnemonic::INC_Mod(target) => {
-                    let val = self.computer.read_modrm(target)?;
-                    self.computer.write_modrm(target, val + 1)?
+                Mnemonic::INC_Reg(reg) => {
+                    let cf = self.computer.flags.cf;
+                    let dest = ModRmTarget::Register(reg);
+                    let src = ArithmeticOperand::Immediate(ImmediateOperand::Byte(1));
+                    self.computer.add(dest, src)?;
+                    // The CF flag is not affected
+                    self.computer.flags.cf = cf;
+                }
+                Mnemonic::INC_Mod(dest) => {
+                    let cf = self.computer.flags.cf;
+                    let src = ArithmeticOperand::Immediate(ImmediateOperand::Byte(1));
+                    self.computer.add(dest, src)?;
+                    // The CF flag is not affected
+                    self.computer.flags.cf = cf;
                 }
 
                 /*
                  * DEC
                  */
-                Mnemonic::DEC_Reg(reg) => self
-                    .computer
-                    .regs
-                    .write(reg, self.computer.regs.read(reg) - 1),
-                Mnemonic::DEC_Mod(target) => {
-                    let val = self.computer.read_modrm(target)?;
-                    self.computer.write_modrm(target, val - 1)?
+                Mnemonic::DEC_Reg(reg) => {
+                    let cf = self.computer.flags.cf;
+                    let dest = ModRmTarget::Register(reg);
+                    let src = ArithmeticOperand::Immediate(ImmediateOperand::Byte(1));
+                    self.computer.sub(dest, src)?;
+                    // The CF flag is not affected
+                    self.computer.flags.cf = cf;
+                }
+                Mnemonic::DEC_Mod(dest) => {
+                    let cf = self.computer.flags.cf;
+                    let src = ArithmeticOperand::Immediate(ImmediateOperand::Byte(1));
+                    self.computer.sub(dest, src)?;
+                    // The CF flag is not affected
+                    self.computer.flags.cf = cf;
                 }
 
                 /*
@@ -624,8 +638,17 @@ impl Interpreter {
                         .write_modrm(target, !self.computer.read_modrm(target)?)?;
                 }
                 Mnemonic::NEG(target) => {
-                    let val = !self.computer.read_modrm(target)?;
-                    self.computer.write_modrm(target, val + 0b1)?;
+                    let lhs = !self.computer.read_modrm(target)?;
+                    let rhs = ImmediateOperand::Byte(1);
+                    let result = lhs + rhs;
+                    self.computer.flags.cf = result < self.computer.read_modrm(target)?;
+                    self.computer.flags.of =
+                        (lhs.msb() && rhs.msb()) && (result.msb() != lhs.msb());
+                    self.computer.flags.zf = result.zero();
+                    self.computer.flags.sf = result.msb();
+                    self.computer.flags.pf = result.parity();
+
+                    self.computer.write_modrm(target, result)?;
                 }
 
                 /*