On BSD on the VAX, address 0 used to happen to hold 0, so dereferencing NULL got you zero. That was at the time a sufficiently popular platform that some progra

On BSD on the VAX, address 0 used to happen to hold 0, so dereferencing NULL got you zero. That was at the time a sufficiently popular platform that some programs assumed the behaviour (eg, that a null pointer could be used as an empty string), and you can still find older docs on the web exhorting the reader to avoid "all the world's a VAX" syndrome.