in c what library is rand in
Perhaps your teacher wrote functions with these names for use in your class, or maybe you really mean random() and srandom() which are part of POSIX and not available on Windows. rand() and srand() are part of the standard library and will be provided by any standard conforming implementation of C++. You should avoid rand() and srand() and use the new C++11 <random> library. <random> was added as part of the C++11 standard (and VS2012 does provide it).