Why array assignment operation doesn't exist but structure assignment does in C language?

Question

int a[10];
int b[10];

a = b; // illegal

typedef struct {
    int real;
    int imag;
    } complex;

complex c,d;
c = d; //legal

[I realize that

Answer 1

The main reason is of course the Standard. On the assignment operator constraint it says:

(C99, 6.5.16p2) "An assignment operator shall have a modifiable lvalue as its left operand"

where it defines a modifiable lvalue as

(C99, 6.3.2.1p1) "A modifiable lvalue is an lvalue that does not have array type, [...]".

So assigning to arrays is not permitted.

But the main reasons are historical reasons at the times where array copy was considered not appropriate for the hardware (the old PDP systems). Not that also in the first versions of C, the assignment of structure types objects was also not allowed. It was later added to the language but for the array to many parts of the language would have been needed to be changed to allow to assign to arrays.