Thread: double pointers

can someone please explain me the concept of double pointers refering to the following code or any other code that you think might help me clear my concept for double pointers.

Code:

struct Node
{
	int value;
	struct Node*Next;
};

case 1:
			printf("\nEnter the number to insert:\n");
			scanf("%d",&val);
			insert (&start, val);
			break;
	
			case 2:
			remove2(&start);
			break;



void insert (struct Node**start, int v)
{
	if (*start == NULL)
	{
		*start = (struct Node*) malloc(sizeof(struct Node));
		(*start)-> value = v;
		(*start)-> Next = NULL;
	}
	else{
		struct Node*temp = *start;
		while ((temp-> Next) != NULL)
		{
			temp = temp->Next;
		}
		temp->Next= (struct Node*) malloc (sizeof(struct Node));
		temp = temp-> Next;
		temp->value= v;
		temp-> Next = NULL;
	}
}


void remove2 (struct Node**start)
{
	if( *start == NULL)
	{                                   
		printf("\nThe List is Empty\n");
	}
	else
	{
		struct Node*temp= *start;
		while ((temp->Next->Next) != NULL)
		{
			temp = temp->Next;
		}
	temp->Next = NULL;
	}
}

Well, there are several possibilities when a double pointer makes sense. Suppose you pass an integer to a function and you want to modify its value, then you usually write:

Code:

void myFunc(int *myNumber)
{
    *myNumber = 10;
}

But now image that the type you want to modify is not an integer but already a pointer, then you need a pointer to that pointer:

Code:

void myFunc(int **myNumber, int *somePointer)
{
    *myNumber = somePointer;
}

Or when you have an array of strings, since a string is already of type char*, an array of strings is of type char**.