Input of Structures by means of SMILES strings

SMILES is a simple, concise and rather readable molecular structure specification format. It is (incompletely) published in
D. Weininger, SMILES, a Chemical Language and Information System. 1. Introduction to Methodology and Encoding Rules, J. Chem. Inf. Comput. Sci. 1988, 28, 31-36.

Daylight has a SMILES WWW tutorial online.

The basic syntax rules are:

The SMILES conversion routine behind the 3D coordinate service will accept some SMILES strings which are strictly speaking syntactically incorrect, but are still resolvable (i.e. allow ring closure numbers after bond order indicators, or ignore case of atoms not resolvable as pi-centers). The decoder also understands a number of local, but compatible SMILES syntax extensions such atom lists, etc..