Academic Program

Structures

Structures

Structures are collections of variables grouped together under a common name. The variables within a structure are referred to as the structure’s members and may be accessed individually as needed.

Structures:

  • May contain any number of members
  • Members may be of any data type
  • Allow group of related variables to be treated as a single unit, even if different types
  • Ease the organization of complicated data

Creating a Structure Definition

Syntax

​

struct structName
{
type1 memberName1;
…
typen memberNamen;
}

Example

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// Structure to handle complex numbers
struct complex
{
  float re;    // Real part
  float im;    // Imaginary part
}
Declaring a Structure Variable (Method 1)

Syntax

​

struct structName
{
type1 memberName1;
…
typen memberNamen;
} varName1 ,…, varNamen;

Example

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// Structure to handle complex numbers
struct complex
{
  float re;   
  float im;   
} x, y;        // Declare x and y of type complex

Declaring a Structure Variable (Method 2)

Syntax

​

If structName has already been defined:

struct structName varName1 ,…, varNamen;

Example

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struct complex
{
  float re;   
  float im;   
}       
...
struct complex x, y;    // Declare x and y of type complex
Using a Structure Variable
Syntax
​

structVariableName.memberName

Example
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struct complex
{
float re;
float im;
} x, y; //Declare x and y of type complex
 
int main (void)
{
 x.re = 1.25;        // Initialize real part of x
 x.im = 2.50;         // Initialize imaginary part of x
 y = x;               // Set struct y equal to struct x
...
}
Creating a Structure Type with typedef
Syntax
​

typedef struct structTagoptional
{
type1 memberName1;
…
typen memberNamen;
} typeName;

Example
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// Structure type to handle complex numbers
typedef struct
{
  float re;    // Real part
  float im;    // Imaginary part
} complex;
Declaring a Structure Type Variable
Syntax
​

If typeName has already been defined:

typeName varName1 ,…, varNamen;

The keyword struct is no longer required!

Example
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typedef struct
{
  float re;   
  float im;   
} complex;      
...
complex x, y;  // Declare x and y of type complex
Initializing a Structure Variable at Declaration
Syntax
​

If typeName or structName has already been defined:

typeName varName = {const1 ,…, constn};
 or 
struct structName varName = {const1 ,…, constn};

Example
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typedef struct
{
  float re;   
  float im;   
} complex;      
...
complex x = {1.25, 2.50};  // x.re = 1.25, x.im = 2.50