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Icon Programming Language

Icon is a very high-level programming language featuring goal-directed execution and many facilities for managing strings and textual patterns. It is related to SNOBOL and SL5, string processing languages. Icon is not object-oriented, but an object-oriented extension called Idol was developed in 1996 which eventually became Unicon.

Icon's most important capabilities are:

  • support for strings of characters of arbitrary length

  • high-level facilities for analyzing strings

  • a powerful expression-evaluation mechanism

  • sophisticated data structures for managing complex relationships among data

  • high-level graphics facilities

  • automatic storage management


procedure doSomething(aString)


procedure main ()
      write ( "Hello world!" );


Hello World!


Icon is a high-level, imperative, procedural language especially useful for processing strings and structures.

  • String processing capabilities - allow a multitude of operations on strings, including convenient analysis of strings using pattern matching functions.

  • Expression-evaluation syntax - uses control structures to combine evaluations with backtracking.

  • Built-in data structures - data types can be numerical values, strings, lists, characters, records, procedure, or tables with associative lookup. Lists can be used as stacks and queues, records, or vectors.

  • Strongly typed language - values are typed, as opposed to variables. Values are not statically typed.

  • Transparent automatic type conversion - values are converted to expected types without casting.

  • Storage allocation automatic - Objects are created during execution and deallocated as space is needed. String sizes do not need to be defined when program is coded and are dependent only on available memory.

  • Graphics facilities


  • Artificial Intelligence

  • Research Applications

  • Expert Systems

  • Prototyping Tool

  • Symbolic Mathematics

  • Text Processing:

1. Text Analysis

2. Text Editing

3. Text Generation

4. Document Formatting

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