C style strings, Pointers, arrays

Question

I\'m having trouble understanding what a C-style string is. Happy early New Year

What I know: A pointer holds a memory address. Dereferencing the pointer will give you

Answer 1

You are asking two questions here, one of which is more general and which I will answer first.

A pointer is a 'handle' (called an address) to a location in memory. The contents of that location is a value. How that value is interpreted is dependent on the 'type' of the pointer. Think of it this way: an address is the location of a house, for example, 10 Main Street. The contents of 10 Main Street are the contents of the house at that address. In C (and C++) terms:

int *p;

Is a variable that can hold the address of an integer.

int x;

Is a variable that IS an integer.

p = &x;

Has p 'point to' x by storing in p the ADDRESS of x.

x = 10;

Stores in x the value 10.

*p == x

Because *p says to 'use the contents of p' as a value and then compare it to x.

p == &x

Because &x says to 'use the address of x' as a value and then compare it to p, which is a variable of type pointer.

A string, which is a sequence of zero or more characters is represented in C (and C++) by the characters " and ". In memory, these values are stored consecutively and are automatically terminated by a trailing null byte, which is a byte with the value 0. The string "Hello, world!" is stored in memory, assuming you are using an 8 bit ASCII character encoding, as:

65 101 108 108 111 44 32 87 111 114 108 33 0

You can see this for yourself using the following code snippet:

char *p = "Hello, World!";
int len = strlen(p);
int i;

for (i = 0; i <= len;  ++i)
{
    std::cout << std::dec << (int) p[i] << ' ';
}
std::cout << std::endl;

Since the null (zero byte) is automatically added to a constant string by the compiler, the following two arrays are the same size:

char a1[7] = { 'H', 'i', ' ', 'y', 'o', 'u', '\0' };
char a2[] = "Hi you";

std::cout << strcmp(a1, a2) << std::endl

Simply put, a 'C style string' is simply an array of characters terminated by a null, which answers your first question.