diff --git a/Lab3/Lab3 b/Lab3/Lab3
deleted file mode 100755
index ad3c598..0000000
Binary files a/Lab3/Lab3 and /dev/null differ
diff --git a/Lab4/Lab4 b/Lab4/Lab4
new file mode 100755
index 0000000..4f3e1aa
Binary files /dev/null and b/Lab4/Lab4 differ
diff --git a/Lab4/drawbase.h b/Lab4/drawbase.h
new file mode 100644
index 0000000..0a9d8fa
--- /dev/null
+++ b/Lab4/drawbase.h
@@ -0,0 +1,21 @@
+#ifndef DRAWBASE_H
+#define DRAWBASE_H
+
+// forward reference
+class GraphicsContext;
+
+class DrawingBase
+{
+	public:
+		// prevent warnings
+		virtual ~DrawingBase(){}
+		virtual void paint(GraphicsContext* gc){}
+		virtual void keyDown(GraphicsContext* gc, unsigned int keycode){}
+		virtual void keyUp(GraphicsContext* gc, unsigned int keycode){}
+		virtual void mouseButtonDown(GraphicsContext* gc, 
+								unsigned int button, int x, int y){}
+		virtual void mouseButtonUp(GraphicsContext* gc,
+								unsigned int button, int x, int y){}
+		virtual void mouseMove(GraphicsContext* gc, int x, int y){}
+};
+#endif
\ No newline at end of file
diff --git a/Lab4/gcontext.cpp b/Lab4/gcontext.cpp
new file mode 100644
index 0000000..b091b77
--- /dev/null
+++ b/Lab4/gcontext.cpp
@@ -0,0 +1,26 @@
+/* This is an abstract base class representing a generic graphics
+ * context.  Most implementation specifics will need to be provided by
+ * a concrete implementation.  See header file for specifics. */
+
+#define _USE_MATH_DEFINES	// for M_PI
+#include <cmath>	// for trig functions
+#include "gcontext.h"	
+
+/*
+ * Destructor - does nothing
+ */
+GraphicsContext::~GraphicsContext()
+{
+	// nothing to do
+	// here to insure subclasses handle destruction properly
+}
+
+//does nothing
+void GraphicsContext::drawLine(int x0, int y0, int x1, int y1){}
+void GraphicsContext::drawCircle(int x0, int y0, unsigned int radius){}
+
+
+void GraphicsContext::endLoop()
+{
+	run = false;
+}
\ No newline at end of file
diff --git a/Lab4/gcontext.h b/Lab4/gcontext.h
new file mode 100644
index 0000000..61c6713
--- /dev/null
+++ b/Lab4/gcontext.h
@@ -0,0 +1,141 @@
+#ifndef GCONTEXT_H
+#define GCONTEXT_H
+
+/**
+ * This class is intended to be the abstract base class
+ * for a graphical context for various platforms.  Any
+ * concrete subclass will need to implement the pure virtual
+ * methods to support setting pixels, getting pixel color,
+ * setting the drawing mode, and running an event loop to
+ * capture mouse and keyboard events directed to the graphics
+ * context (or window).  Specific expectations for the various
+ * methods are documented below.
+ * 
+ * */    
+
+
+// forward reference - needed because runLoop needs a target for events
+class DrawingBase;
+
+
+class GraphicsContext
+{
+	public:
+		/*********************************************************
+		 * Some constants and enums
+		 *********************************************************/
+		// This enumerated type is an argument to setMode and allows
+		// us to support two different drawing modes.  MODE_NORMAL is
+		// also call copy-mode and the affect pixel(s) are set to the 
+		// color requested.  XOR mode will XOR the new color with the
+		// existing color so that the change is reversible.		
+		enum drawMode {MODE_NORMAL, MODE_XOR};
+	
+		// Some colors - for fun
+		static const unsigned int BLACK = 0x000000;
+		static const unsigned int BLUE = 0x0000FF;
+		static const unsigned int GREEN = 0x00FF00;
+		static const unsigned int RED = 0xFF0000;
+		static const unsigned int CYAN = 0x00FFFF;
+		static const unsigned int MAGENTA = 0xFF00FF;
+		static const unsigned int YELLOW = 0xFFFF00;
+		static const unsigned int GRAY = 0x808080;
+		static const unsigned int WHITE = 0xFFFFFF;
+	
+	
+		/*********************************************************
+		 * Construction / Destruction
+		 *********************************************************/
+		// Implementations of this class should include a constructor
+		// that creates the drawing canvas (window), sets a background
+		// color (which may be configurable), sets a default drawing
+		// color (which may be configurable), and start with normal
+		// (copy) drawing mode.
+	
+		// need a virtual destructor to ensure subclasses will have
+		// their destructors called properly.  Must be virtual.
+		virtual ~GraphicsContext();
+
+		/*********************************************************
+		 * Drawing operations
+		 *********************************************************/
+		
+		// Allows the drawing mode to be changed between normal (copy)
+		// and xor.  The implementing context should default to normal. 
+		virtual void setMode(drawMode newMode) = 0;
+
+		// Set the current color.  Implementations should default to white.
+		// color is 24-bit RGB value
+		virtual void setColor(unsigned int color) = 0;
+
+		// Set pixel to the current color
+		virtual void setPixel(int x, int y) = 0;
+		
+		// Get 24-bit RGB pixel color at specified location
+		// unsigned int will likely be 32-bit on 32-bit systems, and
+		// possible 64-bit on some 64-bit systems.  In either case,
+		// it is large enough to hold a 16-bit color.
+		virtual unsigned int getPixel(int x, int y) = 0;
+
+		// This should reset entire context to the current background
+		virtual void clear()=0;
+
+		// These are the naive implementations that use setPixel,
+		// but are overridable should a context have a better-
+		// performing version available.
+
+		 /* will need to be provided by the concrete
+		 * implementation.
+		 * 
+		 * Parameters:
+		 * 	x0, y0 - origin of line
+		 *  x1, y1 - end of line
+		 * 
+		 * Returns: void
+		 */
+		virtual void drawLine(int x0, int y0, int x1, int y1);
+		
+		/* will need to be provided by the concrete
+		 * implementation.
+		 * 
+		 * Parameters:
+		 * 	x0, y0 - origin/center of circle
+		 *  radius - radius of circle
+		 * 
+		 * Returns: void
+		 */
+		virtual void drawCircle(int x0, int y0, unsigned int radius);
+
+
+		/*********************************************************
+		 * Event loop operations
+		 *********************************************************/
+		
+		// Run Event loop.  This routine will receive events from
+		// the implementation and pass them along to the drawing.  It
+		// will return when the window is closed or other implementation-
+		// specific sequence.
+		virtual void runLoop(DrawingBase* drawing) = 0;
+		
+		// This method will end the current loop if one is running
+		// a default version is supplied
+		virtual void endLoop();
+
+
+		/*********************************************************
+		 * Utility operations
+		 *********************************************************/
+		
+		// returns the width of the window
+		virtual int getWindowWidth() = 0;
+		
+		// returns the height of the window
+		virtual int getWindowHeight() = 0;
+		
+	protected:
+		// this flag is used to control whether the event loop
+		// continues to run.
+		bool run;
+};
+
+#endif
\ No newline at end of file
diff --git a/Lab4/main.cpp b/Lab4/main.cpp
new file mode 100644
index 0000000..d7a712a
--- /dev/null
+++ b/Lab4/main.cpp
@@ -0,0 +1,28 @@
+#include "x11context.h"
+#include <unistd.h>
+#include <iostream>
+ 
+int main(void)
+{
+	GraphicsContext* gc = new X11Context(800,600,GraphicsContext::BLACK);
+ 
+ 
+	// draw some lines
+	gc->setColor(GraphicsContext::GREEN);
+	gc->setPixel(10,10);
+	gc->setPixel(30,30);
+	gc->drawLine(100,100,500,500);
+	gc->setColor(GraphicsContext::RED);
+	gc->drawLine(100,500,500,500);
+	gc->setColor(GraphicsContext::BLUE);
+	gc->drawLine(500,500,500,100);
+	gc->setColor(GraphicsContext::YELLOW);
+	gc->drawLine(500,100,100,100);
+	gc->setColor(GraphicsContext::MAGENTA);
+	gc->drawCircle(300,300,200);
+	sleep(10);
+ 
+	delete gc;
+ 
+	return 0;
+}
\ No newline at end of file
diff --git a/Lab4/makefile b/Lab4/makefile
new file mode 100644
index 0000000..0de43e1
--- /dev/null
+++ b/Lab4/makefile
@@ -0,0 +1,25 @@
+# lab4 Makefile
+
+CC = g++
+CFLAGS = -c -MMD -g
+LFLAGS = -lX11
+# Change w/ every new project
+SOURCES = main.cpp gcontext.cpp x11context.cpp
+OBJECTS = $(SOURCES:.cpp=.o)
+# Change w/ every new project
+EXECUTABLE = Lab4
+
+all: $(EXECUTABLE) $(SOURCES)
+
+$(EXECUTABLE): $(OBJECTS)
+	$(CC) -o $@ $(OBJECTS) $(LFLAGS)
+
+-include *.d
+
+%.o:%.cpp
+	$(CC) $(CFLAGS) $<
+
+clean:
+	rm -f $(EXECUTABLE)
+	rm -f $(OBJECTS)
+	rm -f *.d
\ No newline at end of file
diff --git a/Lab4/x11context.cpp b/Lab4/x11context.cpp
new file mode 100644
index 0000000..bc8f0d1
--- /dev/null
+++ b/Lab4/x11context.cpp
@@ -0,0 +1,239 @@
+/* Provides a simple drawing context for X11/XWindows
+ * You must have the X11 dev libraries installed.  If missing,
+ * 'sudo apt-get install libx11-dev' should help.
+ */
+
+#include <X11/Xlib.h> // Every Xlib program must include this
+#include <X11/Xutil.h> // needed for XGetPixel
+#include <X11/XKBlib.h> // needed for keyboard setup
+#include "x11context.h"
+#include "drawbase.h"
+#include <iostream>
+
+/**
+ * The only constructor provided.  Allows size of window and background
+ * color be specified.
+ * */
+X11Context::X11Context(unsigned int sizex=400,unsigned int sizey=400,
+						unsigned int bg_color=GraphicsContext::BLACK)
+{
+	// Open the display
+	display = XOpenDisplay(NULL);
+	
+	// Holding a key in gives repeated key_press commands but only
+	// one key_release
+	int supported;
+	
+	XkbSetDetectableAutoRepeat(display,true,&supported);
+
+	// Create a window - we will assume the color map is in RGB mode.  
+	window = XCreateSimpleWindow(display, DefaultRootWindow(display), 0, 0, 
+				 sizex, sizey, 0, 0 , bg_color);
+
+	// Sign up for MapNotify events
+	XSelectInput(display, window, StructureNotifyMask);
+
+	// Put the window on the screen
+	XMapWindow(display, window);
+
+	// Create a "Graphics Context"
+	graphics_context = XCreateGC(display, window, 0, NULL);
+
+	// Default color to white
+	XSetForeground(display, graphics_context, GraphicsContext::WHITE);
+
+	// Wait for MapNotify event
+	for(;;) 
+	{
+		XEvent e;
+		XNextEvent(display, &e);
+		if (e.type == MapNotify)
+		break;
+	}
+
+	// We also want exposure, mouse, and keyboard events
+	XSelectInput(display, window, ExposureMask|
+								ButtonPressMask|
+								ButtonReleaseMask|
+								KeyPressMask|
+								KeyReleaseMask|
+								PointerMotionMask);
+
+	// We need this to get the WM_DELETE_WINDOW message from the
+	// window manager in case user click the X icon
+	Atom atomKill = XInternAtom(display, "WM_DELETE_WINDOW", False);
+	XSetWMProtocols(display, window, &atomKill, 1);
+
+	return;
+}
+
+// Destructor  - shut down window and connection to server
+X11Context::~X11Context()
+{
+	XFreeGC(display, graphics_context);
+	XDestroyWindow(display,window);
+	XCloseDisplay(display);
+}
+
+// Set the drawing mode - argument is enumerated
+void X11Context::setMode(drawMode newMode)
+{
+	if (newMode == GraphicsContext::MODE_NORMAL)
+	{
+		XSetFunction(display,graphics_context,GXcopy);
+	}
+	else
+	{
+		XSetFunction(display,graphics_context,GXxor);
+	}
+}
+
+// Set drawing color - assume colormap is 24 bit RGB
+void X11Context::setColor(unsigned int color)
+{
+	// Go ahead and set color here - better performance than setting
+	// on every setPixel 
+    XSetForeground(display, graphics_context, color);
+}
+
+// Set a pixel in the current color
+void X11Context::setPixel(int x, int y)
+{
+	XDrawPoint(display, window, graphics_context, x, y);
+	XFlush(display);
+}
+
+unsigned int X11Context::getPixel(int x, int y)
+{
+	XImage *image;
+	image = XGetImage (display, window, x, y, 1, 1, AllPlanes, XYPixmap);
+	XColor color;
+	color.pixel = XGetPixel (image, 0, 0);
+	XFree (image);
+	XQueryColor (display, DefaultColormap(display, DefaultScreen (display)),
+					&color);
+	// I now have RGB values, but, they are 16 bits each, I only want 8-bits
+	// each since I want a 24-bit RGB color value
+	unsigned int pixcolor = color.red & 0xff00;
+	pixcolor |= (color.green >> 8);
+	pixcolor <<= 8;
+	pixcolor |= (color.blue >> 8);
+	return pixcolor;
+}
+
+void X11Context::clear()
+{
+	XClearWindow(display, window);
+	XFlush(display);
+}
+
+ 
+
+// Run event loop
+void X11Context::runLoop(DrawingBase* drawing)
+{
+	run = true;
+	
+	while(run)
+	{
+		XEvent e;
+		XNextEvent(display, &e);
+
+		// Exposure event - lets not worry about region
+		if (e.type == Expose)
+			drawing->paint(this);
+
+		// Key Down
+		else if (e.type == KeyPress)
+			drawing->keyDown(this,XLookupKeysym((XKeyEvent*)&e,
+					(((e.xkey.state&0x01)&&!(e.xkey.state&0x02))||
+					(!(e.xkey.state&0x01)&&(e.xkey.state&0x02)))?1:0));
+	 
+		// Key Up
+		else if (e.type == KeyRelease){
+			drawing->keyUp(this,XLookupKeysym((XKeyEvent*)&e,
+					(((e.xkey.state&0x01)&&!(e.xkey.state&0x02))||
+					(!(e.xkey.state&0x01)&&(e.xkey.state&0x02)))?1:0));
+				}
+
+		// Mouse Button Down
+		else if (e.type == ButtonPress)
+			drawing->mouseButtonDown(this,
+			e.xbutton.button,
+			e.xbutton.x,
+			e.xbutton.y);
+			
+		// Mouse Button Up
+		else if (e.type == ButtonRelease)
+			drawing->mouseButtonUp(this,
+			e.xbutton.button,
+			e.xbutton.x,
+			e.xbutton.y);
+			
+		// Mouse Move	
+		else if (e.type == MotionNotify)
+			drawing->mouseMove(this,
+			e.xmotion.x,
+			e.xmotion.y);
+
+		// This will respond to the WM_DELETE_WINDOW from the
+		// window manager.
+		else if (e.type == ClientMessage)
+		break;
+	}
+}
+
+
+int X11Context::getWindowWidth()
+{
+	XWindowAttributes window_attributes;
+	XGetWindowAttributes(display,window, &window_attributes);
+	return window_attributes.width;
+}
+
+int X11Context::getWindowHeight()
+{
+	XWindowAttributes window_attributes;
+	XGetWindowAttributes(display,window, &window_attributes);
+	return window_attributes.height;
+}
+
+// void X11Context::drawLine(int x1, int y1, int x2, int y2)
+// {
+// 	XDrawLine(display, window, graphics_context, x1, y1, x2, y2);		
+// 	XFlush(display);
+// }
+	
+// Bresenham Implementation
+void X11Context::drawLine(int x1, int y1, int x2, int y2){
+	//setPixel(x1,y1);
+	// Check direction of line
+	if(abs(y2-y1) < abs(x2-x1)){
+		if(x1 > x2){
+			//swap
+		} else {
+			//swap
+		}
+	} else {
+
+	}
+	int dx = x2-x1;
+	int dy = y2-y1;
+	int D = 2*dy-dx;
+	int y = y1;
+	for(int i = x1; i < x2; i++){
+		setPixel(i,y);
+		if(D > 0){
+			y = y+1;
+			D = D-2*dx;
+		}
+		D = D+2*dy;
+	}
+}
+
+void X11Context::drawCircle(int x, int y, unsigned int radius)
+{
+	XDrawArc(display, window, graphics_context, x-radius,
+				 y-radius, radius*2, radius*2, 0, 360*64);
+	XFlush(display);
+}
\ No newline at end of file
diff --git a/Lab4/x11context.h b/Lab4/x11context.h
new file mode 100644
index 0000000..54a7af1
--- /dev/null
+++ b/Lab4/x11context.h
@@ -0,0 +1,49 @@
+#ifndef X11_CONTEXT
+#define X11_CONTEXT
+/**
+ * This class is a sample implementation of the GraphicsContext class
+ * for the X11 / XWindows system.
+ * */    
+ 
+#include <X11/Xlib.h>   // Every Xlib program must include this
+#include "gcontext.h"	// base class
+
+class X11Context : public GraphicsContext
+{
+	public:
+		// Default Constructor
+		X11Context(unsigned int sizex,unsigned int sizey,unsigned int bg_color);
+
+		// Destructor
+		virtual ~X11Context();
+		
+		// Drawing Operations
+		void setMode(drawMode newMode);
+		void setColor(unsigned int color);
+		void setPixel(int x, int y);
+		unsigned int getPixel(int x, int y);
+		void clear();
+		//void drawLine(int x1, int y1, int x2, int y2);
+		void drawLine(int x1, int y1, int x2, int y2);
+		void drawCircle(int x, int y, unsigned int radius);
+
+
+		// Event looop functions
+		void runLoop(DrawingBase* drawing);		
+		
+		// we will use endLoop provided by base class
+		
+		// Utility functions
+		int getWindowWidth();
+		int getWindowHeight();
+		
+
+	private:
+		// X11 stuff - specific to this context
+		Display* display;
+		Window window;
+		GC graphics_context;
+
+};
+
+#endif
\ No newline at end of file