Pointer in C++

Pointer ( usage of * and & )

int a=5; //declare that a=5
int *p; // declare a pointer, p is the pointer (store the address)
p=&a // &+variable represent the address of that variable, so p equal to the address of the variable

printf("the value of a %d\n",*p) // *p will first use the address store in the p, to find the value. *p ---> (p store the address of a) ---> find the value in that address ---> 5

• p is pointer, storing the address of a
• *p can return the corresponding value of that address —> a=5
• p=&a assign the address of a to the pointer p, so p contain address of a
• int *p declare the pointer

& meaning the memory address of the operator / variables, if a function take a parameter as a pointer and i passing the &a to the function, it means pass by reference. it will affect the variable even outside the function.

#include <stdio.h>

int add (int *p){
	*p=10;
}

int main(){

	int a=5;
	printf("The value of a %d\n",a);
	add(&a);
	printf("The value of a %d\n",a);
	return 0;
}

Usage of void *

void * is generic pointer that can be used to represent the pointer in any data type –> untyped.

int a=5;
char b='d';


// usage 1, Pointer to any type

void *pr; // declare a pointer with untyped

pr=&a; // pr store the address of a
pr=&b;

// usage 2 Casting
void *pr=&a;
int *c=(int *)pr // convert the untyped pointer to int pointer type and then assign to new integer pointer 
// (int *) emphasize that it should convert to int pointer type. 

tech — Feb 22, 2024