Compilare: user.cpp: In function ‘int main()’: user.cpp:21:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<strlen(sir);i++) ^ user.cpp:24:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<strlen(sir);i++) ^ user.cpp:29:57: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(sir[i]<='9' && sir[i]>='0' && i<strlen(sir)) ^ user.cpp:41:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<strlen(sir) ) ^ user.cpp:48:57: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(sir[i]<='9' && sir[i]>='0' && i<strlen(sir)) ^ user.cpp:59:9: warning: statement has no effect [-Wunused-value] { OK==1; ^