Compilare: user.cpp: In function ‘void pref(int)’: user.cpp:37: warning: comparison between signed and unsigned integer expressions user.cpp:44: warning: unused variable ‘ok’ user.cpp: In function ‘int main()’: user.cpp:65: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:69: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:72: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:75: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp: In function ‘int key(int, char*)’: user.cpp:17: warning: ‘key’ may be used uninitialized in this function