yea i know.. but turing is a funny language
here's what the documentation says:
An external declaration is used to access variables or subprograms that are written in other languages or which require special linkage. This feature is implementation-dependent and dangerous and may cause arbitrary data or program corruption. From an interpretive environment such as Turing, this provides linkage to items that are part of the Turing system. For compiled versions of Turing, the linkage would be by means of a standard, operating system-specific linkage editor.