Compilare: user.cpp: In function ‘int main()’: user.cpp:59:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < D.size() && ok; i++) ~~^~~~~~~~~~ user.cpp:61:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < M.size() && ok; i++) ~~^~~~~~~~~~ user.cpp: In function ‘char nextch()’: user.cpp:10:36: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buf, 1, BUF_SIZE, fi); ^