Turing (programming language)

Named after British computer scientist Alan Turing, Turing is used primarily as a teaching language at the high school and university level.[1] Two other versions exist, Object-Oriented Turing and Turing Plus, a systems programming variant. In September 2001, "Object Oriented Turing" was renamed "Turing" and the original Turing was renamed "Classic Turing". Turing is no longer supported by Holt Software Associates in Toronto, Ontario. Currently, Microsoft Windows is the only supported platform. Turing is widely used in high schools in Ontario as an introduction to programming.[2]

On November 28, 2007, Turing, which was previously a commercial programming language, became freeware, available to download from the developer's website free of charge for personal, commercial, and educational use.[3][4][5]

The makers of Turing, Holt Software Associates, have since ceased operations, and Turing has seen no further development since November 25, 2007.[4]

Turing is designed to have a very lightweight, readable, intuitive syntax. Here is the entire Hello World! program in Turing with syntax highlighting:

put "Hello World!"

Turing avoids semicolons and braces, using explicit end markers for most language constructs instead, and allows declarations anywhere. Here is a complete program defining and using the traditional recursive function to calculate a factorial.

 % Accepts a number and calculates its factorial
 
 function factorial (n: int) : real
      if n = 0 then
           result 1
      else
           result n * factorial (n - 1)
      end if
 end factorial
 
 var n: int
 loop
      put "Please input an integer: " ..
      get n
      exit when n >= 0
      put "Input must be a non-negative integer."
 end loop
 
 put "The factorial of ", n, " is ", factorial (n)

Currently, there are two open source alternative implementations of Turing: Open Turing, an open source version of the original interpreter, and TPlus, a native compiler for the concurrent systems programming language variant Turing Plus. OpenT, a project to develop a compiler for Turing, is no longer in development.

As an addition to the usual graphics drawing functions, Turing features special functions for drawing maple leaves to allow easier drawing of the Canadian flag.[8]

Turing+ (Turing Plus) is a concurrent systems programming language based on the Turing programming language designed by James Cordy and Ric Holt, then at the University of Toronto, Canada, in 1987. Some, but not all, of the features of Turing+ were eventually subsumed into Object-Oriented Turing. Turing+ extended original Turing with processes and monitors (as specified by C.A.R. Hoare) as well as language constructs needed for systems programming such as binary input-output, separate compilation, variables at absolute addresses, type converters and other features.

Turing+ was explicitly designed to replace Concurrent Euclid in systems-programming applications. The TUNIS operating system, originally written in Concurrent Euclid, was recoded to Turing+ in its MiniTunis implementation. Turing+ has been used to implement several production software systems, including the TXL programming language.

Object-Oriented Turing is an extension of the Turing programming language and a replacement for Turing Plus created by Ric Holt[9][10] of the University of Toronto, Canada, in 1991. It is imperative, object-oriented, and concurrent. It has modules, classes, single inheritance, processes, exception handling, and optional machine-dependent programming.

There is an integrated development environment under the X Window System and a demo version. Versions exist for Sun-4, MIPS, RS-6000, NeXTSTEP, Windows 95 and others.

• Euclid (programming language)
• Concurrent Euclid
• TXL

• Holt, Richard C; Cordy, James R (December 1983). "The Turing language report". Annual Progress Report. Canada: Computer Systems Research Institute, University of Toronto. ISSN 0316-6295.
• Holt, Richard C; Cordy, James R (December 1988). "The Turing programming language". Communications of the ACM. 31 (12): 1410–1423. doi:10.1145/53580.53581. S2CID 40859457.
• Holt, Richard C; Matthews, Philip A; Rosselet, J Alan; Cordy, James R (1988). The Turing programming language: design and definition. Englewood Cliffs, N.J.: Prentice Hall. ISBN 978-0-13-933136-7. OCLC 17377539.
• Grogono, Peter (1995). Programming with Turing and Object Oriented Turing. Springer-Verlag. ISBN 978-0-387-94517-0.

Wikibooks has a book on the topic of: Turing

• Forum for Turing Help, Tutorials, & Source Code
• Github page for the Open Turing project