Compilare: user.cpp: In function ‘int main()’: user.cpp:11:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<strlen(s);i++) ~^~~~~~~~~~ user.cpp:13:22: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if(s[i]>='a' && s[i]<='z' or s[i]>='A' && s[i]<='Z') ~~~~~~~~~~^~~~~~~~~~~~