rev='made'/> name='keywords'/> name='author'/> ANURANAN: C Programming: Stuctures

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C Programming: Stuctures

When programming, it is often convenient to have a single name with which to refer to a group of a related values. Structures provide a way of storing many different values in variables of potentially different types under the same name. This makes it a more modular program, which is easier to modify because its design makes things more compact. Structs are generally useful whenever a lot of data needs to be grouped together--for instance, they can be used to hold records from a database or to store information about contacts in an address book. In the contacts example, a struct could be used that would hold all of the information about a single contact--name, address, phone number, and so forth. 

The format for defining a structure is
struct Tag {
Where Tag is the name of the entire type of structure and Members are the variables within the struct. To actually create a single structure the syntax is
struct Tag name_of_single_structure;
To access a variable of the structure it goes
For example:
struct example {
int x; };
le an_example; /* Treating it like a normal variable type
struct exam p except with the addition of struct*/
an_example.x = 33; /*How to access its member s
Here is an example program:
struct database {
int id_number;
t salary;
int age; flo a}; int main() {
employee; /* There is now an employee variable that has
struct database modifiable variables inside it.*/ employee.age = 22;
employee.id_number = 1; employee.salary = 12000.21;
The struct database declares that it has three variables in it, age, id_number, and salary. You can use database like a variable type like int. You can create an employee with the database type as I did above. Then, to modify it you call everything with the 'employee.' in front of it. You can also return structures from functions by defining their return type as a structure type. For instance:
struct database fn();
I will talk only a little bit about unions as well. Unions are like structures except that all the variables share the same memory. When a union is declared the compiler allocates enough memory for the largest data-type in the union. It's like a giant storage chest where you can store one large item, or a small item, but never the both at the same time. 

The '.' operator is used to access different variables inside a union also. 

As a final note, if you wish to have a pointer to a structure, to actually access the information stored inside the structure that is pointed to, you use the -> operator in place of the . operator. All points about pointers still apply. 

A quick example:
#include <stdio.h>
struct xampl {
int x; }; in t{
truct xampl structure;
sstruct xampl *ptr;
ptr = &structure
structure.x = 12
;; /* Yes, you need the & when dealing with
structures and using pointers to them*/
printf( "%d\n", ptr->x ); /* The -> acts somewhat like the * when
does when it is used with pointers
emory address Not "get what that memory
It says, get whatever is at that maddress is"*/ getchar();

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