diff --git a/gcode.cpp b/gcode.cpp
index 1d66457..930d8e3 100644
--- a/gcode.cpp
+++ b/gcode.cpp
@@ -37,12 +37,12 @@ pair<char, double> extract_argument(const string& str)
 	return result;
 }
 
-void gcode_dummy(const vector<string>&, TimeCalc&, double&)
+void gcode_dummy(const vector<string>&, TimeCalc&, double&, bool&)
 {
 }
 
 // Linear Move
-void g1(const vector<string>& line_tokens, TimeCalc& calc, double& speed)
+void g1(const vector<string>& line_tokens, TimeCalc& calc, double& speed, bool& is_absolute)
 {
 	double result;
 	vector<string>::const_iterator it;
@@ -62,7 +62,14 @@ void g1(const vector<string>& line_tokens, TimeCalc& calc, double& speed)
 		// Extruder
 		case 'E':
 		case 'e':
-			pos.e = arg.second;
+			if (is_absolute)
+			{
+				pos.e = arg.second;
+			}
+			else
+			{
+				pos.e += arg.second;
+			}
 			break;
 
 		// Feedrate (Speed) in units/min
@@ -78,17 +85,38 @@ void g1(const vector<string>& line_tokens, TimeCalc& calc, double& speed)
 
 		case 'X':
 		case 'x':
-			pos.x = arg.second;
+			if (is_absolute)
+			{
+				pos.x = arg.second;
+			}
+			else
+			{
+				pos.x += arg.second;
+			}
 			break;
 
 		case 'Y':
 		case 'y':
-			pos.y = arg.second;
+			if (is_absolute)
+			{
+				pos.y = arg.second;
+			}
+			else
+			{
+				pos.y += arg.second;
+			}
 			break;
 
 		case 'Z':
 		case 'z':
-			pos.z = arg.second;
+			if (is_absolute)
+			{
+				pos.z = arg.second;
+			}
+			else
+			{
+				pos.z += arg.second;
+			}
 			break;
 
 		default:
@@ -101,7 +129,7 @@ void g1(const vector<string>& line_tokens, TimeCalc& calc, double& speed)
 }
 
 // Dwell
-void g4(const vector<string>& line_tokens, TimeCalc& calc, double& speed)
+void g4(const vector<string>& line_tokens, TimeCalc& calc, double& speed, bool& is_absolute)
 {
 	double result;
 	vector<string>::const_iterator it;
@@ -137,7 +165,7 @@ void g4(const vector<string>& line_tokens, TimeCalc& calc, double& speed)
 }
 
 // Move to Origin (Home)
-void g28(const vector<string>& line_tokens, TimeCalc& calc, double& speed)
+void g28(const vector<string>& line_tokens, TimeCalc& calc, double& speed, bool& is_absolute)
 {
 	Point pos = calc.get_pos();
 
@@ -148,8 +176,20 @@ void g28(const vector<string>& line_tokens, TimeCalc& calc, double& speed)
 	calc.set_pos(pos);
 }
 
+// Set to Absolute Positioning
+void g90(const vector<string>& line_tokens, TimeCalc& calc, double& speed, bool& is_absolute)
+{
+	is_absolute = true;
+}
+
+// Set to Relative Positioning
+void g91(const vector<string>& line_tokens, TimeCalc& calc, double& speed, bool& is_absolute)
+{
+	is_absolute = false;
+}
+
 // Set Position
-void g92(const vector<string>& line_tokens, TimeCalc& calc, double& speed)
+void g92(const vector<string>& line_tokens, TimeCalc& calc, double& speed, bool& is_absolute)
 {
 	vector<string>::const_iterator it;
 	pair<char, double> arg;
diff --git a/gcode.h b/gcode.h
index a6520fa..611b48e 100644
--- a/gcode.h
+++ b/gcode.h
@@ -11,15 +11,17 @@ using namespace std;
 
 
 // Typedef of the function pointer
-typedef void (*gcode_cmd_t)(const vector<string>&, TimeCalc&, double&);
+typedef void (*gcode_cmd_t)(const vector<string>&, TimeCalc&, double&, bool& is_absolute);
 
 // Always returns 0 sec
-void gcode_dummy(const vector<string>&, TimeCalc&, double&);
+void gcode_dummy(const vector<string>&, TimeCalc&, double&, bool&);
 
 // All handled gcode commands
-void g1(const vector<string>& line_tokens, TimeCalc& calc, double& speed);
-void g4(const vector<string>& line_tokens, TimeCalc& calc, double& speed);
-void g28(const vector<string>& line_tokens, TimeCalc& calc, double& speed);
-void g92(const vector<string>& line_tokens, TimeCalc& calc, double& speed);
+void g1(const vector<string>& line_tokens, TimeCalc& calc, double& speed, bool& is_absolute);
+void g4(const vector<string>& line_tokens, TimeCalc& calc, double& speed, bool& is_absolute);
+void g28(const vector<string>& line_tokens, TimeCalc& calc, double& speed, bool& is_absolute);
+void g90(const vector<string>& line_tokens, TimeCalc& calc, double& speed, bool& is_absolute);
+void g91(const vector<string>& line_tokens, TimeCalc& calc, double& speed, bool& is_absolute);
+void g92(const vector<string>& line_tokens, TimeCalc& calc, double& speed, bool& is_absolute);
 
 #endif // GCODE_H_
diff --git a/main.cpp b/main.cpp
index 9a1b61c..4f70322 100644
--- a/main.cpp
+++ b/main.cpp
@@ -92,8 +92,11 @@ void init_map(map<string, gcode_cmd_t>& gcode_map)
 	gcode_map["G28"] = g28;
 	gcode_map["g28"] = g28;
 
-	gcode_map["G90"] = gcode_dummy;
-	gcode_map["g90"] = gcode_dummy;
+	gcode_map["G90"] = g90;
+	gcode_map["g90"] = g90;
+
+	gcode_map["G91"] = g91;
+	gcode_map["g91"] = g91;
 
 	gcode_map["G92"] = g92;
 	gcode_map["g92"] = g92;
@@ -259,6 +262,7 @@ int main(int argc, char **argv)
 
 	TimeCalc calc;
 	double speed;
+	bool is_absolute = true;
 	double total_time;
 	int hours;
 	int minutes;
@@ -289,7 +293,7 @@ int main(int argc, char **argv)
 
 			if (0 != gcode_map.count(line_tokens[0]))
 			{
-				gcode_map[line_tokens[0]](line_tokens, calc, speed);
+				gcode_map[line_tokens[0]](line_tokens, calc, speed, is_absolute);
 			}
 			else
 			{