year, month, and day:struct date
{
int year;
int month;
int day;
};cpp" in which you store all your C++ source files: |
... so using this analogy, struct date would look like ... |
 |
Now actually when we're using the
struct keyword in the above example we're not creating any variables. What we're doing is constructing a blue print type dealy FOR making variables. To actually create variables using this "blue print" we simply put the name of the struct you made, followed by the variable you want to create. So it follows this form:[struct type] [variable];So we could create variables using our blue print, by doing something like the following:
date dt;
date md;
date dob;year, month, and day) and then gets user input to fill these variables with values./* -example 1--------------------------------------------------------------- */
#include <iostream.h>
void main()
{
int year, month, day;
cout << "Please input the following: ";
cout << "Year :";
cin >> year;
cout << "Month :";
cin >> month;
cout << "Day :";
cin >> day;
}
/* ------------------------------------------------------------------------- */
/* -example-2--------------------------------------------------------------- */
#include <iostream.h>
struct date
{
int year;
int month;
int day;
};
void main()
{
date dt;
cout << "Please input the following: ";
cout << "Year :";
cin >> dt.year;
cout << "Month :";
cin >> dt.month;
cout << "Day :";
cin >> dt.day;
}
/* ------------------------------------------------------------------------- */
We declared the structure
date to contain three pieces, which of course are year, month, and day. Now then in main() we create a variable called dt using our date structure. In essence this creates those three pieces under that one name. So dt has three pieces that call it momma:
dt
|-- year
|-- month
\-- day
Now we can use these pieces almost just like normal variables. Because that's all they are! They're normal variables just "grouped" under the one object
dt. To access variables within a structure you put the name of the struct followed by a period (.) and then lastly the name of the variable within that you wish to access:[struct].[variable]So say we want to use the
year part of dt: dt.year. Or month: dt.month.How does this become useful to us? Well, what if you want to have the date of birth for three people. You could do it without structs, most definetly. The following is an example of that:
/* -example-3--------------------------------------------------------------- */
#include <iostream.h>
void main()
{
int neil_dob_year, neil_dob_month, neil_dob_day;
int missy_dob_year, missy_dob_month, missy_dob_day;
int jae_dob_year, jae_dob_month, jae_dob_day;
neil_dob_year = 1979;
neil_dob_month= 8;
neil_dob_day = 19;
missy_dob_year = 1977;
missy_dob_month= 10;
missy_dob_day = 30;
}
/* ------------------------------------------------------------------------- */
But this is so unelegant. It requires us to declare many variables even though each person's date of birth contain common things. So below is the same thing except using structs.
/* -example-4--------------------------------------------------------------- */
#include <iostream.h>
struct date;
{
int year, month, day;
}
void main()
{
date neil_dob;
date missy_dob;
date jae_dob;
neil_dob.year = 1979;
neil_dob.month= 8;
neil_dob.day = 19;
missy_dob.year = 1977;
missy_dob.month= 10;
missy_dob.day = 30;
}
/* ------------------------------------------------------------------------- */
y (year), m (month), and d (day). Well, below is a simple example of this.
/* -example-5--------------------------------------------------------------- */
#include <iostream.h>
void print_date(int y, int m, int d);
void main()
{
int year, month, day;
year = 1979;
month= 8;
day = 19;
print_date(year,month,day);
}
void print_date(int y, int m, int d)
{
cout << "The date is: " << m << '/' << d << '/' << y;
}
/* ------------------------------------------------------------------------- */
In
main() we create three integers (year, month, and day). We pass them to print_date() where y becomes what we passed as year, m what we passed as month, etc. And then in the function I simply say, "The date is: month/day/year". This requires that we pass three parameters which can become a hassle. Sometimes its just easier to pass one. So below is the version using a structure.
/* -example-6--------------------------------------------------------------- */
#include <iostream.h>
struct date
{
int year, month, day;
};
void print_date(date d);
void main()
{
date dt;
dt.year = 1979;
dt.month= 8;
dt.day = 19;
print_date(dt);
}
void print_date(date d)
{
cout << "The date is: " << d.month << '/' << d.day << '/' << d.year;
}
/* ------------------------------------------------------------------------- */
