Thread: Linked Lists

I have a doubt about linked lists..

Memory for structure variables are allocated only when they are declared.right....
Look at this

Code:

struct stud
           {
                      int a;
                      struct stud* next;
            }s;

memory is allocated for s as it is declared.But again s contains another structure variable declaration (struct stud* next.This can hold a pointer to a variable of type struct stud..
so its size is that much to hold that variable...Since it is a structure variable Its memory is allocated when it is declared using that statement.That pointer should point to another variable of struct stud.So Again that variable contains another declaration and this allocates memory again....This process continues..............

So then what is the size of the variable s.

Is the memory size of an address is specified by OS.Or is it item specific(ie. memory required to hold address of int variable and char variable are different.Or are they same.?
If same my doubt is cleared...

Originally Posted by claudiu

A pointer is not an entire structure, it is just the address of where that structure would reside and it has a fixed size (something like an int).

If you want to check you can print (int)sizeof(struct node*) to check how big the pointer is.

So your struct contains an integer (uninitialized) and a an address of another struct (uninitialized).

Is size of an address is specified byOS.ie is it same for every type of variable.Is it same as the number of address lines of CPU.For ex: if 16 address line ,then address takes two bytes for every type of variable?Am I correct?

Pointer sizes are generally determined by the architecture, not the OS (though I imagine a 32-bit OS on a 64-bit system would produce 32-bit pointers). A 32-bit processor usually has a 32-bit data bus and a 32-bit address bus (this is not always true, but typical in modern desktop processors). Thus, the size of a pointer variable should be 32 bits, or 4 bytes. Like itsme and claudiu, I've never seen 2 different sized pointers, and I'm not sure that that would make sense under most circumstances (anybody have anything to say about far pointers in DOS? I don't remember how they work). Suffice to say, if you use sizeof(some_pointer_variable) instead of hard coding it, you shouldn't care what it is. Let your compiler figure out how much space it needs for this stuff...that's part of it's job.