Assigning strings to arrays of characters

Question

I am a little surprised by the following.

Example 1:

char s[100] = \"abcd\"; // declare and initialize - WORKS

Example 2:

Answer 1

Initialization and assignment are two distinct operations that happen to use the same operator ("=") here.

Answer 2

When initializing an array, C allows you to fill it with values. So

char s[100] = "abcd";

is basically the same as

int s[3] = { 1, 2, 3 };

but it doesn't allow you to do the assignment since s is an array and not a free pointer. The meaning of

s = "abcd" 

is to assign the pointer value of abcd to s but you can't change s since then nothing will be pointing to the array.
This can and does work if s is a char* - a pointer that can point to anything.

If you want to copy the string simple use strcpy.

Answer 3

I know that this has already been answered, but I wanted to share an answer that I gave to someone who asked a very similar question on a C/C++ Facebook group.

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Arrays don't have assignment operator functions*. This means that you cannot simply assign a char array to a string literal. Why? Because the array itself doesn't have any assignment operator. (*It's a const pointer which can't be changed.)

arrays are simply an area of contiguous allocated memory and the name of the array is actually a pointer to the first element of the array. (Quote from https://www.quora.com/Can-we-copy-an-array-using-an-assignment-operator)

To copy a string literal (such as "Hello world" or "abcd") to your char array, you must manually copy all char elements of the string literal onto the array.

char s[100]; This will initialize an empty array of length 100.

Now to copy your string literal onto this array, use strcpy

strcpy(s, "abcd"); This will copy the contents from the string literal "abcd" and copy it to the s[100] array.

Here's a great example of what it's doing:

int i = 0; //start at 0
do {
    s[i] = ("Hello World")[i]; //assign s[i] to the string literal index i
} while(s[i++]); //continue the loop until the last char is null

You should obviously use strcpy instead of this custom string literal copier, but it's a good example that explains how strcpy fundamentally works.

Hope this helps!