Synthetic biology is the construction of artificial biological systems, such as programmable cells, using principles from engineering, electronics, computer science and computational biology. Using biological circuit, we can produce a new concentration gradient that has twice the frequency. If 1 is represented by a concentration of the chemical within the threshold, and a 0 is represented by a concentration outside the threshold, then we can represent any two digit binary number. Thus, we can differentiate separate regions at certain distances away from a point source. The focus of these early studies was on using digital models as a way of understanding events in the living cell. The Boolean approximation was a way of avoiding an unwieldy analysis of a complex chemical web. To follow all those molecular interactions in complete detail would have required tracking the concentrations of innumerable molecular species, measuring the rates of chemical reactions, and solving hundreds of coupled differential equations. Either pretending that every gene is on or off reduced the problem to a simpler digital abstraction.