Why can't I edit a char in a char*?

Question

Below is an exceedingly simple example. It compiles fine using gcc on Mac OS X (Snow Leopard). At runtime it outputs Bus error: 10. What\'s happening here?

Answer 1

This

char* a = "abc";

relies on a dangerous implicit conversion from const char[] (the type of a string literal) to char*. (In C++ this conversion has been deprecated for more than a decade. I don't know about C, though.)

A string literal must not be altered.