Structures

A facility for grouping data into composite forms. A collection of related elements, possible of different types.

struct fraction {
	int numerator;
	int denominator;
};

Usage:

struct fraction f1, f2;
f1.numerator = 22;
f1.denominator = 7;

f2 = f1; // copies over the whole struct

There are three ways to declare or define a structure:

1. Variable structure
   • Cannot be passed to functions
   • This structure is a single variable

      struct {
       int a;
       int b;
      } foo;
     

2. Tagged structure

   struct student {
    int id;
    char name[26];
    int gradepoints;
   };
   

3. Type defined

   typedef struct {
    type1 fieldName1;
    type2 fieldName2;
    ...
    typeN fieldNameN;
   }tagName;
   

Pointers to structures

`typedef struct {
	int x;
	int y;
	float t;
	char u;
} SAMPLE;

SAMPLE sam1;
SAMPLE *pt;

ptr = &sam1;
(*ptr).y  == sam1.y


ptr->y // Name of pointer -> name of the field

Nesting structure

typedef struct {
	int month;
	int day;
	int year;
} DATE;

typedef struct {
	int hours;
	int min;
	int sec;
} TIME;

typedef struct {
	DATE date;
	TIME time;
} STAMP;

STAMP stamp; 

Arrays

A simple type of array in C is one that is declared in place. There are more complication use that are related to pointers.

int scores[100]; //0 to 99 hold 100 integers