pointers to pointers in cpp

1#include <iostream>
2 
3using namespace std;
4 
5int main () {
6   int  var;
7   int  *ptr;
8   int  **pptr;
9
10   var = 3000;
11
12   // take the address of var
13   ptr = &var;
14
15   // take the address of ptr using address of operator &
16   pptr = &ptr;
17
18   // take the value using pptr
19   cout << "Value of var :" << var << endl;
20   cout << "Value available at *ptr :" << *ptr << endl;
21   cout << "Value available at **pptr :" << **pptr << endl;
22
23   return 0;
24}

1#include <iostream>
2using std::cout;
3
4int main() {
5  /* 
6  Some things to keep in mind:
7  	-you shouldn't circumvent the type system if you are creating raw ptrs
8  	and don't need to "type pun" or cast (don't use void ptrs)
9    -ptr types only reference memory (which are integers), not actual data, thus
10    they should not be treated as data types
11    char* is just 1 byte of mem, int* is just 4 bytes of mem, etc
12    - '*' means that you are creating a pointer which "points" to the mem address
13    of a variable
14    - '&', in this case, means "get the mem address of this variable"
15  */
16  
17  void* ptr; // a pointer that doesn't reference a certain size of memory
18  int* int_ptr; // a pointer that points to data with
19  				// only 4 bytes of memory (on stack)
20  
21  int a = 5; // allocates 4 bytes of mem and stores "5" there (as a primitive)
22  ptr = &a; // can only access the memory address of 'a' (not the data there)
23  
24  int b = 45; 
25  int_ptr = &b; // can access both memory address and data of 'b'
26  
27  cout << ptr << "\n"; // prints mem address of 'a'
28  /*cout << *ptr << "\n"; <- this will error out; a void ptr cannot be 
29  							 derefrenced */
30  cout << *(int*)ptr << "\n"; // type punning to get around void ptr (extra work)
31  
32  cout << int_ptr << "\n"; // mem address of b
33  cout << *int_ptr << "\n"; // data stored at b
34  
35  /* -- OUTPUTS -- */
36  /*
37  	some memory address (arbitrary) which contains 05 00 00 00 as its data
38  	5
39    some memory address (arbitrary) which contains 2D 00 00 00 as its data
40    45
41  */
42  
43  return 0; // you only need this if "main" isnt the linker entry point
44  			// you also don't care
45  
46  // ur also probably wondering why I didn't using namespace std... cherno
47}