A digital design compiler and simulator to produce and test designs based on a Lola circuit description. Invented by Niklaus Wirth (designer of Pascal and many other languages) Lola is similar to other high-level circuit design languages like VHDL and Verilog except much simpler to learn and use.
For example, here's the design of a 4-bit binary counter:
MODULE Counter0 (IN clk: BIT; OUT d: [4] BIT);
REG (clk) R: [4] BIT;
BEGIN
R := {R.3 ^ R.3 & R.2 & R.1 & R.0, (* R.3 *)
R.2 ^ R.2 & R.1 & R.0, (* R.2 *)
R.1 ^ R.1 & R.0, (* R.1 *)
~R.0}; (* R.0 *)
d := R
END Counter0.