Question

i do not what is happening in this c program. please explain

Answer 1

//cellinst.c

#include<stdio.h>

struct llist{ //struct is used to group data.
int x,y; //this is the member of the struct.
struct llist *next; //struct member that also struct. here the trick
}; //this struct is used without typedef, so need to repeat "struct" word each time to mention

struct llist *newcell(int x, int y) //declaring struct with "struct" word.
{
struct llist *pt;

pt = (struct llist *) malloc(sizeof(struct llist)); //
pt->x=x; pt->y=y; // -> is used to refer to the variable of another function in this case of a struct
return(pt);
}

main()
{
struct llist *top, *p, *q;

p = newcell(1,1);
top = p; q = p;

p = newcell(3,9);
q->next = p; p-> next = NULL;

p = newcell(2,4);
p->next = top->next; top->next = p;

q = top;
do {
printf("%d %d\n", q->x, q->y);
q = q->next;
}while (q != NULL);
}