Table of Contents
Class Pointer [C++], Data
Definition
Holds the address of another variable.
References
Data Structures Keyword Phase 2
Void Pointers
Definition
The void pointer is a generic pointer type. A pointer to void can store an address to any non-function data type, and, in C is implicitly converted to any other pointer type on assignment, but it must be explicitly cast if dereferenced inline.
References
Data Keyword 1 Phase 2 Phase 2
Dynamic Memory Allocation (Malloc/Free)
Definition
Dynamic memory allocation is the task of allocating a free chunk of memory specific to the size you predetermine in bytes, by using the malloc function. The chunk of memory is not always in the same location hence being “dynamic” instead of static. By using the “free” function, that will release the block of memory back to the system.
References
- Chapter 8: The UNIX System Interface, The C programming Language book.
- Class Notes
Demonstration (Malloc/Free)
/* * Sample code block */ #include<stdio.h> #include<stdlib.h> struct node { char value; struct node *next; }; typedef struct node Node; int main() { Node *start, *tmp, *tmp2; // Node pointers char input, i = 0; start = tmp = tmp2 = NULL; printf("Enter a value (-1 to end): "); scanf("%hhd", &input); while (input != -1) // input does not equal -1 { if (start == NULL) { tmp = tmp2 = start = (Node *) malloc(sizeof(Node)); //allocating the size of the node start->value = input; start->next = NULL; // Starts next element is null } else { tmp->next = (Node *) malloc(sizeof(Node)); tmp->next->value = input; //tmp next value= new node(user input) tmp->next->next = NULL; //tmp next next =NULL tmp = tmp->next; } printf("Enter a value (-1 to quit): "); scanf("%hhd", &input); } tmp = start; i=0; while (tmp != NULL) //tmp does not equal NULL { printf("(%hhd)%hhd -> ",i, tmp->value); // print currrent value at node tmp = tmp->next; i = i + 1; } printf("NULL\n"); printf("Enter node # to delete: "); scanf("%hhd", &input); tmp = start; if (input != 0) { for (i = 0; i < input -1; i++) tmp = tmp->next; tmp2 = tmp -> next; tmp -> next = tmp -> next -> next; tmp2 -> next = NULL; free (tmp2); } else { start = start -> next; tmp -> next = NULL; free(tmp); } tmp=start; i=0; while (tmp != NULL) //tmp does not equal NULL { printf("(%hhd)%hhd -> ",i, tmp->value); // print currrent value at node tmp = tmp->next; i = i + 1; } printf("NULL\n"); return (0); }
Alternatively (or additionally), if you want to demonstrate something on the command-line, you can do so as follows:
lab46:~$ cd src/data/Linked_List lab46:~/src/data/Linked_List$ ls lab46:~/src/data/Linked_List$ append append.c insert insertion.c link linked.c linkedlist.h node node.c remove remove.c lab46:~/src/data/Linked_List$ ./remove Enter a value (-1 to end): 1 Enter a value (-1 to quit): 2 Enter a value (-1 to quit): 3 Enter a value (-1 to quit): 4 Enter a value (-1 to quit): 5 Enter a value (-1 to quit): -1 (0)1 -> (1)2 -> (2)3 -> (3)4 -> (4)5 -> NULL Enter node # to delete: 3 (0)1 -> (1)2 -> (2)3 -> (3)5 -> NULL lab46:~/src/data/Linked_List$