You're confusing things a little bit. 'char s[] = "foo"' is equivalent to 'char s[] = { 'f', 'o', 'o', '\0' }' and gives you a normal mutable array (or you can make it const and then it's const; no surprises); it is okay to mutate that array. 'char * s = "foo"' gives you a pointer to a string literal that might be placed in read-only storage; in C++ it is a const char * (so modern compilers should complain about that initialisation), while in C it is a char * where it's UB if you modify it (compilers may warn about storing it in a non-const char *; many don't).