In C, why can't I assign a string to a char array after it's declared?

Arrays are second-class citizens in C, they do not support assignment.

char x[] = "This is initialization, not assignment, thus ok.";

This does not work:

x = "Compilation-error here, tried to assign to an array.";

Use library-functions or manually copy every element for itself:

#include <string.h>
strcpy(x, "The library-solution to string-assignment.");

me.name = "nikol"; is wrong !! you need to use strcpy()

when you do x = "Some String", actually you are putting the starting address of the static string "Some String" into variable x. In your case, name is a static array, and you cannot change the address. What you need, is to copy your string to the already allocated array name. For that, use strcpy().

First of all, you need to know the following points:

• In C, text strings are just arrays.
• In C, array variables are basically just pointers.

So, char mytext[12]; is essentially just declaring a char pointer called mytext that stores the address of the first (zero'th) element of the array/string.

This code is therefore valid:

#include <stdio.h>
int main(int argc, char *argv[])
{
    const char a[] = "Hello";
    const char *b = a;
    printf("%s\n", b);
    return 0;
}

The important thing to note here is that re-assigning b doesn't change the contents of whatever it points to - it changes the thing that it points to.

However, there are cases where arrays and pointers behave differently. In the example above, a cannot be reassigned. If you try, you'll get an error.

To go back to you original example, this structure:

struct person{
    char name[15];
    int age;
};

...can be thought of as a 19-byte structure* of which the first 15 bytes are earmarked for storing a string. The name attribute stores the address of the first byte, so you know where those 15 bytes live in memory - you just need to write something useful into them.

This is where functions such as sprintf() or strcpy() come into play - they copy data into the address defined by name rather than re-assigning name itself.

* Assuming that sizeof(int) is 4 and the structure is not padded, of course...