Understanding char** in C/C++

In C and C++, char** is a pointer to a pointer of type char. It is commonly used to represent arrays of strings, such as command-line arguments (argv), dynamic arrays of strings, or 2D arrays where each row is a string. Though initially confusing, with some examples, you’ll see how it operates similarly to handling a "table of strings."

What is char* *?
A char* is a pointer to a char, representing a single string.
A char** is a pointer to a char*, which means it points to an array of strings (or an array of char* pointers).

Example:

#include <stdio.h>

int main() {
    char* strings[] = {"I love", "Embedded", "Systems"};

    // Create a char** pointer to the strings array
    char** string_ptr = strings;

    // Access and print the strings using char**
    for (int i = 0; i < 3; i++) {
        printf("%s\n", string_ptr[i]);
    }

    return 0;
}

Breakdown:

• char* strings[]: Declares an array named strings, with each element pointing to a character (a char*), essentially forming an array of strings.
• {"I love", "Embedded", "Systems"}: Initializes the strings array with string literals stored in memory as character arrays. The compiler converts these literals into char* pointers, assigned to the array elements.

Visual Representation:

Main Index (char**) → String 1 (char*) → "I love"
                   → String 2 (char*) → "Embedded"
                   → String 3 (char*) → "Systems"

Key Points:

• strings is an array of pointers to strings, not an array of characters.
• Each element of the array points to the first character of a string literal.
• You can manipulate individual characters within the strings using pointer arithmetic or array indexing.

Conclusion:

• char** is a pointer to an array of strings, much like a "table of strings."
• Memory is allocated separately for each string (row), allowing you to work with each string individually.
• Functions can modify the contents of the strings because char** passes a reference to the original array of pointers.

Working with char** is powerful when handling dynamic arrays, command-line arguments, or multi-dimensional arrays of strings in C/C++. Once you understand its structure, it simplifies the process of managing arrays of strings in your programs.