biggest volume of box in list and given number

#include <iostream>
#include <ctime>
#include <cstdlib>
#include <cmath>

using namespace std;

typedef struct box {
    double length;
    double width;
    double height;
    box *next;
}
BOX;

void addbox(BOX *start)
{
    BOX *t1 = start;
    while(1)
    {
        if (t1 -> next == NULL) break;
        t1 = t1-> next;
    }

    BOX *newbox = new BOX;
    t1 -> next = newbox;
    newbox -> next = NULL;
    newbox -> height = rand()%81+20;
    newbox -> length = rand()%120+10;
    newbox -> width = rand()%90+4;
}



double volumebig(BOX *start)
{
    BOX *t1 = start;
    double big = 0;
    while(1)
    {
        if (t1->next == NULL) break;
        t1 = t1->next;
        if ((t1->height * t1->width * t1->length)>big) big=(t1->height * t1->width * t1->length);
    }
    return big;
}



double volume_over_given(BOX *start, double biggest)
{
    BOX *t1 = start;
int n=0;
    while(1)
    {
        if (t1->next == NULL) break;
        t1 = t1->next;
     if ((t1->height * t1->width * t1->length)>biggest)   n++;
    }
   return n;
    }

void display_parameters(BOX *start)
{
    BOX *t1 = start;
    while(1)
    {
        if (t1->next == NULL) break;
        t1 = t1->next;
    }
        cout<<""<<t1->height<<endl;
        cout<<""<<t1->width<<endl;
        cout<<""<<t1->length<<endl;
        cout<< ""<<(t1->height * t1->width * t1->length)<<endl;
}

int main()
{
    srand(time(NULL));
    BOX *box0 = new BOX;



    for (int i = 0; i < 10; i++) {
        addbox(box0);
    display_parameters(box0);
    }
        cout<<"Biggest volume="<< volumebig(box0)<<endl;
cout<<"volume over given number="<<volume_over_given(box0,100000);
    return 0;
}