Error during String declaration

Why does

char line[10] = "1234";

work fine but

char line[10];
line = "1234";

throws an

error: incompatible types in assign开发者_运维百科ment

error?

Arrays are not pointers. In your second example, line is a non-modifiable lvalue, but more importantly, no matter what you put on the righthand side, it can't have type char [10] (because arrays decay to pointers in non-lvalue context) and thus the types can never match.

For what it's worth, a string literal has type char [N], not const char [N] and especially not const char *, despite the fact that attempts to modify it invoke undefined behavior. (Here N is the length of the quoted text in bytes, including the added null terminator.)

The first line works because it performs an initialization of the char array with data. It would be the same as:

char line[10] = {'1', '2', '3', '4', '\0'};

In the second example, the type of "1234" is const char*, since it is a pointer to a constant char array. You're trying to assign a const char* to a char*, which is illegal. The correct way to assign a constant (or other) string to a string variable is to use strcpy, strncpy, or any other string handling function.

Because those are the rules of the language, as others have explained. I'd write it like this though and avoid declaring up-front how many characters there are.

const char* line = "1234";