Dereferencing pointer in C

Introduction:

In C, dereferencing a pointer refers to gaining access to the value kept at the memory address the pointer holds. Pointers contain variables that have the values of memory addresses. Dereference is a pointer to get the data when you wish to access the actual data kept at a specific memory address.

The asterisk (*) operator is used to accomplish the dereferencing process. The grammar for dereferencing the pointer is as follows:

*pointer_variable;

Process of dereferencing:

A detailed description of the process of dereferencing is provided below:

• Create a pointer variable: To begin, create a pointer variable with a particular data type. As an illustration, you would define a reference to an integer as follows:

Int *ptr; // ptr is a pointer to an integer

• Give the pointer a memory address: A pointer must point to a legitimate memory location before it is possible to dereference it. Either directly assigning it to the address of a variable that already exists or dynamically allocating memory with techniques like malloc() are both acceptable ways to accomplish this:

int num = 42;

ptr = # // ptr now holds the memory address of the 'num' variable

• Dereference the pointer: A dereference operator (*) can access the value at a valid memory address where the pointer is pointing.

Int value = *ptr; // 'value' will now hold the value of 'num', which is 42

Example:

#include <stdio.h>

int main() {

    int num = 42;

    int *ptr = &num; // ptr holds the memory address of num

    printf("Value of num: %d\n", num);

    printf("Value of ptr: %p\n", (void *)ptr); // %p is used to print memory addresses

    // Dereferencing the pointer to access the value it points to

    printf("Value pointed by ptr: %d\n", *ptr);

    return 0;

}

Explanation:

• An integer variable named num is created, and its value is 42.
• With the & (address-of) operator, we create an integer pointers ptr and initialize it with the num's memory address.
• We display the values of num and ptr on paper. We utilize the%p format specifier to output memory locations when printing ptr. We cast ptr to (void *) to comply with the format specifier requirements.
• The result is reported as "Value pointed by ptr" when we use the * operator to dereference the pointer ptr.

Output:

Explanation:

• The value of the number parameter is shown as 42 in the text "Value of num: 42".
• The memory location where the variable num is kept is shown on "Value of ptr: 0x7ffc62e33854". Every time you execute the program, the precise memory address could change.
• Dereferencing a pointer to ptr yields a path "Value pointed by ptr: 42". It displays a num value stored at the storage address that ptr is pointing to.

Importance of dereferencing pointer in C:

• Pointers offer a means of indirectly gaining access to data stored in memory. You can read or change a value contained at the address in memory that a pointer points to by dereferencing the reference. It is notably helpful for effectively transmitting data between functions or interacting with dynamically allocated memory.
• Utilizing methods like malloc(), calloc(), or realloc(), you may allocate memory dynamically in C. These operations provide pointers to the memory space reserved. You must dereference these pointers to access or modify the information in the randomly allocated memory.
• Accessing complicated Data Structures Efficiently: Pointers, rather than dealing directly with the data, might be more effective when working with complicated data structures like arrays of values, linked lists, trees, or structs. You can access and edit the components of these data structures by dereferencing pointers.
• Pointers are frequently used to send parameters for functions or retrieve values from functions, respectively. Passing "out" parameters in C is feasible because functions can directly affect the information stored at the memory addresses supplied as arguments by dereferencing pointers.
• Implementing Data Structures and Algorithms: Many algorithms and data structures rely on pointers to manage memory and create connections between data components. For appropriate communication with these frameworks and algorithms, dereferencing is required.
• Dynamic Data Sharing: Pointers allow data to be shared across various program components. Several processes or modules can access and alter the same data using the exact memory location (pointer), allowing for effective coordination and communication.
• Memory management and resource use: Effective memory management and resource use in C programs depend on properly dereferencing and disposal of dynamically allocated memory.
• Pointers are frequently used to get access to memory-mapped I/O, drivers for devices, and additional system resources when interfacing with an operating system or low-level hardware.

Purpose of dereferencing pointer in C:

• Accessing Data in Dynamic Memory Allocation: Functions like malloc(), calloc(), and realloc() return a reference to the allocated memory when used to allocate memory dynamically. It would help if you dereferenced the pointer to interact with the data in that dynamically created memory.
• Pointers are frequently used to send parameters to functions. It is known as pointer modification. You can create "out" parameters by directly altering the original data supplied as arguments by dereferencing pointer variables inside of a function.
• Pointers are widely utilized in the implementation of data structures, including arrays, linked lists, trees, and graphs, which allow for efficient access to data. You can efficiently access and edit items by dereferencing pointers.
• Data Sharing across Functions or Modules: Pointers allow data to be shared across other program components. Several processes or modules can modify the same data using the exact memory location (pointer), streamlining communication and cooperation.
• Functions in C may only directly return one value; multiple values cannot be returned from a single function. However, you may return several values from a function using the pointers, which can be altered within the function by utilizing pointers as function arguments.
• Interfacing with the computer's operating system and low-level hardware: Pointers are frequently employed when communicating with the operational system or low-level hardware. They make it possible to communicate with storage-mapped I/O, device drivers, and additional system resources and directly access memory.