Punteros en C y C++ | Conjunto 1 (Introducción, Aritmética y Array)

Los punteros almacenan direcciones de variables o una ubicación de memoria. 
 

// General syntax
datatype *var_name; 

// An example pointer "ptr" that holds
// address of an integer variable or holds
// address of a memory whose value(s) can
// be accessed as integer values through "ptr"
int *ptr;  

Usando un puntero:
 

// The output of this program can be different
// in different runs. Note that the program
// prints address of a variable and a variable
// can be assigned different address in different
// runs.
#include <stdio.h>
 
int main()
{
    int x;
 
    // Prints address of x
    printf("%p", &x);
 
    return 0;
}

// C program to demonstrate declaration of
// pointer variables.
#include <stdio.h>
int main()
{
    int x = 10;
 
    // 1) Since there is * in declaration, ptr
    // becomes a pointer variable (a variable
    // that stores address of another variable)
    // 2) Since there is int before *, ptr is
    // pointer to an integer type variable
    int *ptr;
 
    // & operator before x is used to get address
    // of x. The address of x is assigned to ptr.
    ptr = &x;
 
    return 0;
}

// C++ program to demonstrate use of * for pointers in C++
#include <iostream>
using namespace std;
 
int main()
{
    // A normal integer variable
    int Var = 10;
 
    // A pointer variable that holds address of var.
    int *ptr = &Var;
 
    // This line prints value at address stored in ptr.
    // Value stored is value of variable "var"
    cout << "Value of Var = "<< *ptr << endl;
 
    // The output of this line may be different in different
    // runs even on same machine.
    cout << "Address of Var = " <<  ptr << endl;
 
    // We can also use ptr as lvalue (Left hand
    // side of assignment)
    *ptr = 20; // Value at address is now 20
 
    // This prints 20
    cout << "After doing *ptr = 20, *ptr is "<< *ptr << endl;
 
    return 0;
}
 
// This code is contributed by
// shubhamsingh10

// C program to demonstrate use of * for pointers in C
#include <stdio.h>
 
int main()
{
    // A normal integer variable
    int Var = 10;
 
    // A pointer variable that holds address of var.
    int *ptr = &Var;
 
    // This line prints value at address stored in ptr.
    // Value stored is value of variable "var"
    printf("Value of Var = %d\n", *ptr);
 
    // The output of this line may be different in different
    // runs even on same machine.
    printf("Address of Var = %p\n", ptr);
 
    // We can also use ptr as lvalue (Left hand
    // side of assignment)
    *ptr = 20; // Value at address is now 20
 
    // This prints 20
    printf("After doing *ptr = 20, *ptr is %d\n", *ptr);
 
    return 0;
}

// C++ program to illustrate Pointer Arithmetic
// in C/C++
#include <bits/stdc++.h>
 
// Driver program
int main()
{
    // Declare an array
    int v[3] = {10, 100, 200};
 
    // Declare pointer variable
    int *ptr;
 
    // Assign the address of v[0] to ptr
    ptr = v;
 
    for (int i = 0; i < 3; i++)
    {
        printf("Value of *ptr = %d\n", *ptr);
        printf("Value of ptr = %p\n\n", ptr);
 
        // Increment pointer ptr by 1
        ptr++;
    }
}

// C++ program to illustrate Array Name as Pointers in C++
#include <bits/stdc++.h>
using namespace std;
 
void geeks()
{
    // Declare an array
    int val[3] = { 5, 10, 15};
 
    // Declare pointer variable
    int *ptr;
 
    // Assign address of val[0] to ptr.
    // We can use ptr=&val[0];(both are same)
    ptr = val ;
    cout << "Elements of the array are: ";
    cout << ptr[0] << " " << ptr[1] << " " << ptr[2];
 
    return;
}
 
// Driver program
int main()
{
    geeks();
    return 0;
}