Technically is an expression language with a very simple syntax. A and a are different symbols and would refer to different variables.
Elementary commands consist of either expressions or assignments .
If an expression is given as a command, it is evaluated, printed, and the value is lost. An assignment also evaluates an expression and passes the value to a variable but the result is not automatically printed. This prompt may be changed by the user. In these notes, we will generally omit the continuation prompt and indicate continuation by simple indenting.