Main.cc: In function 'int main()': Main.cc:4:15: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings] char*str1="abc"; ^ Main.cc:5:15: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings] char*str2="abc"; ^ Main.cc:6:24: error: 'strcmp' was not declared in this scope if(strcmp(str1,str2)==0){ ^