If Hello World is inadequate, what canonical program would better serve to demonstrate the salient features of a programming language?

    Must it use variables?
    Must it have flow control?
    Must it actually compute something?
    Must it use non-primitive data structures?
    Must it exhibit use of the language’s code organisation features?

These are some of the more generic properties that programs can have.

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One suggestion (from David Pearce) was Conway’s Game of Life: a simple simulation of finite automata. This seems like a good demonstration of most of the properties.

http://ejrh.wordpress.com/2012/05/10/beyond-hello-world/