Struct
Define user-defined type with struct
Class in C++ is an extension of struct
Define a Type with Struct
// Car.h
#ifndef CAR_H
#define CAR_H
struct Car{
int year;
int cylinder;
};
#endif
// main.c
#include <stdio.h>
#include "Car.h"
int main()
{
struct Car c;
c.year = 2016;
c.cylinder = 4;
printf("Year: %d\n", c.year);
printf("Cylinder: %d\n", c.cylinder);
return 0;
}
Define a Type with Struct and Typedef
// Car.h
#ifndef CAR_H
#define CAR_H
typedef struct
{
int year;
int cylinder;
} Car;
#endif
// main.c
#include <stdio.h>
#include "Car.h"
int main()
{
Car c;
c.year = 2016;
c.cylinder = 4;
printf("Year: %d\n", c.year);
printf("Cylinder: %d\n", c.cylinder);
return 0;
}
Copy a Struct
Copying a struct means copying every element from one struct to another
// Car.h
#ifndef CAR_H
#define CAR_H
typedef struct
{
int year;
int cylinder;
} Car;
#endif
// main.c
#include <stdio.h>
#include "Car.h"
int main()
{
Car c;
c.year = 2016;
c.cylinder = 4;
Car temp;
temp = c;
printf("Year: %d\n", temp.year);
printf("Cylinder: %d\n", temp.cylinder);
return 0;
}
Pass Struct by Value to Function
Pass a struct to a function by value, make a copy in the function
Retun a struct, return a copy
// Car.h
#ifndef CAR_H
#define CAR_H
typedef struct {
int year;
int cylinder;
} Car;
#endif
// main.c
#include <stdio.h>
#include "Car.h"
Car getCar()
{
Car car;
car.year = 2016;
car.cylinder = 4;
return car;
}
void display(Car car)
{
printf("Year: %d\n", car.year);
printf("Cylinder: %d\n", car.cylinder);
}
int main()
{
Car c;
c = getCar();
display(c);
return 0;
}
Pass Struct by Reference to Function
// Car.h
#ifndef CAR_H
#define CAR_H
typedef struct
{
int year;
int cylinder;
} Car;
#endif
#include <stdio.h>
#include "Car.h"
void getCar(Car *car)
{
//(*car).year = 2016;
//(*car).cylinder = 4;
car->year = 2016;
car->cylinder = 4;
}
void display(Car *car)
{
printf("Year: %d\n", car->year);
printf("Cylinder: %d\n", car->cylinder);
}
int main()
{
Car c;
getCar(&c);
display(&c);
return 0;
}
Use Struct in Array
// Car.h
#ifndef CAR_H
#define CAR_H
typedef struct
{
int year;
int cylinder;
} Car;
#endif
#include <stdio.h>
#include "Car.h"
void setCars(Car cars[], int size)
{
cars[0].year = 2016;
cars[0].cylinder = 4;
cars[1].year = 2005;
cars[1].cylinder = 6;
cars[2].year = 1999;
cars[2].cylinder = 6;
}
void sort(Car cars[], int size)
{
for (int i = 0; i < size-1; i++)
for (int j = 0; j < size-i-1; j++)
if (cars[j].year > cars[j+1].year)
{
Car temp = cars[j];
cars[j] = cars[j+1];
cars[j+1] = temp;
}
}
void display(Car cars[], int size)
{
for(int i = 0; i < size; i++)
{
printf("Year: %d\n", cars[i].year);
printf("Cylinder: %d\n\n", cars[i].cylinder);
}
}
int main()
{
Car cars[3];
setCars(cars, 3);
display(cars, 3);
sort(cars, 3);
display(cars, 3);
return 0;
}
Use Struct in Pointer Array
#ifndef CAR_H
#define CAR_H
typedef struct
{
int year;
int cylinder;
} Car;
#endif
#include <stdio.h>
#include <stdlib.h>
#include "Car.h"
Car *getCars()
{
Car *cars = (Car *) malloc(3*sizeof(Car));
cars[0].year = 2016;
cars[0].cylinder = 4;
cars[1].year = 2005;
cars[1].cylinder = 6;
cars[2].year = 1999;
cars[2].cylinder = 6;
return cars;
}
void sort(Car *cars, int size)
{
for (int i = 0; i < size-1; i++)
for (int j = 0; j < size-i-1; j++)
if (cars[j].year > cars[j+1].year)
{
Car temp = cars[j];
cars[j] = cars[j+1];
cars[j+1] = temp;
}
}
void display(Car *cars, int size)
{
for(int i = 0; i < size; i++)
{
printf("Year: %d\n", cars[i].year);
printf("Cylinder: %d\n\n", cars[i].cylinder);
}
}
int main()
{
Car *cars;
cars = getCars();
display(cars, 3);
sort(cars, 3);
display(cars, 3);
return 0;
}
Struct Composition
#ifndef WHEEL_H
#define WHEEL_H
typedef struct{
float price;
} Wheel;
#endif
#ifndef CAR_H
#define CAR_H
#include "Wheel.h"
typedef struct{
Wheel wheel;
int year;
int cylinder;
} Car;
#endif
#include <stdio.h>
#include <stdlib.h>
#include "Car.h"
int main()
{
Car car;
car.wheel.price = 100;
car.year = 2016;
car.cylinder = 4;
printf("Year: %d\n", car.year);
printf("Cylinder: %d\n", car.cylinder);
printf("Wheel price: %.2f\n", car.wheel.price);
return 0;
}
Array in Struct
// Student.h
#ifndef STUDENT_H
#define STUDENT_H
typedef struct
{
char name[20];
int grades[5];
} Student;
#endif
#include <stdio.h>
#include <string.h>
#include "Student.h"
int getGrade()
{
int grade;
printf("Entery grade:");
scanf("%d", &grade);
return grade;
}
int main()
{
Student s;
strcpy(s.name, "Lin"); // why not s.name = "Lin"
for(int i = 0; i < 5; i++)
s.grades[i] = getGrade();
printf("Name: %s\n", s.name);
for(int i = 0; i < 5; i++)
printf("Grade: %d\n", s.grades[i]);
return 0;
}
Pointer Member
#ifndef STUDENT_H
#define STUDENT_H
typedef struct
{
int num; // number of exames
int *grades;
} Student;
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "Student.h"
void display(Student s)
{
for(int i = 0; i < s.num; i++)
printf("Grade: %d\n", s.grades[i]);
}
int main()
{
Student s;
s.num = 3;
s.grades = (int *) malloc(s.num*sizeof(int));
s.grades[0] = 100;
s.grades[1] = 95;
s.grades[2] = 90;
display(s);
Student s2;
s2 = s;
display(s2);
s.grades[0] = 60;
display(s2);
return 0;
}
#ifndef STUDENT_H
#define STUDENT_H
typedef struct
{
int num; // number of exames
int *grades;
} Student;
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "Student.h"
void display(Student s)
{
for(int i = 0; i < s.num; i++)
printf("Grade: %d\n", s.grades[i]);
}
void setS(Student *s)
{
s->num = 3;
s->grades = (int *) malloc(s->num*sizeof(int));
s->grades[0] = 100;
s->grades[1] = 95;
s->grades[2] = 90;
}
void copy(Student *dest, Student *source)
{
dest->num = source->num;
dest->grades = (int *) malloc(source->num*sizeof(int));
memcpy(dest->grades, source->grades, source->num*sizeof(int));
}
int main()
{
Student s;
setS(&s);
display(s);
Student s2;
copy(&s2, &s);
display(s2);
s.grades[0] = 60;
display(s2);
return 0;
}
Union
#include
#include
union Employee
{
// age and hours share the same memory
int age;
int hours;
};
int main()
{
union Employee e;
e.age = 39;
e.hours = 40;
printf("%d: %d\n", e.hours, e.age); // 40 40
return 0;
}
