diff --git a/device.cpp b/device.cpp
index 0955063..3410c44 100644
--- a/device.cpp
+++ b/device.cpp
@@ -5,21 +5,17 @@
 
 using namespace std;
 
-Device::Device(FtdiJtag *jtag, enum prog_mode mode, string filename):
-		_filename(filename), _mode(mode)
+Device::Device(FtdiJtag *jtag, string filename):
+		_filename(filename),
+		_file_extension(filename.substr(filename.find_last_of(".") +1)),
+		_mode(NONE_MODE)
 {
 	_jtag = jtag;
+	cout << _file_extension << endl;
 }
 
-int Device::idCode()
-{
-	return 0;
-}
+Device::~Device() {}
 
-void Device::program()
-{
-	throw std::runtime_error("Not implemented");
-}
 void Device::reset()
 {
 	throw std::runtime_error("Not implemented");
diff --git a/device.hpp b/device.hpp
index 5e1a158..bcfce42 100644
--- a/device.hpp
+++ b/device.hpp
@@ -17,13 +17,15 @@ class Device {
 			SPI_MODE,
 			MEM_MODE
 		};
-		Device(FtdiJtag *jtag, enum prog_mode, std::string filename);
-		virtual void program();
-		int  idCode();
-		void reset();
+		Device(FtdiJtag *jtag, std::string filename);
+		virtual ~Device();
+		virtual void program(unsigned int offset = 0) = 0;
+		virtual int  idCode() = 0;
+		virtual void reset();
 	protected:
 		FtdiJtag *_jtag;
 		std::string _filename;
+		std::string _file_extension;
 		enum prog_mode _mode;
 };