a double linked list loop

please help me identifying the problem in the following program's do while loop.

Code:

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#include<stdio.h> //implemening double linked list
typedef struct _auistud{
        char name[20];
        int gpa,id;
        struct _auistud *next;
        struct _auistud *previous;
}auistud;
int
main(void){
        auistud *_new,*rear,*head;
        char ans;
        _new=(auistud*)malloc(sizeof(auistud));
        printf("please enter the name\n");
        scanf("%s",_new->name);
        printf("please enter the id\n");
        scanf("%d",&_new->id);
        printf("please enter the gpa\n");
        scanf("%d",&_new->gpa);
        head=_new;
        rear=head;
        do{
                _new=(auistud*)malloc(sizeof(auistud));
                        printf("please enter the name\n");
                scanf("%s",_new->name);
                printf("please enter the id\n");
                scanf("%d",&_new->id);
                printf("please enter the gpa\n");
                scanf("%d",&_new->gpa);
                rear->next=_new;
                _new->previous=rear;       
                printf("please enter yes or no\n");
                scanf("%c",&ans);
        }while(ans=='y');
        rear->next=NULL;
return(0);
}

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Code:

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do{
    _new=(auistud*)malloc(sizeof(auistud));
    printf("please enter the name\n");
    scanf("%s",_new->name);
    printf("please enter the id\n");
    scanf("%d",&_new->id);
    printf("please enter the gpa\n");
    scanf("%d",&_new->gpa);
    rear->next=_new;
    _new->previous=rear;       
    printf("please enter yes or no\n");
    scanf("%c",&ans);
}while(ans=='y');

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One problem, you aren't reseting rear anywhere in the loop, it remains pointing to the first node (the head) created prior to the loop. _new->previous thus always points to head.