An early Dutch computer: Willem Bartjens

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Willem Bartjens was the author of an arithmetic textbook 'Cyferringe' (Arithmetic) famous - or notorious? - in the Netherlands. It was reprinted many times during two centuries: first appearing in 1637, the last edition was printed in 1839. Bartjens' name is still quoted in phrases expressing the obviousness of a result, like 'According to Bartjens, two and two makes four'.

Bartjens was a 'computer' in the original meaning of the word, i.e. a person doing computations. Therefore the game on the back of the Computer Museum's copy of Cyfferinge is an early example of a computer game! The game (a simple example of a magic square) is shown below.
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Rephrased in modern language, the text runs as follows:

"In conclusion, an amusing computation which always gives 24 whether the numbers are added along a diagonal, a row or a column.
For any other desired sum x, first compute y = x/3, then enter the following numbers in row order in the fields of the square: y+3, y-2, y-1, y-4, y, y+4, y+1, y+2, y-3.

Having done well was all my heart's desire: is it not as it should be, my heart will be hurt.

The End"