DPTR is a 16-bit register
DPTR is made up of two 8-bit registers: DPH and DPL
DPTR holds the memory addresses for internal and external code access and external data access
(eg. MOVC A,@A+DPTR MOVX A,@DPTR MOVX @DPTR,A )
DPTR is under the control of program instructions and can be specified by its 16-bit name, or by each individual byte name, DPH and DPL DPTR does not have a single internal address; DPH and DPL are each assigned an address
A pointer is an address or the name for the location for an item of data. An uninitialised pointer is one that has not been assigned an initial value or item of data.
Microprocessor has 16 address lines and microcontroller has 20 address lines
A Null pointer has the value 0. void pointer is a generic pointer introduced by ANSI. Before ANSI, char pointers are used as generic pointer. Generic pointer can hold the address of any data type. Pointers point to a memory address, and data can be stored at that address.
yarrak yaparsın.
Generic pointer of type 'void *' is compatible with any (data-)pointer, but you cannot use the following operators on it: + - ++ -- += -= * -> []
Storing address of data.
It depends on what type of data you wish to manipulate.
When we increment the pointer its value is increased by the length of the data type that it points to.
pointer data type that carry address:of data type that has no name but both of them must have same data type. structures you can make your own data type: struct name put any data type you wants any functions.
#include<stdio.h> #include<stdlib.h> typedef struct Node { int data; struct Node *next; }node; void insert(node *pointer, int data) { /* Iterate through the list till we encounter the last node.*/ while(pointer->next!=NULL) { pointer = pointer -> next; } /* Allocate memory for the new node and put data in it.*/ pointer->next = (node *)malloc(sizeof(node)); pointer = pointer->next; pointer->data = data; pointer->next = NULL; } int find(node *pointer, int key) { pointer = pointer -> next; //First node is dummy node. /* Iterate through the entire linked list and search for the key. */ while(pointer!=NULL) { if(pointer->data == key) //key is found. { return 1; } pointer = pointer -> next;//Search in the next node. } /*Key is not found */ return 0; } void delete(node *pointer, int data) { /* Go to the node for which the node next to it has to be deleted */ while(pointer->next!=NULL && (pointer->next)->data != data) { pointer = pointer -> next; } if(pointer->next==NULL) { printf("Element %d is not present in the list\n",data); return; } /* Now pointer points to a node and the node next to it has to be removed */ node *temp; temp = pointer -> next; /*temp points to the node which has to be removed*/ pointer->next = temp->next; /*We removed the node which is next to the pointer (which is also temp) */ free(temp); /* Beacuse we deleted the node, we no longer require the memory used for it . free() will deallocate the memory. */ return; } void print(node *pointer) { if(pointer==NULL) { return; } printf("%d ",pointer->data); print(pointer->next); } int main() { /* start always points to the first node of the linked list. temp is used to point to the last node of the linked list.*/ node *start,*temp; start = (node *)malloc(sizeof(node)); temp = start; temp -> next = NULL; /* Here in this code, we take the first node as a dummy node. The first node does not contain data, but it used because to avoid handling special cases in insert and delete functions. */ printf("1. Insert\n"); printf("2. Delete\n"); printf("3. Print\n"); printf("4. Find\n"); while(1) { int query; scanf("%d",&query); if(query==1) { int data; scanf("%d",&data); insert(start,data); } else if(query==2) { int data; scanf("%d",&data); delete(start,data); } else if(query==3) { printf("The list is "); print(start->next); printf("\n"); } else if(query==4) { int data; scanf("%d",&data); int status = find(start,data); if(status) { printf("Element Found\n"); } else { printf("Element Not Found\n"); } } } }
Because its a microcontroller with an 8 bit data bus width.
On 8-bit processors it is 16 bit, but in some processors (MosTek 65xx) the upper eight bit is constant 00000001.