From 2ef6f492c474cb12b2cd535c6ca69be993dcbf95 Mon Sep 17 00:00:00 2001
From: simon <Anise5-humid5-Allow-5Lulu-Honk>
Date: Sat, 30 Dec 2017 11:14:45 -0500
Subject: [PATCH] Fixes #64

---
 .../assembly/instruction/NegInstruction.java   | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/Server/src/main/java/net/simon987/server/assembly/instruction/NegInstruction.java b/Server/src/main/java/net/simon987/server/assembly/instruction/NegInstruction.java
index 14b6316..c9638b0 100644
--- a/Server/src/main/java/net/simon987/server/assembly/instruction/NegInstruction.java
+++ b/Server/src/main/java/net/simon987/server/assembly/instruction/NegInstruction.java
@@ -14,7 +14,23 @@ public class NegInstruction extends Instruction {
 
     @Override
     public Status execute(Target dst, int dstIndex, Status status) {
-        dst.set(dstIndex, -dst.get(dstIndex));
+        //If the operand is zero, the carry flag is cleared; in all other cases, the carry flag is set.
+
+        char destination = (char) dst.get(dstIndex);
+
+        if (destination == 0) {
+            status.setCarryFlag(false);
+            status.setZeroFlag(true);
+        } else {
+            status.setCarryFlag(true);
+        }
+
+        //Attempting to negate a word containing -32,768 causes no change to the operand and sets the Overflow Flag.
+        if (destination == 0x8000) {
+            status.setOverflowFlag(true);
+        } else {
+            dst.set(dstIndex, -destination);
+        }
 
         return status;
     }