Compilare: user.cpp: In function ‘void read()’: user.cpp:17: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:19: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp: In function ‘void df(int)’: user.cpp:31: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void write()’: user.cpp:49: warning: comparison between signed and unsigned integer expressions