diff --git a/lesson#19.4 - this, alias, alias this keyword/main.d b/lesson#19.4 - this, alias, alias this keyword/main.d
new file mode 100644
index 0000000..3057b89
--- /dev/null
+++ b/lesson#19.4 - this, alias, alias this keyword/main.d	
@@ -0,0 +1,46 @@
+// ****** this, alias, alias ... this keywords  ******
+
+// Converting Celcius to Fahrenheit
+class CelciusToFahrenheit {
+	float celcius;
+	
+	// init
+	this(float celcius) {
+		this.celcius = celcius;
+	}
+
+	// convert to Fahrenheit
+	double convert() {
+		return double(9.0/5.0 * celcius + 32.0);
+	}
+	
+	// enable automatic conversion of CelciusToFahrenheit objects to double
+	alias convert this;
+}
+
+// print temperature announcement for the day
+void announce(string day, double temp) {
+	import std.stdio: writeln;
+	
+	writeln("Temperature for ", day, " is ", temp, "F.");
+}
+
+void main() {
+	CelciusToFahrenheit monday = new CelciusToFahrenheit(36.0);
+	announce("Monday", monday);
+	
+	// creating an alias of CelciusToFahrenheit class	
+	// similar to 'typedef' in C, 'using' in C++11
+	alias CtoF = CelciusToFahrenheit; // also: alias CelciusToFahrenheit CtoF;
+
+	CtoF tuesday = new CtoF(24.5);
+	announce("Tuesday", tuesday);
+
+	// imitating rust's data types:
+	alias u8 = ubyte;
+	alias u16 = ushort;
+	alias u32 = uint;
+	alias f32 = float;
+	alias f64 = double;
+	// etc...
+}