CIS3355

HOW DOES STRUCT WORK?

THE FIRST THINK WE HAVE TO DO IS DECLARE THE STRUCTURE.

                struct PayRoll
                {
                 int empNumber;
                 char name[25];
                 float hours;
                 float payRate;
                 float grossPay;
                };

	HERE WE ARE DECLARING THE STRUCTURE AS 'PAYROLL' AND IT CONTAINS FIVE MEMBERS: empNumber, name, hours, payRate, grossPay.
	HERE WE DON'T DECLARE A VARIABLE, WE ARE ONLY DESCRIBING TO THE COMPILER OF WHAT THE STRUCTURE IS MADE OF, IN OTHER WORDS WE CREATED A NEW DATA TYPE CALL PayRoll. TO DEFINE A VARIABLE OF THE NEW DATA TYPE THAT WE CREATED WE SIMPLY DO THE FOLLOWING:

PayRoll deptHead;

TO DECLARE MORE VARIABLES OF THE NEW CREATED DATA TYPE YOU WILL USE THE SAME FORMAT AS A INDEPENDENT VARIABLE:

PayRoll deptHead,employee, accounting;

BY DOING THIS YOU ARE STATING TO THE COMPILER THAT depHead, employee, and accounting are all the same data type PayRoll. IT WILL LOOK SOMETHING AS FOLLOWS:

deptHead

empNumber
name
hours
payRate
grossPay

foreman

empNumber
name
hours
payRate
grossPay

associate

empNumber
name
hours
payRate
grossPay

	EACH OF THE DECLARE VARIABLES WILL HAVE ITS OWN MEMBERS DECLARED IN THE STRUCTURE.
	IF YOU UNDERSTAND EVERYTHING UP TO THIS POINT THEN YOU ARE READY TO DO A ARRAY OF STRUCTURES. FOR EXAMPLE CONSIDER THE FOLLOWING STRUCTURE:

                struct BookInfo
                 {
                   char title[50];
                   char author[30];
                   char publisher[25];
                   foat price;

                 };

WHAT WE DID WAS CREATE A NEW DATA TYPE CALL BookInfo, NEXT WE ARE GOING TO DECLARE AN ARRAY WITH 20 ELEMENTS CALL bookList.

BookInfo bookList[20];

	FROM HERE EVERYTHING ELSE WORKS MORE OR LESS LIKE A REGULAR ARRAY, bookList[0] WILL BE THE FIRST STRUCTURE OF THE ARRAY.
	SO HOW DO WE ACCESS ANY MEMBER IN THE STRUCTURE ARRAY? WE DO THE FOLLOWING, FOR EXAMPLE TO ACCESS bookList[4] IN TITLE WE WILL USE THE FOLLOWING SYNTAX:

bookList[4].title

THE FOLLOWING WILL BE AN EXAMPLE OF A LOOP OF AN ARRAY TO DISPLAY THE INFORMATION STORE IN EACH ELEMENT:

                for (int index = 0; index < 20; index++)
                     {
                        cout << bookList[index].title <<endl;
                        cout << bookList[index].author <<endl;
                        cout << bookList[index].publisher <<endl;
                        cout << bookList[index].price <<endl;
                     }

AN IMPORTANT THINK TO MENTION HERE IS THAT title, author, publisher, price ARE ALSO ARRAY SO THERE INDIVIDUAL ELEMENTS CAN BE ACCESS TOO.

bookList[2].publisher[3] = 't'

THESE WILL STORE CHARACTER 't' IN publisher WHICH IS A MEMBER OF bookList[2].

HOPEFULLY THESE INFORMATION ABOUT ABSTRACT DATA TYPE STRUCT HELP YOU UNDERSTAND A LITTLE BETTER ABOUT STRUCTURES ARRAYS.

HELPFUL LINKS TO HELPFUL SITES

CIS3355 P. KIRS HOME PAGE

CIS3355

WHAT IS AN ARRAY OF STRUCTS (ABSTRACT DATA TYPE)?

	AN ABSTRACT DATA TYPE IS A DATA TYPE CREATED BY THE PROGRAMMER, AND IS COMPOSED OF ONE OR MORE PRIMITIVE DATA TYPES. THE PROGRAMMER CAN DECIDE WHAT VALUES ARE ACCEPTABLE FOR THE DATA TYPE.
	ONE OF THE RESTRICTION OF AN ARRAY THAT WE HAVE TO DEAL WITH IS THAT ALL THE ELEMENTS OF AN ARRAY NEED TO BE FROM THE SAME DATA TYPE. STRUCTS AVOIDS THIS RESTRICTION.

THIS COULD BE A GOOD EXAMPLE THAT CAN HELP YOU GET A BETTER PICTURE:

SUPPOSE A PROGRAM IS CREATED TO SIMULATE A TWELVE-HOUR CLOCK. THE PROGRAM COULD CONTAIN THREE ADTs: HOURS, MINUTES AND SECONDS. THE RANGE OF VALUES FOR THE HOURS DATA TYPE WOULD BE THE INTERGERS 1 THROUGH 12. THE RANGE OF VALUES FOR THE MINUTES AND SECONDS DATA TYPES WOULD BE 0 THROUGH 59. IF AN HOURS OBJECT IS SET TO 12 AND THEN INCREMENTED, IT WILL THEN TAKE ON THE VALUE 1. LIKEWISE IF A MINUTES OBJECT OR A SECONDS OBJECT IS SET TO 59 AND THEN INCREMENTED, THEY WILL TAKE ON THE VALUE 0.(standard version of Starting Out with C++ 3rd Edition, Tony Gaddis)

This is the sintax use for structures:

struct name

{

variable declaration;

// ... more declarations may follow

};

*What is an array of structs and how does it work?*
DEFINITION & EXAMPLES HOW DOES IT WORK LINKS	THIS WEBSITE WILL HELP YOU UNDERSTAND THE QUESTION ABOVE. IT WILL NOT ONLY PROVIDE YOU WITH THE BASIC DEFINITION, BUT IT WILL GIVE YOU EXAMPLES AND HELPFUL TIPS.