Record - Struct

7/28/2019 Record - Struct

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Records (struct)


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Objectives

In this chapter, you will:

Learn about records (struct)

Examine various operations on a struct

Explore ways to manipulate data using a

struct

Learn about the relationship between a struct

and functions Discover how arrays are used in a struct

Learn how to create an array ofstruct items


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Record/Structure

Major limitation of arrays: every element of an

array must be of the same type

Sometimes it is necessary to organise related

data items having different data types

e.g. Student Record:

Name string

ID number integer CGPA float

A unit of such data structure is called a

"record"

STUDENT RECORD

Name Ahmad Al-Bab

ID 1007

CGPA 3.99


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Records (structs)

struct: collection of a fixed number of

components (members), accessed by name

Members may be of different types

Syntax:


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Records (structs) (continued)

A struct is a definition, not a declaration


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Records (structs) (continued)


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Accessing struct Members

The syntax for accessing a structmember is:

The dot (.) is an operator, called the memberaccess operator


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(continued)

To initialize the members ofnewStudent:newStudent.GPA = 0.0;

newStudent.firstName = "John";

newStudent.lastName = "Brown";


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(continued) More examples:

cin >> newStudent.firstName;cin >>newStudent.testScore >> newStudent.programmingScore;

score = (newStudent.testScore +newStudent.programmingScore) / 2;

if (score >= 90)newStudent.courseGrade = 'A';

else if (score >= 80)newStudent.courseGrade = 'B';

else if (score >= 70)newStudent.courseGrade = 'C';

else if (score >= 60)newStudent.courseGrade = 'D';

elsenewStudent.courseGrade = 'F';


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Assignment

Value of one struct variable can be

assigned to anotherstruct variable of the

same type using an assignment statement

The statement:

student = newStudent;

copies the contents ofnewStudent into

student


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Assignment (continued)

The assignment statement:

student = newStudent;

is equivalent to the following statements:

student.firstName = newStudent.firstName;

student.lastName = newStudent.lastName;

student.courseGrade =newStudent.courseGrade;

student.testScore = newStudent.testScore;

student.programmingScore =newStudent.programmingScore;

student.GPA = newStudent.GPA;


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Comparison (Relational Operators)

Compare struct variables member-wise

No aggregate relational operations allowed

To compare the values ofstudent andnewStudent:


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Input/Output


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struct Variables and Functions

A struct variable can be passed as a

parameter by value or by reference

A function can return a value of type struct


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Arrays in structs


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Arrays in structs (continued)


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structs in Arrays


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Structure: Initialization


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Structure: Accessing the element

Structure member operator access via . andbehave like a normal variable.

typedef struct {

int id

char name[30];int semester;float cgpa;

}STUDENT;

STUDENT stud1;//declaration

stud1.id = 1234;

stud1.cgpa = 3.45;

strcpy( stud1.name, "Ahmad Al-Bab");

printf (%s CGPA is %f,stud.name ,stud.cgpa);


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Structure and Array

STUDENT stuAry[50];


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Structure and Array: Example#include

#include

#define size 3typedef struct {

int ID;

float Test1;

} STUDENT;

int main()

{

STUDENT student[3];

int i;

for (i = 0; i < size; i++)

{

scanf ("%d", &student[i].ID);

scanf ("%f", &student[i].Test1);

}

for (i = 0; i < size; i++)

{

printf ("The student ID %d", student[i].ID);

printf ("got test 1 %f \n", student[i].Test1);

}

getch();

return 0;

Global declaration

Local Declaration

Store records

Display records


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Structure and Function

Structure can be the parameter of function

Same concept with passing an array

Can either element of the structure or the whole

structure


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Structure and Function: Example#include

#include

typedef struct {int ID;

float Test1;

} STUDENT;

void readSturcture (STUDENT student []);

int main()

{

STUDENT student[3]; //variable declaration

int i;readSturcture(student);

for (i = 0; i < 3; i++)

{

printf ("ID\tTest1\n");

printf ("%d\t",student[i].ID);

printf ("%6.2f\t",student[i].Test1); }

getch();

return 0;

}

void readSturcture (STUDENT student [])

{

int i;

for (i = 0; i < 3; i++)

{

printf ("enter student ID, Test1 with index %d : ",i);

scanf ("%d",&student[i].ID); }

}

Pass the array structure ofstudent;


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Exercise

Define a data structure STUDENT that can

accommodate the table below.

Initialize three variables std1, std2 and std3

to the values shown in the table below.

ID Name Year CGPA

E2345 Ahmad Al-Bab 6 3.89C1234 James Bomb 5 3.78

M3211 Jay Loh 8 3.67


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Summary

struct: collection of a fixed number of

components

Components can be of different types

Called members

Accessed by name

struct is a reserved word

No memory is allocated for a struct

Memory when variables are declared


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Summary (continued)

Dot (.) operator: member access operator

Used to access members of a struct

The only built-in operations on a struct arethe assignment and member access

struct can be passed by value or reference

A function can return a value of type struct

Record - Struct

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