Compilare: user.cpp: In function ‘int main()’: user.cpp:31: warning: NULL used in arithmetic user.cpp:42: warning: NULL used in arithmetic user.cpp:57: warning: comparison between signed and unsigned integer expressions user.cpp:65: warning: comparison between signed and unsigned integer expressions user.cpp:72: warning: comparison between signed and unsigned integer expressions user.cpp:80: warning: format ‘%ld’ expects type ‘long int’, but argument 2 has type ‘size_t’ user.cpp:82: warning: comparison between signed and unsigned integer expressions user.cpp:20: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result