DEV Community

Cover image for Pointers : what are they pointing to?
Gurchetan
Gurchetan

Posted on • Updated on

Pointers : what are they pointing to?

Pointers in C

Pointers are a fundamental concept in C programming that enable you to directly access and manipulate memory. Understanding pointers is crucial for effective and efficient C programming.

What is a Pointer?

A pointer is a value that represents a memory address. It points to a specific memory location, allowing you to access and modify the value stored at that location.

Basic Example

int some_var = 4;
int *pointer_to_some_var = &some_var;
Enter fullscreen mode Exit fullscreen mode

here &some_var is address of some_var;

Symbol Function Example
some_variable Holds the value in certain memory location int x = 3;
* Points to memory address of a certain variable int *pX;
& Holds the value of address of following variable &x;

Image description

references and De-referencing

Symbols what it holds/means Example code
Declared variable Value of the variable `int x = 10;`
A pointer pointer points to some address int *p = &x;
Address of the variable(&) Memory location of variable(eg:0x7ffe2f14f97c ) printf("Address of variable x is %p",(void*)&x);
Pointers name itself with a preceding &(pointer variable) Memory address of pointer (eg:0x7ffe2f14f97c) printf("Address of pointer p is %p",(void*)&p);
pointer preceded by * (not to be confused with initialization of a pointer type) Value pointed to by pointer(also called dereferencing) printf("Value pointed by pointer p is %d",*p);

Why use Pointers?

Pointers help manage scope issues, especially when using functions with structures. By using pointers, you can access out-of-scope variables in functions through their memory addresses.

We use pointers to access out of scope variables in functions by providing pointer pointing to memory address of such variable (or structure).

Example

#include <stdio.h>
#include <stdbool.h>

struct employee_type
{
    int id;
    int income;
    bool staff;
};

void initialize_employee(struct employee_type *e){
    e->id = 0;
    e->income=0;
    e->staff=true;

    return;
}
int main(){
    struct employee_type Ralph;    
    initialize_employee(&Ralph);

    printf("%d", Ralph.income);
}
Enter fullscreen mode Exit fullscreen mode

Common Pitfalls

  • Uninitialized Pointers: Always initialize pointers. An uninitialized pointer points to a random memory location, leading to undefined behavior.

  • Dangling Pointers: Do not use pointers to memory that has been freed or gone out of scope.

  • Pointer Arithmetic: Be careful with pointer arithmetic to avoid accessing memory out of bounds.

Top comments (0)