1 structures unimap sem i - 11/12ekt 120 computer programming
TRANSCRIPT
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Structures
UniMAP SEM I - 11/12 EKT 120 Computer Programming
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Outline Introduction Structure Definitions and
Declarations Initializing Structures Operations on Structures Members Structures as Functions Parameters Array of Structures
UniMAP SEM I - 11/12 EKT 120 Computer Programming
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Introduction Structures
Collection of related data items called components (or members) that are NOT necessarily of the same data type.
Commonly used to define records to be stored in files. Usually the collections of related data item are
characteristics in an object For example:
Object CharacteristicsBook price, number of pages, year publishedCar price, year, model, colourStudent name, matric_no, semester
UniMAP SEM I - 11/12 EKT 120 Computer Programming
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Structure Definition Syntax:
struct StructureTypeName {
structure member declaration list};
Example:struct book {
float fPrice;int iNumPages;int iYear;
};
UniMAP SEM I - 11/12 EKT 120 Computer Programming
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Structure Definition struct information
A struct cannot contain an instance of itself
Can contain a member that is a pointer to the same structure type
A structure definition does not reserve space in memory
Instead creates a new data type used to define structure variables
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Structure Declaration After defining a structure type, we may
declare variables that are of that type. A structure variable declaration requires these elements : keyword struct structure type name a list of variables names separated by commas concluding semicolon
E.g. struct book sBook1;
struct book sMyBook,sHisBook,sHerBook;
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How does it look like in my program?
#include <stdio.h>struct book{
float fPrice;int iNumPages;int iYear;
};int main( )
{struct book sBook1;……
}
#include <stdio.h>struct book{
float fPrice;int iNumPages;int iYear;
} sBook1;
int main( ){
……}
or
struct book sBook1;
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Initializing Structures
struct book sBook1 = {25.50, 690, 2005};ORsBook1.fPrice = 25.50;sBook1.iNumPages = 690;sBook1.iYear = 2005;
dot operator
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Operations on Structures Members
Operation Normal variable Structure member
Read from user
scanf(“%f”, &fPrice);
scanf(“%f”, &sBook1.fPrice);
Assign value fPrice = 25.50; sBook1.fPrice = 25.50;
Print as output printf(“%f\n”, fPrice);
printf(“%f\n”, sBook1.fPrice);
Copy to a variable
fNewPrice = fPrice; fNewPrice = sBook1.fPrice;
Pass value to a function
if(fnFun1(fPrice) > 5)
if(fnFun1(sBook1.fPrice) > 5)
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Multiple Structures Variables
struct book sMyBook, sHisBook, sHerBook;
sMyBook
fPrice
iNumPages
iYear
fPrice
iNumPages
iYear
fPrice
iNumPages
iYear
sHisBook
sHerBook
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Multiple Structures Variablese.g.struct book sMyBook, sHisBook, sHerBook;sMyBook. fPrice = 25.50;sHerBook.fPrice = 10.50;if(sMyBook.fPrice > sHerBook.fPrice)
printf(“My book is more expensive than hers\n”);else
printf(“My book is cheaper than hers\n”);
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Sample Program#include <stdio.h>
struct book { float fPrice; int iNumPages; int iYear;};
int main(){ struct book sMyBook =
{25.50,690,2005}; struct book sHerBook;
printf("Enter book price : "); scanf("%f", &sHerBook.fPrice); printf("Enter number of pages : "); scanf("%d", &sHerBook.iNumPages); printf("Enter year published : "); scanf("%d", &sHerBook.iYear);
printf("My book :\n");printf("%.2f\t%d\t%d\n", sMyBook.fPrice, sMyBook.iNumPages, sMyBook.iYear);printf("Her book :\n");printf("%.2f\t%d\t%d\n", sHerBook.fPrice, sHerBook.iNumPages, sHerBook.iYear);
if(sMyBook.iYear > sHerBook.iYear) printf("My book is the latest publication\n");else printf("Her book is the latest publication\n"); return 0;}
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Structures as Function Parameters
Like variables of any other data type, structure variables can be used as formal and actual function parameters.
In passing structure variables by value to a function, the operating systems makes a copy of the entire structure in the data area of the called function.
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Structures as Function Parameters
……
float fnComputePrice(struct book sBkC); //function prototype
…int main( ){ struct book sBookC;
……………fNewPrice = fnComputePrice(sBookC); //function call……
}float fnComputePrice(struct book sBkC) //function definition
{ …….sBkC.fPrice=sBkC.fPrice + fTax;……return(fBkC.fPrice);
}
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Structures as Function Parameters
A nonvoid function of a structure type can return a structure of that structure type under the function’s name if we use a return statement in the function.
struct book fnRead (); //function prototypeint main( ){ ……….
struct book sB;sB = fnRead( ); //function call……….
}struct book fnRead( ) //function definition{ struct book sBk;
printf(“Enter price:”);scanf(“%f”, &sBk.fPrice);…..return(sBk);
}
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Structures as Function Parameters
If all members of a structure variable are not needed for a function to perform its task, we can pass only the required members.
However, we must specify structure members using the component selection operator.
int fnModifyYear(int iA, int iB, int iYear); //function prototype……..int main( ){ struct book sBkC;
…………….iAvgYear=fnModifyYear(iAa, iBb, sBkC.iYear); //function call…….
}
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Structures as Function Parameters
It is possible to pass structure variables using pointers
int main(){ struct book sB;
………fnRead(&sB); //function call
}void fnRead(struct book *sBk){
printf(“Enter price:”);scanf(“%f”, &sBk->fPrice);printf(“Enter numpages:”);scanf(“%d”, &sBk->iNumPages);…….
}
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Sample Program#include <stdio.h>struct book { float fPrice; int iNumPages; int iYear;};struct book fnRead();void fnPrint(struct book, struct book);void fnCompare(int, int);int main(){ struct book sMyBook =
{25.50,690,2005}; struct book sSheBook; sSheBook=fnRead(); fnPrint(sMyBook , sSheBook); fnCompare(sMyBook.iYear,
sSheBook.iYear); return 0;}
struct book fnRead(){ struct book sHerBook;
printf("Enter book price : "); scanf("%f", &sHerBook.fPrice); printf("Enter number of pages : "); scanf("%d", &sHerBook.iNumPages); printf("Enter year published : "); scanf("%d", &sHerBook.iYear); return(sHerBook);}void fnPrint(struct book sMyBook, struct book
sHerBook){ printf("My book :\n"); printf("%.2f\t%d\t%d\n", sMyBook.fPrice,
sMyBook.iNumPages, sMyBook.iYear); printf("Her book :\n"); printf("%.2f\t%d\t%d\n", sHerBook.fPrice,
sHerBook.iNumPages, sHerBook.iYear);}void fnCompare(int iMyYear, int iSheYear){ if(iMyYear > iSheYear) printf("My book is the latest publication\
n"); else printf("Her book is the latest publication\
n");}
UniMAP SEM I - 11/12 EKT 120 Computer Programming
Sample program2#include <stdio.h>struct student{ char name[50];
char program[5];float gpa;
};void displayInfo(struct student);struct student readInfo();int main(){struct student year1={"Aliana","RK20",3.33};struct student year2;displayInfo(year1);
year2=readInfo();displayInfo(year2);return 0;}void displayInfo(struct student std){ printf("%s\t%s\t%.2f\n",std.name,std.program,std.gpa);}struct student readInfo(){ struct student s;
printf("Enter student name: ");scanf("%s", s.name);printf("Enter program: ");scanf("%s", s.program);printf("Enter gpa: ");scanf("%f", &s.gpa);
return(s);}
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Sample program3#include <stdio.h>struct student{ char name[50];
char program[5];float gpa;
};void displayInfo(struct student);void readInfo(struct student *);int main(){struct student postgrad;
readInfo(&postgrad);displayInfo(postgrad);return 0;}
void displayInfo(struct student std){ printf("%s\t%s\t%.2f\n",std.name,std.program,std.gpa);}void readInfo(struct student *s){
printf("Enter student name: ");scanf("%s", s->name);printf("Enter program: ");scanf("%s", s->program);printf("Enter gpa: ");scanf("%f", &s->gpa);
}
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An Array of Structures Suppose a company has 50 full-time employees.
struct employeeType {
char acFirstName[20]; char acLastName[20]; int iPersonID; char acDeptID[10]; double dYearlySalary; double dMonthlySalary; double dYearToDatePaid; double dMonthlyBonus;
}; struct employeeType asEmployees[50];
UniMAP SEM I - 11/12 EKT 120 Computer Programming
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How it looks like
UniMAP SEM I - 11/12 EKT 120 Computer Programming
[0][1][2]
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.[25]
[26]
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.[48]
[49]
Array of structs asEmployees
asEmployees[2]acFirstNameacLastName
iPersonIDacDeptID
dYearlySalarydMonthlySalarydYearToDatePai
ddMonthlyBonus
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How to access??int iCounter;
for(iCounter = 0; iCounter < 50; iCounter++){
scanf(“%s %s %d %s %lf”, &asEmployees[iCounter].acFirstName, &asEmployees[iCounter].acLastName,&asEmployees[iCounter].iPersonID,&asEmployees[iCounter].acDeptID,&asEmployees[iCounter].dYearlySalary);
asEmployees[iCounter].dMonthlySalary=asEmployees[iCounter].dYearlySalary/12; asEmployees[iCounter].dYearToDatePaid = 0.0; asEmployees[iCounter].dMonthlyBonus = 0.0;
}
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How to access?? Suppose that for a given month the monthly bonuses
are already stored in each employee’s record, and we have to calculate the monthly paycheck and update the yearToDatePaid amount. The following loop computes and prints the employee’s paycheck for the month: double dPayCheck; //variable to calculate the paycheck for(iCounter = 0; iCounter < 50; iCounter++) {
printf(“%s %s”, asEmployees[iCounter].acFirstName, asEmployees[iCounter].acLastName); dPayCheck = asEmployees[iCounter].dMonthlySalary +
asEmployees[iCounter].dMonthlyBonus;
asEmployees[iCounter].dYearToDatePaid = asEmployees[iCounter].dYearToDatePaid + dPayCheck; }
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Arrays in Structures
Example const arraySize = 5;
struct listType
{
int aiListElem[arraySize]; //array containing the list int iListLength; //length of the list
};
struct listType sList;
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How it looks like
struct listTypeaiListElem
iListLength
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Structure Within a Structurestruct nameType {
string acFirst; string acMiddle; string acLast;
}; struct addressType {
string acAddress1; string acAddress2; string acCity; string acState; string acZip;
}; struct dateType{
string acMonth;string acDay; string acYear;
};
struct contactType {
string acPhone; string acCellphone; string acFax; string acPager; string acEmail;
}; struct employeeType {
struct nameType sName; string acEmplID; struct addressType sAddress; struct dateType sHiredate; struct dateType sQuitdate; struct contactType sContact; string acDeptID; double dSalary;
};
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Structure Within a Structure : How to access??
//variable declaration struct employeeType sNewEmployee; //declare 100 employees' records struct employeeType asEmployees[100];
sNewEmployee.dSalary = 45678.00; sNewEmployee.sName.acFirst = "Mary"; sNewEmployee.sName.acMiddle = "Beth"; sNewEmployee.sName.acLast = "Simmons";
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Structure Within a Structure : How to access??
The statementscanf(“%s”, &sNewEmployee.sName.acFirst);
reads and stores a string into sNewEmployee.sName.acFirst.
The statement sNewEmployee.dSalary = sNewEmployee.dSalary *
1.05;
updates the salary of newEmployee
UniMAP SEM I - 11/12 EKT 120 Computer Programming
TQ
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