C++ | Structures | Codecademy

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A structure in C++ stores together data elements under a single name. The data elements, also called data members, can be of different data types.

Syntax

A structure is defined with:

  1. The struct keyword in the beginning.
  2. Curly brackets { } to define the body.
  3. A semicolon ; at the end.
struct name {
  member1_type member1_name;
  member2_type member2_name;
  member3_type member3_name;
};

Example

The example below is a struct with the name coder:

struct
 
coder
 
{
  
long
 id
;
  
char
 name
[
30
]
;
  
char
 username
[
15
]
;
}
;


This structure contains three members:


    

  • id
    • 

  • name
    • 

  • username
    • 





Declaring and Initializing Structure Variables


The members of a structure can be initialized inside the structure definition in C++11 and higher.


An example of declaring and initializing a structure variable:


#
include
 
<iostream>


struct
 
coordinates
 
{
  
int
 x
;
  
int
 y
;
}
;


int
 
main
(
)
 
{


  
  
struct
 
coordinates
 c1
;


  c1
.
x 
=
 
2
;
  c1
.
y 
=
 
2
;


  
  
struct
 
coordinates
 c2 
=
 
{
 
0
,
 
1
 
}
;


  std
::
cout 
<<
 
"x1 = "
 
<<
 c1
.
x 
<<
 
", y1 = "
 
<<
 c1
.
y 
<<
 
"\n"
;
 
  std
::
cout 
<<
 
"x2 = "
 
<<
 c2
.
x 
<<
 
", y2 = "
 
<<
 c2
.
y 
<<
 
"\n"
;
 


  
return
 
0
;
}


The output will look like this:


x1 = 2, y1 = 2
x2 = 0, y2 = 1




Array of Structure


Like other primitive data types, we can create an array of structures.


An example of array of structure:


#
include
 
<iostream>


struct
 
coordinates
 
{
  
int
 x
;
  
int
 y
;
}
;


int
 
main
(
)
 
{
  
struct
 
coordinates
 c
[
4
]
;
  
int
 i
;


  
for
 
(
i 
=
 
0
;
 i 
<
 
4
;
 i
++
)
    std
::
cin 
>>
 c
[
i
]
.
x 
>>
 c
[
i
]
.
y
;


  
for
 
(
i 
=
 
0
;
 i 
<
 
4
;
 i
++
)
 
{
    std
::
cout 
<<
 
"x"
 
<<
 i
+
1
 
<<
 
"="
 
<<
 c
[
i
]
.
x 
<<
 
"\t"
;
    std
::
cout 
<<
 
"y"
 
<<
 i
+
1
 
<<
 
"="
 
<<
 c
[
i
]
.
y 
<<
 
"\n"
;
  
}


  
return
 
0
;
}


Input:


1 0
1 2
1 1
0 2


Output:


x1 = 1  y1 = 0
x2 = 1  y2 = 2
x3 = 1  y3 = 1
x4 = 0  y4 = 2




Nested Structure


A structure’s variable can also be a member of, or nested in, another structure.


In the example below, a DOB structure is nested in a coder structure:


struct
 
coder
 
{
  
long
 id
;
  
char
 name
[
30
]
;
  
char
 username
[
15
]
;
  
struct
 
DOB
 
{
    
int
 month
;
    
int
 day
;
    
int
 year
;
  
}
 d
;
}
 bjarne
;


The d is the structure’s variable for struct DOB and bjarne is the structure variable for struct coder.


Members of a nested structure can be accessed using var1.var2.member1.


Initializing a member of the structure DOB from the example above:


bjarne
.
d
.
day 
=
 
10
;

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