1 Structures UniMAP SEM I - 11/12EKT 120 Computer Programming

2 Outline Introduction Structure Definitions and Declarations Initializing Structures Operations on Structures Members Structures as Functions Parameters Array of Structures UniMAP SEM I - 11/12EKT 120 Computer Programming

3 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 Characteristics Book price, number of pages, year published Car price, year, model, colour Student name, matric_no, semester UniMAP SEM I - 11/12EKT 120 Computer Programming

4 Structure Definition Syntax: struct StructureTypeName { structure member declaration list }; Example: struct book { float fPrice; int iNumPages; int iYear; }; UniMAP SEM I - 11/12EKT 120 Computer Programming

UniMAP SEM I - 11/12EKT 120 Computer Programming 5 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

6 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; UniMAP SEM I - 11/12EKT 120 Computer Programming

7 How does it look like in my program? #include struct book { float fPrice; int iNumPages; int iYear; }; int main( ) { struct book sBook1; …… } #include struct book { float fPrice; int iNumPages; int iYear; } sBook1; int main( ) { …… } or struct book sBook1; UniMAP SEM I - 11/12EKT 120 Computer Programming

8 Initializing Structures struct book sBook1 = {25.50, 690, 2005}; OR sBook1.fPrice = 25.50; sBook1.iNumPages = 690; sBook1.iYear = 2005; dot operator UniMAP SEM I - 11/12EKT 120 Computer Programming

9 Operations on Structures Members OperationNormal variableStructure member Read from userscanf(“%f”, &fPrice);scanf(“%f”, &sBook1.fPrice); Assign valuefPrice = 25.50;sBook1.fPrice = 25.50; Print as outputprintf(“%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) UniMAP SEM I - 11/12EKT 120 Computer Programming

10 Multiple Structures Variables struct book sMyBook, sHisBook, sHerBook; sMyBook  fPrice  iNumPages  iYear  fPrice  iNumPages  iYear  fPrice  iNumPages  iYear sHisBook sHerBook UniMAP SEM I - 11/12EKT 120 Computer Programming

11 Multiple Structures Variables e.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”); UniMAP SEM I - 11/12EKT 120 Computer Programming

12 Sample Program #include 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; } UniMAP SEM I - 11/12EKT 120 Computer Programming

13 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. UniMAP SEM I - 11/12EKT 120 Computer Programming

14 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); } UniMAP SEM I - 11/12EKT 120 Computer Programming

15 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 prototype int 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); } UniMAP SEM I - 11/12EKT 120 Computer Programming

16 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 ……. } UniMAP SEM I - 11/12EKT 120 Computer Programming

17 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); ……. } UniMAP SEM I - 11/12EKT 120 Computer Programming

18 Sample Program #include 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 - 11/12EKT 120 Computer Programming

Sample program2 #include 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); } 19

Sample program3 #include 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); } 20

21 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 - 11/12EKT 120 Computer Programming

22 How it looks like UniMAP SEM I - 11/12EKT 120 Computer Programming [0] [1] [2]... [25] [26]... [48] [49] Array of structs asEmployees asEmployees[2] acFirstName acLastName iPersonID acDeptID dYearlySalary dMonthlySalary dYearToDatePaid dMonthlyBonus

23 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; } UniMAP SEM I - 11/12EKT 120 Computer Programming

24 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; } UniMAP SEM I - 11/12EKT 120 Computer Programming

25 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; UniMAP SEM I - 11/12EKT 120 Computer Programming

26 How it looks like struct listType aiListElem iListLength UniMAP SEM I - 11/12EKT 120 Computer Programming

27 Structure Within a Structure struct 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 ac ; }; struct employeeType { struct nameType sName; string acEmplID; struct addressType sAddress; struct dateType sHiredate; struct dateType sQuitdate; struct contactType sContact; string acDeptID; double dSalary; }; UniMAP SEM I - 11/12EKT 120 Computer Programming

28 Structure Within a Structure : How to access?? //variable declaration struct employeeType sNewEmployee; //declare 100 employees' records struct employeeType asEmployees[100]; sNewEmployee.dSalary = ; sNewEmployee.sName.acFirst = "Mary"; sNewEmployee.sName.acMiddle = "Beth"; sNewEmployee.sName.acLast = "Simmons"; UniMAP SEM I - 11/12EKT 120 Computer Programming

29 Structure Within a Structure : How to access?? The statement scanf(“%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 - 11/12EKT 120 Computer Programming

TQ 30 UniMAP SEM I - 11/12EKT 120 Computer Programming