Blue is a free system for teaching object-oriented programming, developed in Monash University. It is an integrated development environment (IDE) and a programming language. Blue has been used for teaching since 1997. The development was stopped in 1999 when one of its principals, Michael Kölling, began applying the IDE design to the Java programming language, resulting in BlueJ.

The Blue language syntax is derived from the Eiffel programming language and one of the most useful developments for instruction was the integrated development environment which was designed with learning object-oriented programming in mind. The Blue IDE visually shows the reference and inheritance relationships between classes. At run time it allows the developer to visually and interractively create instances of any class, inspect the instance, and invoke functions on those classes.

Many of the language features it has inherited from Eiffel make it suitable for teaching, such as design by contract (pre-conditions, post-conditions, class invariants) and automatic garbage collection.

The team that developed Blue has continued on with a very similar integrated development environment called BlueJ which uses the Java programming language and has similar goals. The BlueJ project is under active development.

External links

• The Blue Page - Teaching Object Oriented Programming
• The Blue Page - Blue Language Specification
• The Blue Page - Blue Environment Manual