The simplified molecular-input line-entry system or SMILES is a specification in form of a line notation for describing the structure of chemical molecules using short ASCII strings.

The term SMILES refers to a line notation for encoding molecular structures and specific instances should strictly be called SMILES strings.

Aromatic nitrogen bonded to hydrogen, as found in pyrrole must be represented as and imidazole is written in SMILES notation as n1ccc1.

They can express more information than the simpler SMILES notation and differ in that every structure has a unique InChI string, which is important in database applications.

The original SMILES specification was developed by Arthur Weininger and David Weininger in the late 1980s.

Two popular formats are SMILES and InChI.

Generation of SMILES: Break cycles, then write as branches off a main backbone.

SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules.

The Environmental Protection Agency funded the initial project to develop SMILES.

SMILES is generally considered to have the advantage of being slightly more human-readable than InChI ; it also has a wide base of software support with extensive theoretical ( e. g., graph theory ) backing.

However, the term SMILES is also commonly used to refer to both a single SMILES string and a number of SMILES strings ; the exact meaning is usually apparent from the context.

The terms Canonical and Isomeric can lead to some confusion when applied to SMILES.

The terms describe different attributes of SMILES strings and are not mutually exclusive.

Typically, a number of equally valid SMILES can be written for a molecule.

Algorithms have been developed to ensure the same SMILES is generated for a molecule regardless of the order of atoms in the structure.

This SMILES is unique for each structure, although dependent on the canonicalization algorithm used to generate it, and is termed the Canonical SMILES.

These algorithms first convert the SMILES to an internal representation of the molecular structure and do not simply manipulate strings as is sometimes thought.

Various algorithms for generating Canonical SMILES have been developed, including those by Daylight Chemical Information Systems, OpenEye Scientific Software, MEDIT, Chemical Computing Group, MolSoft LLC, and the Chemistry Development Kit.

A common application of Canonical SMILES is indexing and ensuring uniqueness of molecules in a database.

These are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed Isomeric SMILES.

By allowing the radix point to be adjustable, floating-point notation allows calculations over a wide range of magnitudes, using a fixed number of digits, while maintaining good precision.

Operator overloading is claimed to be useful because it allows the developer to program using notation " closer to the target domain " and allows user-defined types a similar level of syntactic support as types built into the language.

Once analyzed, a statement in prefix notation becomes less intimidating to the human mind as it allows some separation from convention with added convenience.

To simplify this problem, computer scientists have adopted Big O notation, which allows functions to be compared in a way that ensures that particular aspects of a machine's construction do not need to be considered, but rather only the asymptotic behavior as problems become large.

The compact notation allows many defaults and abbreviations for common cases.

B. F. Skinner, noted psychologist, commented on medical notation as a form of multiple audience control, which allows the doctor to communicate to the pharmacist things which might be opposed by the patient if they could understand it.

The complexity of this notation allows numbers to be written in many different ways, and Fibonacci described several methods for converting from one style of representation to another.

It has a graphical notation and allows for extension with a Profile ( UML ).

The Iverson bracket allows the equivalent notation,, to be used instead of

The tetration notation allows us to make these diagrams slightly simpler while still employing a geometric representation ( we could call these tetration towers ).

Standard mathematical notation allows a formal definition of range.

* Encoding Control Notation, a standard notation that allows the specification of custom encoding rules for ASN. 1 types

Index notation allows indication of the elements of the array by simply writing a < sub > i </ sub >, where the index i is known to run from 1 to n.

The notation allows a clear generalization to multi-dimensional arrays of elements: tensors.

This allows the user to score parts using traditional notation, using the graphic notation of the piano roll and to record acoustic or electronic instruments in real time along side the existing scores.

SCORE is known for its ability to precisely position symbols on the page, and also allows the user complete control over every aspect of their music through making every possible aspect of music notation manually controllable ( this, however, also leads to some difficulty or frustration of use in the program ).

A VPL allows programming with visual expressions, spatial arrangements of text and graphic symbols, used either as elements of syntax or secondary notation.

The multi-index notation allows the extension of many formulae from elementary calculus to the corresponding multi-variable case.

Its generalization to binary notation allows to use it in a computer.

This kind of notation allows the use of quantum field theoretic techniques to be used in the analysis of reaction diffusion systems.

When a cubic graph is Hamiltonian, LCF notation allows it to be represented concisely.

This notation allows us to define the velocity of the points A and B as