added description

Author: m2sfpa

README.md

@@ -1,2 +1,7 @@
 # M2-Syntax-Diagrams
-Syntax diagrams for the M2C, M2J and M2Sharp compiler suite.
+
+This repository contains common syntax diagrams for the M2C, M2J and M2Sharp compiler suite.
+
+The syntax diagrams are automatically generated by a TCL/TK script and exported to PNG format.
+
+For the repositories of the compilers, see [M2J](https://github.com/m2sf/m2j) and [M2Sharp](https://github.com/m2sf/m2sharp).