Thread: structures and arrays. Whats the diff?

Structures and arrays are very different.

An array is like a list of data elements, each element is referenced by it's own number. A structure (in C) is a grouping of data elements.

Code:

struct MyStruct {
      int a;
      int b;
};

struct MyStruct Instance;

/* ... */

Instance.a = 6;
Instance.b = Instance.a + 2;

Code:

/* ... */
int array [ 20 ];
array [ 0 ] = 6;
array [ 7 ] = 2552;
/* etc */

Well does this mean that between 2 structure definitions then e.g.,

[code]
struct city1
{
char name[50]
int pop
}
c1;

struct *name;
int pop;
{
c2;

does this mean then, the name is accessed via c1.name and in struct city2 the name is accessed via c2 -> name? I thought these were basically the same except it was a matter of preference, really?

The -> operator is used to access a member of a structure via a pointer. For example:

Code:

struct Structure {
     int a, b;
};

struct Structure reg;
struct Structure *ptr;

/* ... */

reg.a = 6; /* access using dot operator */
ptr->a = 7; /* because it's a pointer we use the -> operator */

For example you may have a function that swaps two structures that takes two pointers to structs. You would use the -> operator rather than the normal dot access operator because they're pointers.

Thanks!

from above:

ptr->a = 7;

note that the -> notation is a shorthand for this

(*ptr).a = 7;

babu..
the most important difference seem to be ignored.
where is quzah ... n all others????????

ok...

while an array can store only similar datatypes (may be user defined or primitive), a structure can store different or same data types. it does not matter whether you store same or dissimilar datatypes in a structure.

for example
int a[10] means an collection of ten integers.
char c[10] ,means a collection of ten characters.
and struct aa { int a; }; struct aa struct_array[10] means an array of ten structures.

AND

struct aa { int a; char b; };
so, a structure may be used as a collection of sililar or dissimilar collection of datatypes.


though both of them share some common features like for example allocation of memory for the elements of an array and a structure are in continuous memory locations.

hope this is clear
ucsbme

Originally posted by ucsbme
the most important difference seem to be ignored.
where is quzah ... n all others????????

Originally posted by rmullen3
Structures and arrays are very different.

An array is like a list of data elements, each element is referenced by it's own number. A structure (in C) is a grouping of data elements.

So how was the most important difference ignored?