README.md

README.md

@@ -1,3 +1,34 @@
 # forsus
-
 Pure chemical compounds database and general API.
+
+`forsus` provides a simple API to read `json` files containing pure component
+information and later on use it inside other projects.
+
+## The basics
+Using `forsus` in your Fortran project is relatively simple:
+
+All the readable parameters are kept on a `Substance` object, from which
+they can be later on extracted.
+
+It keeps a global variable `forsus_dir` with should be the path of your database
+file directory. [data/json](data/json) is the directory that the library uses by
+default.
+
+```fortran
+use forsus
+
+type(Substance) :: s
+
+! This will use the default path
+s = Substance("1-butanol")
+
+! This will use the defined path
+forsus_dir = "my/json/files"
+s = Substance("1-butanol")
+
+! It is also possible to use a custom path
+sus = Substance("1-butanol", path="the/json/is/here")
+
+! Show the critical temperature
+print *, sus%critical%critical_temperature%value
+```