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struct within a struct

hi there,

i came across this struct code and i noticed that it is declaring itself inside it owns struct.

for example:
i have a struct called abc. and inside this abc struct, there is a declaration of struct abc with a next pointer pointing to it.

struct abc {
        char a[20];
        long b;
        struct abc * next;
}

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may i know how is this possible and what is the purpose for this?

thanks in advance.

phoffric

This is not actually a struct within a struct (or nested struct). next is just a pointer to a struct abc. One common application for this is a single linked list. See, for example, the code in this question:
https://www.experts-exchange.com/questions/23404167/Linked-list-help.html

SOLUTION

DonConsolio

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phoffric

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themrrobert

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gagajanice

ASKER

thank you everyone for the explaination.

phoffric, thanks for the url. very useful to me.

Deepu Abraham

if you try using this:

struct abc {
char a[20];
long b;
struct abc next; //<-----without the pointer (*)
}

you will get an error: 'next' uses undefined struct 'abc' since it is not declared.

Have a look at nested structs:
http://www.exforsys.com/tutorials/c-plus-plus/structure-in-c-part-ii.html