CPU bug fixes and Simulator enhancements.

Bug Fixes:

- Fixed several bugs in the CPU that caused processor status flags to
  be set incorrectly.  Instructions affected were: STA, STX, STY, CMP,
  CPX, CPY, BIT.

- Made some internal-use-only methods on the CPU class private.

- Fixed incorrect disassembly of (Indirect,X) and (Indirect),Y
  instructions. Although this didn't affect behavior, it certainly
  caused me some confusion in debugging.

- Added missing "BCS" instruction to instruction table.

Enhancements:

- Now includes a full version of Lee Davison's Enhanced 6502 BASIC
  bundled as source code and a ROM image. Get that REAL COMPUTER
  EXPERIENCE!(tm)

- If a file named "rom.bin" exists in the same directory where the
  simulator is executed, it will be loaded at addresses $d000-$ffff.

- Gave the CPU an idle loop to make simulated timing a little more
  realistic (but this is still an area needing major improvement)

- Changed the CPU's toString() method to give better debugging output.

- Added a small typeahead buffer to the Console.

- Better exception messaging.

Misc:

- Bumped version to 0.5, updated README.

src/main/java/com/loomcom/symon/devices/Memory.java

@@ -1,9 +1,12 @@
 package com.loomcom.symon.devices;
 
+import java.io.*;
 import java.util.*;
 
 import com.loomcom.symon.exceptions.*;
 
+import javax.swing.*;
+
 public class Memory extends Device {
 
     private boolean readOnly;
@@ -24,6 +27,17 @@ public class Memory extends Device {
         this(address, size, false);
     }
 
+    public static Memory makeROM(int address, int size, File f) throws MemoryRangeException, IOException {
+        Memory memory = new Memory(address, size, true);
+        memory.loadFromFile(f);
+        return memory;
+    }
+
+    public static Memory makeRAM(int address, int size) throws MemoryRangeException {
+        Memory memory = new Memory(address, size, false);
+        return memory;
+    }
+
     public void write(int address, int data) throws MemoryAccessException {
         if (readOnly) {
             throw new MemoryAccessException("Cannot write to read-only memory at address " + address);
@@ -32,6 +46,34 @@ public class Memory extends Device {
         }
     }
 
+    /**
+     * Load the memory from a file.
+     *
+     * @param file The file to read an array of bytes from.
+     * @throws MemoryRangeException if the file and memory size do not match.
+     * @throws IOException if the file read fails.
+     */
+    public void loadFromFile(File file) throws MemoryRangeException, IOException {
+        if (file.canRead()) {
+            long fileSize = file.length();
+
+            if (fileSize > mem.length) {
+                throw new MemoryRangeException("File will not fit in available memory.");
+            } else {
+                int i = 0;
+                FileInputStream fis = new FileInputStream(file);
+                BufferedInputStream bis = new BufferedInputStream(fis);
+                DataInputStream dis = new DataInputStream(bis);
+                while (dis.available() != 0) {
+                    mem[i++] = dis.readUnsignedByte();
+                }
+            }
+        } else {
+            throw new IOException("Cannot open file " + file);
+        }
+
+    }
+
     public int read(int address) throws MemoryAccessException {
         return this.mem[address];
     }
@@ -40,7 +82,6 @@ public class Memory extends Device {
         Arrays.fill(this.mem, val);
     }
 
-
     public String toString() {
         return "Memory: " + getMemoryRange().toString();
     }