onsdag 13 maj 2020

Structure Part I: The Basics

 

Today we are going to go through Structures from defining structures to using structures.
Structures are just a collection of different types under one roof (you can even put one type only!). So that means they give you flexibility of grouping different data types (like int, char, or even char[]) under one name.
So let us start with obviously defining a Structure. In `C` we declare a structure as simply as this:-
struct dob {
    int day;
    int month;
    int year;
};
1: In the above code segment struct is a keyword which defines structure.
2: Followed by struct keyword (dob) is the name of our structure.
3: Elements of struct are defined inside braces '{}' as we did (int day; etc).
4: After ending brace we place a terminator ';' to end the declaration.

So now you know how to define a structure but how to create its instances now?
To create a variable of our structure we just need to do this:
struct dob date;
This now declares date as a structure variable of type dob.
1: Here 'struct dob' is our above declared structure.
2: date is a variable of type dob.

So ok we have a structure and a variable of that type but how can i access its parts?
well we can access it and assign it so simply like this:-
date.day = 19;date.month = 10;date.year  = 1990;
Note here we use the dot (.) operator to access the fields (parts) of our structure.
ok everything looks nice so for but how in the world can i read data into this structure variable? Again no worries its again simple:-
scanf("%d", &date.day);scanf("%d", &date.month);
that was pretty easy but I was wondering how can i print its data?
Just do it like this:-
printf("Day: %d", date.day);printf("Month: %d",date.month);printf("Year: %d", date.year);
Again remember we use dot (.) operator to access members of a structure.
So we now know how to define and declare a structure, how to access its members, how to read data in it, and how to print data of a structure. Oh that was a tough job..!
Now let us put it together in a single C Program.
/***********************************************/
#include <stdio.h>
struct dob {
   int day;
   int month;
   int year;
};

int main(void) {
  struct dob date;
  date.day = 19;
  date.month = 10;
  date.year = 1990;

  printf("Day is : %d, Month is: %d, and Year is %d\n",
           date.day,date.month, date.year);

  printf("Enter Day, Month, and Year separated by spaces: ");
  scanf("%d %d %d", &date.day,&date.month,&date.year);
  printf("Your entered Date is: %d/%d/%d",
  date.day,date.month,date.year);

  return 0;
}
Output:
Day is : 19, Month is: 10, and Year is 1990
Enter Day, Month, and Year separated by spaces: 1 1 2014
Your entered Date is: 1/1/2014
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