diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -38,6 +38,7 @@
 #include "utils.h"
 #include "defines.h"
 #include "version.h"
+#include "setting_defines.h"
 
 #if defined(Q_OS_WIN) && defined(QT_STATIC)
 #include <QtPlugin>
@@ -433,18 +434,18 @@ void MainWindow::loadAllSettings(QSettin
 void MainWindow::saveMWSettings(QSettings* settings)
 {
     // save window geometry
-    settings->beginGroup("MainWindow");
-    settings->setValue("size", size());
-    settings->setValue("pos", pos());
+    settings->beginGroup(SettingGroup_MainWindow);
+    settings->setValue(SG_MainWindow_Size, size());
+    settings->setValue(SG_MainWindow_Pos, pos());
     settings->endGroup();
 }
 
 void MainWindow::loadMWSettings(QSettings* settings)
 {
     // load window geometry
-    settings->beginGroup("MainWindow");
-    resize(settings->value("size", size()).toSize());
-    move(settings->value("pos", pos()).toPoint());
+    settings->beginGroup(SettingGroup_MainWindow);
+    resize(settings->value(SG_MainWindow_Size, size()).toSize());
+    move(settings->value(SG_MainWindow_Pos, pos()).toPoint());
     settings->endGroup();
 }
 
diff --git a/src/portcontrol.cpp b/src/portcontrol.cpp
--- a/src/portcontrol.cpp
+++ b/src/portcontrol.cpp
@@ -25,6 +25,8 @@
 #include <QLabel>
 #include <QMap>
 #include <QtDebug>
+
+#include "setting_defines.h"
 #include "utils.h"
 
 #define TBPORTLIST_MINWIDTH (200)
@@ -341,14 +343,13 @@ QString PortControl::currentFlowControlT
 
 void PortControl::saveSettings(QSettings* settings)
 {
-    settings->beginGroup("Port");
-    settings->setValue("selectedPort", selectedPortName());
-    settings->setValue("baudRate", ui->cbBaudRate->currentText());
-    settings->setValue("parity", currentParityText());
-    settings->setValue("dataBits", dataBitsButtons.checkedId());
-    settings->setValue("stopBits", stopBitsButtons.checkedId());
-    settings->setValue("flowControl", currentFlowControlText());
-
+    settings->beginGroup(SettingGroup_Port);
+    settings->setValue(SG_Port_SelectedPort, selectedPortName());
+    settings->setValue(SG_Port_BaudRate, ui->cbBaudRate->currentText());
+    settings->setValue(SG_Port_Parity, currentParityText());
+    settings->setValue(SG_Port_DataBits, dataBitsButtons.checkedId());
+    settings->setValue(SG_Port_StopBits, stopBitsButtons.checkedId());
+    settings->setValue(SG_Port_FlowControl, currentFlowControlText());
     settings->endGroup();
 }
 
@@ -357,10 +358,10 @@ void PortControl::loadSettings(QSettings
     // make sure the port is closed
     if (serialPort->isOpen()) togglePort();
 
-    settings->beginGroup("Port");
+    settings->beginGroup(SettingGroup_Port);
 
     // set port name if it exists in the current list otherwise ignore
-    QString portName = settings->value("selectedPort", QString()).toString();
+    QString portName = settings->value(SG_Port_SelectedPort, QString()).toString();
     if (!portName.isEmpty())
     {
         int index = portList.indexOfName(portName);
@@ -369,26 +370,26 @@ void PortControl::loadSettings(QSettings
 
     // load baud rate setting if it exists in baud rate list
     QString baudSetting = settings->value(
-        "baudRate", ui->cbBaudRate->currentText()).toString();
+        SG_Port_BaudRate, ui->cbBaudRate->currentText()).toString();
     int baudIndex = ui->cbBaudRate->findText(baudSetting);
     if (baudIndex > -1) ui->cbBaudRate->setCurrentIndex(baudIndex);
 
     // load parity setting
     QString parityText =
-        settings->value("parity", currentParityText()).toString();
+        settings->value(SG_Port_Parity, currentParityText()).toString();
     QSerialPort::Parity paritySetting = paritySettingMap.key(
         parityText, (QSerialPort::Parity) parityButtons.checkedId());
     parityButtons.button(paritySetting)->setChecked(true);
 
     // load number of bits
-    int dataBits = settings->value("dataBits", dataBitsButtons.checkedId()).toInt();
+    int dataBits = settings->value(SG_Port_Parity, dataBitsButtons.checkedId()).toInt();
     if (dataBits >=5 && dataBits <= 8)
     {
         dataBitsButtons.button((QSerialPort::DataBits) dataBits)->setChecked(true);
     }
 
     // load stop bits
-    int stopBits = settings->value("stopBits", stopBitsButtons.checkedId()).toInt();
+    int stopBits = settings->value(SG_Port_StopBits, stopBitsButtons.checkedId()).toInt();
     if (stopBits == QSerialPort::OneStop)
     {
         ui->rb1StopBit->setChecked(true);
@@ -400,7 +401,7 @@ void PortControl::loadSettings(QSettings
 
     // load flow control
     QString flowControlSetting =
-        settings->value("flowControl", currentFlowControlText()).toString();
+        settings->value(SG_Port_FlowControl, currentFlowControlText()).toString();
     if (flowControlSetting == "hardware")
     {
         ui->rbHardwareControl->setChecked(true);
diff --git a/src/setting_defines.h b/src/setting_defines.h
new file mode 100644
--- /dev/null
+++ b/src/setting_defines.h
@@ -0,0 +1,42 @@
+/*
+  Copyright © 2016 Hasan Yavuz Özderya
+
+  This file is part of serialplot.
+
+  serialplot is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  serialplot is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with serialplot.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef SETTING_DEFINES_H
+#define SETTING_DEFINES_H
+
+const char SettingGroup_MainWindow[] = "MainWindow";
+const char SettingGroup_Port[] = "Port";
+const char SettingGroup_DataFormat[] = "DataFormat";
+const char SettingGroup_Channels[] = "Channels";
+const char SettingGroup_Plot[] = "Plot";
+const char SettingGroup_Commands[] = "Commands";
+
+// mainwindow setting keys
+const char SG_MainWindow_Size[] = "size";
+const char SG_MainWindow_Pos[] = "pos";
+
+// port setting keys
+const char SG_Port_SelectedPort[] = "selectedPort";
+const char SG_Port_BaudRate[] = "baudRate";
+const char SG_Port_Parity[] = "parity";
+const char SG_Port_DataBits[] = "dataBits";
+const char SG_Port_StopBits[] = "stopBits";
+const char SG_Port_FlowControl[] = "flowControl";
+
+#endif // SETTING_DEFINES_H