VC, pointers within a structure

Dave Culle
#1 / 4

pointers within a structure

What would the purpose be for including the 'next' and 'prior' pointers
in a structure like this:

struct media_spec {
char spec_number[20];
char revision;
int eng_notice;
char active;
struct media_spec *next, *prior;

Quote:

};

It's from an old DOS program that uses a binary file of these structures
as a sort of database. I assume the pointers are required for some C
library search function?

drc

Mon, 21 Apr 2003 23:50:28 GMT

Matt Slaughte
#2 / 4

pointers within a structure

A linked list.

Matt

Quote:

> What would the purpose be for including the 'next' and 'prior' pointers
> in a structure like this:

> struct media_spec {
> char spec_number[20];
> char revision;
> int eng_notice;
> char active;
> struct media_spec *next, *prior;
> };

> It's from an old DOS program that uses a binary file of these structures
> as a sort of database. I assume the pointers are required for some C
> library search function?

> drc

Tue, 22 Apr 2003 00:01:20 GMT

Igor Tandetni
#3 / 4

pointers within a structure

Such pointers strongly suggest the structure was intended to be used as a
node in a double-linked list.
--
With best wishes,
Igor Tandetnik

Quote:

> What would the purpose be for including the 'next' and 'prior' pointers
> in a structure like this:

> struct media_spec {
> char spec_number[20];
> char revision;
> int eng_notice;
> char active;
> struct media_spec *next, *prior;
> };

> It's from an old DOS program that uses a binary file of these structures
> as a sort of database. I assume the pointers are required for some C
> library search function?

> drc

Tue, 22 Apr 2003 00:02:46 GMT

DeSilv
#4 / 4

pointers within a structure

Its probably a double linked list.
If you dont know what that is then in few words...
You keep a pointer to one record.. each record point to the one before it
and the one after it.. you can now add a new structure and simply append it
or insert it or whatever you fancy.. this way your list can grow from
nothing to all avail memory

Quote:

> What would the purpose be for including the 'next' and 'prior' pointers
> in a structure like this:

> struct media_spec {
> char spec_number[20];
> char revision;
> int eng_notice;
> char active;
> struct media_spec *next, *prior;
> };

> It's from an old DOS program that uses a binary file of these structures
> as a sort of database. I assume the pointers are required for some C
> library search function?

> drc

Tue, 22 Apr 2003 00:15:31 GMT