Compilare: user.cpp: In function ‘void back()’: user.cpp:25: warning: statement has no effect user.cpp: In function ‘int main()’: user.cpp:78: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:79: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:80: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:83: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result In file included from /usr/include/stdio.h:910, from /usr/include/c++/4.4/cstdio:45, from user.cpp:1: In function ‘char* gets(char*)’, inlined from ‘int main()’ at user.cpp:83: /usr/include/bits/stdio2.h:230: warning: call to ‘__gets_warn’ declared with attribute warning: please use fgets or getline instead, gets can't specify buffer size /tmp/cc7kcC9x.o: In function `main': user.cpp:(.text+0x21e): warning: the `gets' function is dangerous and should not be used.