# Turing (programming language)

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Turing is a Pascal-like programming language developed in 1982 by Ric Holt and James Cordy, then of University of Toronto, Canada. Turing is a descendant of Euclid, Pascal and SP/k that features a clean syntax and precise machine-independent semantics.

Named after British computer scientist Alan Turing, Turing is used primarily as a teaching language at the high school and university level. 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. Downloads can be found here Holt Software. Currently, Microsoft Windows is the only supported platform. Turing was, at one point, widely used in high schools in Ontario as an introduction to programming.[citation needed]

In 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.[1][2][3]

The makers of Turing, Holt Software Associates, have since ceased operations. It is unclear whether Turing is still in development, but there have been no new releases since November 25, 2007.[2]

## Contents

### Syntax

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)
```

## Open implementations

Currently, there are two open source alternative implementations of Turing, TPlus, a native compiler for the concurrent systems programming language variant Turing Plus, and OpenT, a new system currently under development. Open sourcing of the original complete Turing implementation from Holt Software is also currently underway.

### TPlus

TPlus is an open-source implementation of original (non-OO) Turing with systems programming extensions developed at the University of Toronto and ported to Linux, Solaris and Mac OS X at Queen's University in the late 1990s. TPlus implements Turing+ (Turing Plus), a concurrent systems programming language based the original Turing programming language. Some, but not all, of the features of Turing Plus were eventually subsumed into the present Object-Oriented Turing language. Turing Plus extends 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.

### OpenT

OpenT is an open-source language, compiler, and IDE being developed by the members of the dTeam of Computer Science Canada. It shares many similarities with Turing, and is fully backwards compatible with it. OpenT was originally begun to avoid the proprietary nature of Turing, although the original complete Holt Software Turing implementation is currently being transferred to open source.