Jacobian matrix and the Null pointer

[Brian Gough]

Haisam K. Ido writes:
 > What is the null pointer in the text below?
 > 
 > ref: http://sources.redhat.com/gsl/ref/gsl-ref_25.html#SEC379

There should be an explanation of what null pointers are in any
introductory book on C.

regards
-- 
Brian Gough

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