Compilare: user.cpp: In function ‘void pref(int)’: user.cpp:29: warning: comparison between signed and unsigned integer expressions user.cpp:34: warning: unused variable ‘ok’ user.cpp: In function ‘int main()’: user.cpp:53: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:57: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:60: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:63: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp: In function ‘void pref(int)’: user.cpp:21: warning: ‘c1’ may be used uninitialized in this function