29 Numerics library [numerics]

29.6 Random number generation [rand]

29.6.9 Low-quality random number generation [c.math.rand]

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[ Note: The header <cstdlib> declares the functions described in this subclause.  — end note ]

int rand(); void srand(unsigned int seed);

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Effects: The rand and srand functions have the semantics specified in the C standard library.

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Remarks: The implementation may specify that particular library functions may call rand. It is implementation-defined whether the rand function may introduce data races ([res.on.data.races]). [ Note: The other random number generation facilities in this International Standard ([rand]) are often preferable to rand, because rand's underlying algorithm is unspecified. Use of rand therefore continues to be non-portable, with unpredictable and oft-questionable quality and performance.  — end note ]

See also: ISO C 7.22.2