C language provides Structure data type to group together different data types.
A structure can even store pointers to other structures, so creating a linked data structure.
Initializing structures
We define an example structure type st:
struct st {
int number;
char *str;
};Initializing the structure within its declaration;
struct st first = {3, "hello"}same with designated initializers:
struct st first = {.str="hello", .number=3}If structure was previously declared we can use Compound literals in C99:
struct st second;
second = (struct st){3, "hello"};
same with designated initializers:
struct st second;
second = {.number=3, .str="hello"};
or member by member:
struct st third;
third.number = 8;
third.str = "bye";
Assigning structures
You can assign one structure to another without problem if they are of same type:
struct st foo = {2, "hello"};
struct st bar;
bar = foo;Assign one struct to another in C
Comparing two structures:
It is needed to compare each member of the structure pair. C does no provide language help for this.
Function returning a structure
function returning a struct in C
How do C compilers implement functions that return large structures
Structures and typedef
Using typedef we can avoid writing struct keyword constantly: Why should we typedef a struct so often in C?
typedef is a better alternative than #define for type declarations: Are typedef and #define the same in c?
on the other side:
Linus rant about typedefs
Linux kernel coding style
E.g:
typedef struct st {int number; char *str;} st_t;
st_t first, second, third;
first = (st_t){3, "hello"}Same with:
typedef struct {int number; char *str;} st_t, *st_p;If we have NESTED STRUCTURES:
struct st {int number; char *str; struct st *next;};
typedef struct st st_t;
...
st_t a, b;
a.next = &b;or
typedef struct st st_t;
struct st {int number; char *str; st_t *next;};
...
st_t a, b;
a.next = &b;
or
typedef struct st {int number; char *str; struct st *next;} st_t;
...
st_t a, b;
a.next = &b;C bit fields
C bit fields
When to use bit-fields in C?
Optimizing memory size of a structure
The Lost Art of C Structure Packing
Why isn't sizeof for a struct equal to the sum of sizeof of each member?
Data Structure Alignment