Transcript Introduction to Computer Programming Concepts.

User Defined Data Types Structures in C
CHAPTER 4
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Structures
» An ARRAY allow the programmer to define variables
that associated several data items of the same kind.
» A STRUCTURE allow the programmer to define
variables that associated several data items of different
kind.
» The STRUCTURE in C is similar to the RECORD in
languages such as Pascal (Delphi), COBOL.
» Each student Identity structure (record) is containing
some members (fields) like, “student_no”, “name”,
“birth_date”, …)
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Defining a Structure
» A structure is defined in terms of members (fields).
struct tag {
member 1;
member 2;
…
member n;
};
» struct is a key word.
» tag is a name that identify the structures having this
composition.
» member 1, … , member n are individual member
declarations.
» Members can be ordinary variables, pointers, arrays or
other structures.
» Member names within the particular structure must be
distinct from one another.
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Defining a Structure
» Member names can be same as the name of a variable
defined outside of the structure, or with the name of a
member defined under a different structure (not
preferred).
» Once the composition of a structure has been defined,
individual structure type variables can be declared as
follows:
struct tag variable 1, variable 2, … , variable n;
» Where variable 1, …, variable n are variables that are
declared in struct tag data type.
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Defining
a
Structure
» Example :
struct account {
int acct_no;
char acct_type;
char acct_name[81];
float balance;
};
struct account oldcustomer, newcustomer;
The oldcustomer and the newcustomer are variables of
type account. (They are called structure-type variables).
» It is possible to combine the declaration of the structure
composition with that of the structure-variables.
struct account {
int acct_no;
char acct_type;
char acct_name[81];
float balance;
} oldcustomer, newcustomer;
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Defining a Structure
» A structure may also be defined as the member of
another structure.
»In this case the declaration of the embedded structure
must come before the declaration of the container
structure.
»e.g :
struct date {
int day;
int month;
int year;
};
struct account {
int acct_no;
char acct_type;
char acct_name[81];
float balance;
struct date lastpayment;
} oldcustomer, newcustomer;
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Defining a Structure
» On the following example, the structure account is
containing another structure date as one of its member.
»e.g :
struct date {
int day, month, year;
};
struct account {
int acct_no;
char acct_type;
char acct_name[81];
float balance;
struct date firstpayment;
struct date lastpayment;
} oldcustomer, newcustomer;
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Initializing a Structure
struct date {
int day, month, year;
};
struct account {
int acct_no;
char acct_type;
char acct_name[81];
float balance;
struct date lastpayment;
};
struct account customer = {12345, ‘R’, “Salaries”, 500.3, 28, 5, 2002};
» customer is a structure variable of type account.
» Assignments:
acct_no = 12345, acct_type = ‘R’,
acct_name = “Salaries”
balance = 500,3
lastpayment (day = 28, month = 5, year = 2002)
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Array of Structure
»It is possible to define an array of structures.
struct date {
int day, month, year;
};
struct account {
int acct_no;
char acct_type;
char acct_name[81];
float balance;
struct date lastpayment;
} customer[100];
» In this example, the customer is declared as an array of
struct account with 100 elements.
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Array of Structure
»An array of structures can be initialized just as any othe
array can be.
struct date {
char name[21];
int day, month, year;
};
struct date birthdate[3] = { “Ali”,
20, 7, 1974,
“Ayse”, 18, 1, 1982,
“Fatma”, 8, 12, 1983 };
or
struct date birthdate[3] = { {“Ali”,
20, 7, 1974},
{“Ayse”, 18, 1, 1982},
{“Fatma”, 8, 12, 1983}
};
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Processing a Structure
»The members of the structures must be accessed and
processed separately.
variable.member
»variable : name of the structure-type variable.
»member : The name of the member within the structure.
»The period (.) is an operator of highest priority and has
left-to-right associatively.
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Processing a Structure
e.g:
struct date {
int day, month, year;
};
struct account {
int acct_no;
char acct_type;
char acct_name[81];
float balance;
struct date lastpayment;
} customer;
…
customer.acct_no = 1221;
// sets cursomer’s account no to 1121
customer.balance = 0;
// sets cursomer’s balance to 0
printf(“%s”,customer.acct_name); // displays the cursomer’s account name
++customer.balance;
// Increments the customer’s balance by one
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Processing a Structure
e.g (continuing) :
scanf(“%d”,&customer.lastpayment.year);
// reading the cursomer’s last payment date year
printf(“Last Payment : %2d-%2d-%d “,
customer.lastpayment.day,
customer.lastpayment.month,
customer.lastpayment.year);
// displays the last payment date of the customer
printf(“%c”,customer.acct_name[2]);
// displays the 3rd character of the cursomer’s account name
customer.acct_type=‘I’;
// Sets the account type of the customer to ‘I’.
total + = customer.balance;
// Adds the balance of the customer to the variable “total”
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Processing a Structure
e.g :
struct date {
int day, month, year;
};
struct account {
int acct_no;
char acct_type;
char acct_name[81];
float balance;
struct date lastpayment;
} customer[100];
…
customer[13].balance=0;
// Sets the balance of the 14th customer to 0.
++customer[5].lastpayment.day;
// Incrementing the last payment date by one day of the 6th customer.
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Example
Problem: Write a program including structures to read mt,
final and quiz scores of the class with 25 students and will
display the score list of the class with total grade of each
student and the average of the class.
Note that, each student has to have a record with the following fields in the
class:
std_no
(Student Number)
std_name
(Student Name)
mt
(Midterm Score)
final
(Final Score)
quiz
(Quiz Score)
grd
(Total Grade)
The weights of the scores are given as:
30 % Midterm,
50% Final, and
20% Quiz
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Example
#include <stdio.h>
#include <conio.h>
struct student {
char stdno[7];
char name[21];
int mt, final, quiz;
float grd; };
1.
void main()
{
struct student c213[2];
int totscores[3]={0,0,0}, i;
float totgrd=0;
char blank[2];
// Reading Student Information
2.
for (i=0; i< 2; i++)
{
clrscr();
printf("\n%4d. Student Data Entry\n\n", i+1);
printf("\n Student No :"); gets(c213[i].stdno);
printf("\n Student Name :"); gets(c213[i].name);
printf("\n Midterm Score:");
scanf("%d",&c213[i].mt);
printf("\n Final Score:");
scanf("%d",&c213[i].final);
printf("\n Quiz Score:");
scanf("%d",&c213[i].quiz);
gets(blank);
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Example
c213[i].grd = 0.30*c213[i].mt + 0.50*c213[i].final
3.
+ 0.20*c213[i].quiz;
totscores[0]+=c213[i].mt; // Midterm Scores Total
totscores[1]+=c213[i].final; // Final Scores Total
totscores[2]+=c213[i].quiz; // Quiz Scores Total
totgrd+= c213[i].grd;
// Grades total
}
// Displaying the Class Scores List
clrscr();
printf("\n Class Scores List\n\n");
printf("\n STD_NO NAME
MT FIN QUI GRADE");
printf("\n===================================================");
for (i=0; i< 2; i++)
{
printf("\n%7s %20s %3d %3d %3d %6.2f",
c213[i].stdno,c213[i].name, c213[i].mt,
c213[i].final, c213[i].quiz, c213[i].grd);
}
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Example
4.
// The Score Averages part of the List
printf("\n===================================================");
printf("\nAverages
%3d %3d %3d %6.2f",
totscores[0]/2, totscores[1]/2,
totscores[2]/2, totgrd/2);
getch();
}