No, If you quote a string in c "string data here" you get a piece of data with null termination.

Null termination is part of the C language.

Example: char str[]= "1234";

    printf ("%s: %lu", str, sizeof(str));

Prints: 1234: 5

Use "%zu" to print a value of type size_t.

A couple of ugly corner cases:

    const char str[] = "abcd\0efgh";
    printf("length = %zu, size = %zu, value = \"%s\"\n",
           strlen(str), sizeof str, str);

output:

    length = 4, size = 10, value = "abcd"

And:

    const char str[4] = "abcd";
    printf("length = %zu, size = %zu, value = \"%s\"\n",
           strlen(str), sizeof str, str);

This has undefined behavior. (Which is a good reason to let the compiler figure out how big the array has to be. Computers are better at counting things than you are. Let them.)

> Should the C language represent strings as an address + length tuple or just as the address with a magic character (NUL) marking the end?

This explicitly is a different kind of representation in memory.