Character Pointer Variables

A char* is a pointer type that holds the address of a character. It can point to a single character or the first element of a null-terminated string.

For example:

int main() {
    char ch = 'w';
    char *ptr_to_ch = &ch;
    *ptr_to_ch = 'w'; // modifies ch via pointer
    return 0;
}

Another common usage involves string literals:

int main() {
    const char *msg_ptr = "hello bit.";
    printf("%s\n", msg_ptr);
    return 0;
}

Here, msg_ptr does not store the entire string. Instead, it stores the memory address of the first character 'h'. The string literal "hello bit." resides in a read-only section of memory (typically .rodata), and msg_ptr points to its starting location.

A classic comparison illustrates this behavior:

#include <stdio.h>

int main() {
    char arr1[] = "hello bit.";
    char arr2[] = "hello bit.";
    const char *lit1 = "hello bit.";
    const char *lit2 = "hello bit.";

    if (arr1 == arr2)
        printf("arr1 and arr2 are same\n");
    else
        printf("arr1 and arr2 are not same\n");

    if (lit1 == lit2)
        printf("lit1 and lit2 are same\n");
    else
        printf("lit1 and lit2 are not same\n");

    return 0;
}

This outputs:

arr1 and arr2 are not same
lit1 and lit2 are same

Explanation: arr1 and arr2 are distinct arrays allocated on the stack — each gets its own copy of the string. In contrast, lit1 and lit2 both point to the same string literal stored once in read-only memory, so their addresses compare equal.

Array Pointer Variables

An array pointer is a pointer that points to a entire array—not to individual elements, but to the array object itself.

Contrast with pointer arrays, which are arrays whose elements are pointers:

int *ptr_array[5]; // array of 5 int pointers

Where as an array pointer is declared as:

int (*arr_ptr)[5]; // pointer to an array of 5 ints

The parentheses around *arr_ptr are essential: they indicate that arr_ptr is a pointer, and the [5] specifies it points to an array of five integers.

Example usage:

int main() {
    int data[5] = {10, 20, 30, 40, 50};
    int (*p)[5] = &data; // p points to the whole array

    printf("Address of data: %p\n", (void*)data);
    printf("Address held by p: %p\n", (void*)*p);
    printf("First element via p: %d\n", (*p)[0]); // equivalent to data[0]

    return 0;
}