CPP

pointers in c++

/*
Here is how pointers work in a nustshell(represent | as what's
happening in the memory and / as a place in the ram):
int x = 2; | 2/0x00ef5
int *z = &x| 0x00ef5/0x00ef6 (See how the value of the pointer z
matches with the memory address of x? that's how they work!)

when you print out the pointer as *n (replace n with the var name)
it will actually look at the value
see it's a memory address
go to that memory address
and print the value originally in the memory address which is 2

Here is code:
*/
int x = 5;
int *y = &x;
cout << *y+1;
/*
the reason why i did *y+1 was so to show that after it got
the value from the memory address it will add 1
*/

pointers in c++

#include <iostream>

using namespace std;

int main()
{
   int x=5;
   int *ptr=&x;
   cout<<&x<<endl;        //prints the address of the variable (x)
   cout<<ptr<<endl;       //prints the address of the variable (x)
   cout<<*ptr<<endl;      //prints the value of x(5)
   cout<<&ptr<<endl;      //prints the address of the pointer (ptr)
   
   
}

pointer cpp

type *ptr;   // Declare a pointer variable called ptr as a pointer of type
// or
type* ptr;
// or
type * ptr;  // I shall adopt this convention

c++ pointers and functions

#include <iostream>

using namespace std;

void increment(int *n){  		//declare argument of the functon as pointer
    *n+=1;
   cout<<"In function: "<<*n<<endl; 
}

int main()
{
   int x=5;			
   increment(&x);		//passing the address of the variable to the function
   cout<<"In main: "<<x<<endl;
   
}

pointer c++

int myvar = 6;
int pointer = &myvar; // adress of myvar
int value = *pointer; // the value the pointer points to: 6

why do we use pointers in c++

//why do we use pointers:
1)pass values by refrence to a function
2)return multiple values from a function
3)use pointers in combinational with arrays
4)dynamic memory allocation
5)use pointers in a base class in order to access object of derived class (Smart pointers)

C++ pointer

#include <iostream>

int main() 
{

	int* ptr = new int{};
    // creates null initialized pointer ptr
    
    delete ptr; // must be cleared manually
    

	// multiple memaddress allocation:

	int* p_arr = new int[5]{};
    /*
    new int[] returns the first elems pointer address
    {} initializes with default settings [int{} -> 0], such as MyObj()
    
    [5] -> can be var too, new functionality in modern cpp (new int[var_count])
    */
    
    delete[] p_arr;
}

c++ fonksion pointer

#include <stdio.h>
int f1(int x) { return x * 2; }
int f2(int x) { return x * 4; }

int main()
{
    int (*fptr1)(int) = &f1;
    fptr1 = &f2;
  	fptr1(3);
}

Pointers in c++

int x = 2;
int *y = &x;

cout << *y;

pointer in c++

// Variable is used to store value
int a = 5;
cout << a; //output is 5

// Pointer is used to store address of variable
int a = 5;
int *ab;
ab = &a; //& is used get address of the variable
cout << ab; // Output is address of variable

c++ pointer

int *ptr;
int arr[5];

// store the address of the first
// element of arr in ptr
ptr = arr;

///////// same as above

int *ptr;
int arr[5];
ptr = &arr[0];

C/C++ Pointers

int* pc, c;
c = 5;
pc = &c;
printf("%d", *pc);   // Output: 5

pointers c++

baz = *foo;

c++ function pointer

// Here's a macro I use to define a type.
// You're welcome to use it, but I'll also show how the type is defined.
#define d_typedef_func_ty(return_z, name, ...) typedef return_z (*name)(__VA_ARGS__);
d_typedef_func_ty(int, int_2i_f, int, int); // creates a int(*)(int, int) function pointer
// which is equivelant to the following:
typedef int(*int_2i_f)(int, int);

C++ Pointers to Structure

#include <iostream>
using namespace std;

struct temp {
    int i;
    float f;
};

int main() {
    temp *ptr;
    return 0;
}

C++ Pointers

string food = "Pizza"; // A food variable of type string

cout << food;  // Outputs the value of food (Pizza)
cout << &food; // Outputs the memory address of food (0x6dfed4)

pointer to pointer c++

#include <iostream>
using namespace std;

struct Distance {
    int feet;
    float inch;
};

int main() {
    Distance *ptr, d;

    ptr = &d;
    
    cout << "Enter feet: ";
    cin >> (*ptr).feet;
    cout << "Enter inch: ";
    cin >> (*ptr).inch;
 
    cout << "Displaying information." << endl;
    cout << "Distance = " << (*ptr).feet << " feet " << (*ptr).inch << " inches";

    return 0;
}

C/C++ Pointers

int* pc, c;
c = 5;
pc = &c;
c = 1;
printf("%d", c);    // Output: 1
printf("%d", *pc);  // Ouptut: 1

pointer in cpp details

#include <iostream>
using namespace std;
class Demo {
private:
  int num;
  char ch;
public:
  void setMyValues(int num, char ch){
    this->num =num;
    this->ch=ch;
  }
  void displayMyValues(){
    cout<<num<<endl;
    cout<<ch;
  }
};
int main(){
  Demo obj;
  obj.setMyValues(100, 'A');
  obj.displayMyValues();
  return 0;
}

C/C++ Pointers

#include <stdio.h>
int main()
{
  int var = 5;
  printf("var: %d
", var);

  // Notice the use of & before var
  printf("address of var: %p", &var);  
  return 0;
}

C/C++ Pointers

int* p;

C/C++ Pointers

int *p1;
int * p2;

C/C++ Pointers

int* pc, c;
c = 5;
pc = &c;
c = 1;
printf("%d", c);    // Output: 1
printf("%d", *pc);  // Ouptut: 1

C++ Pointers to Structure

#include <iostream>
using namespace std;
struct Distance {
    int feet;
    float inch;
};
int main() {
    Distance *ptr, d;
    ptr = &d;
        cout << "Enter feet: ";
    cin >> (*ptr).feet;
    cout << "Enter inch: ";
    cin >> (*ptr).inch;
     cout << "Displaying information." << endl;
    cout << "Distance = " << (*ptr).feet << " feet " << (*ptr).inch << " inches";
    return 0;
}

pointers in cpp

int *ip; // pointer to an integer
double *dp; // pointer to a double
float *fp; // pointer to a float
char *ch // pointer to character

pointer in c++

uIndex = uchCRCLo ^ *puchMsg++ ; // pointer used in varible incriment

Pointers c++

// This will explain how pointers are used
#include <iostream> 
using namespace std; 
int main() 
{     
  int a = 5;  //Declare and initialize a variable
  /*
  The following pointer declarations are all valid and they all are doing the same:
  Declaring a new pointer and initializing it with 0 (a non accessible memory address) for safety-reasons.
  int * b = 0;
  int* b = 0                 
  int *b = 0; // This is how its usually written.
  int *b; // <= this, however would cause "b" to point to some random address which might be unsafe.
  */
  int *b = 0; // Create a new pointer of type int and initialize it with 0

  cout << ""b" is initialized and now pointing to memory-address:  " << b << endl << endl;

  //Now make the pointer "point" to the address of a
  b = &a; //"b" now points to the address of "a"

  cout << ""a" is stored at memory-address:  " << &a << endl;
  cout << ""b" is stored at memory-address:  " << &b << endl;
  cout << ""b" is pointing to memory-address now:  " << b << endl << endl;

  cout << "The value of "a" is: " << a << endl;  // returns the value of a

  //the "*b" will get the value from the address b points to (the value of a)
  cout << "The value of the area "b" is pointing to is: " << *b << endl << endl << endl;

  //Now modify the value of the address "b" is pointing to...effectively changing the value of "a"     
  *b=10;

  cout << ""a" is still stored at memory-address:  " << &a << endl;
  cout << ""b" is still stored at memory-address:  " << &b << endl;
  cout << ""b" is still pointing to memory-address:  " << b << endl << endl;

  cout << "The value of "a" is now: " << a << endl;  // returns the value of a
  cout << "The value of the area "b" is pointing to is now: " << *b << endl << endl;

  return 0;        
}

pointers in c++

void simple_pointer_examples() {
    int   a;  // a can contain an integer
	int*  x;  // x can contain the memory address of an integer. 
 	char* y;  // y can contain the memory address of a char. 
 	Foo*  z;  // z can contain the memory address of a Foo object.  
 
    a = 10;
    x = &a;   // '&a' extracts address of a 
  
    std::cout <<  x << std::endl; // memory address of a => 0x7ffe9e25bffc
    std::cout << *x << std::endl; //          value of a => 10
}