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Structures

Structures. Introduction.  Although arrays greatly improved our ability to store data, there is one major drawback to their use each element (each box) in an array must be of the same data type A structure is a collection of variable types grouped together or

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Structures

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  1. Structures

  2. Introduction •  Although arrays greatly improved our ability to store data, there is one major drawback to their use • each element (each box) in an array must be of the same data type • A structure is a collection of variable types grouped together or • A structure is a collection of heterogeneous data types grouped together to form a single data type • You can refer to a structure as a single variable, and to its parts as members of that variable • Members are accessed by using the dot (.) operator following the structure variable

  3. Cont’d… • The power of structures lies in the fact that once defined, the structure name becomes a user-defined data type and may be used the same way as other built-in data types, such as int, double, char, … • The format for defining a structure is: struct Tag { Members }; • Where Tag is the name of the entire type of structure • Members are the variables or data fields within the struct

  4. Structure Tag or Structure Name • Examples… struct employee { intid_number; int age; float salary; } emp; struct employee { intid_number; int age; float salary; } emp1, emp2, emp3; Members/Fields of the structure Structure variable Three different Structure variables

  5. struct employee { intid_number; int age; float salary; }; employee emp1, emp2, emp3; struct date{ int day; int month; int year; }; Three different Structure variables

  6. Arrays vs Structures • The difference between arrays and structures is that: • The elements of an array are of the same type(homogeneous) while the elements of a structure which are know as members or fields are of different types(heterogeneous) • Each element of an array is referred by its position(index) which each element of a structure referred by its name(has a unique name)

  7. Accessing array elements vs structure fields #include<iostream.h> #include<conio.h> struct number { int x; float y; char ch; }num = {15, 3.5, 'A'}; void main() { cout<<"x = "<<num.x<<", y = "<<num.y<<", ch = "<<num.ch<<endl; int num[3] = { 4, -6,10}; cout<<"num[0]= "<<num[0]<<", num[1]= "<<num[1]<<", num[2]= "<<num[2]<<endl; getch(); } Output x = 15, y = 3.5, ch = A num[0]= 4, num[1]= -6, num[2]= 10 Structure initialization

  8. Structure initialization // A structure to record and display date #include<iostream.h> #include<conio.h> struct date{ int day; int month; int year; }; date today; void main() { today.day = 28; today.month = 8; today.year = 2013; cout<<"\nToday's date is: "<<today.day<<'/'<<today.month<<'/'<<today.year; getch(); } Output Today's date is: 28/8/2013

  9. Reading the data fields Output Enter the day: 15 Enter the month: 7 Enter the year: 2012 Today's date is: 15/7/2012 //Reading data field values from the keyboard #include<iostream.h> #include<conio.h> struct date{ int day; int month; int year; }; date today; void main() { cout<<"\n Enter the day: "; cin>>today.day; cout<<"\n Enter the month: "; cin>>today.month; cout<<"\n Enter the year: "; cin>>today.year; cout<<"\nToday's date is: "<<today.day<<'/'<<today.month<<'/'<<today.year; getch(); }

  10. Structures and pointers • If you wish to have a pointer to a structure, to actually access the information stored inside the structure that is pointed to, you use the -> operator in place of the dot ( . ) operator #include<iostream.h> #include<conio.h> struct example { int x; }; void main() { example *ptr = new example; ptr->x = 12; cout<<"  x = "<<ptr->x<<endl; cout<<" x = "<<(*ptr).x<<endl; getch(); } Output x = 12 x = 12

  11. Cont’d… #include<iostream.h> #include<conio.h> struct bal { char name[30]; float balance; }person; int main() { bal *p= new bal; cout<<"Customer name: "; cin>>p->name; cout<<"Customer balance: "; cin>>p->balance; cout<<"\n Customer Info\n"; cout<<"Customer name\t Balance\n"; cout<<p->name<<"\t\t"<<p->balance<<endl; getch(); return 0; } Sample Run Customer name: Abebe Customer balance: 1500 Customer Info Customer name Balance Abebe 1500

  12. Examples (pointers and Structure …) // A simple program involving structure of items #include<iostream.h> #include<conio.h> struct item { intitemCode; char itemName[20]; int qty; float unitPrice; }; item *p;

  13. Cont’d… void main() { p = new item; cout<<"\nItem code: "; cin>>p->itemCode; //cin>>(*p).itemCode cout<<"\nItem Name: "; cin>>p->itemName; //cin>>(*p).itemName cout<<"\nItem Quantity: "; cin>>p->qty; //cin>>(*p).qty cout<<"\nItem unit price: "; cin>>p->unitPrice; //cin>>(*p).unitPrice cout<<"\nItem Code\t Item Name \t Quantity \t Unit Price\t Total Price\n"; cout<<p->itemCode<<"\t\t"<<p->itemName<<"\t\t"<<p->qty<<"\t\t"<< p->unitPrice<<"\t\t"<<p->qty*p->unitPrice<<endl; getch(); }

  14. Cont’d… Output Item code: 101 Item Name: Sugar Item Quantity: 200 Item unit price: 15 Item Code Item Name Quantity Unit Price Total Price 101 Sugar 200 15 3000

  15. The same example with different style of pointer void main() { p = new item; cout<<"\nItem code: "; cin>>(*p).itemCode; //p->itemCode; cout<<"\nItem Name: "; cin>>(*p).itemName; //cin>>p->itemName; cout<<"\nItem Quantity: "; cin>>(*p).qty; //cin>>p->qty; cout<<"\nItem unit price: "; cin>>(*p).unitPrice; //cin>>p->unitPrice; cout<<"\nItem Code\t Item Name \t Quantity \t Unit Price\n"; cout<<(*p).itemCode<<"\t\t"<<(*p).itemName<<"\t\t"<<(*p).qty<<"\t\t"<<(*p).unitPrice<<endl; getch(); }

  16. Structures and Functions • We can use functions to write a modular program and access structure variables #include<iostream.h> #include<conio.h> struct student { char name[20]; int age; char gender; }; student stud1,stud2; void getStudent(); void printStudent(); void main() { getStudent(); printStudent(); getch(); } Function prototypes/Function declarations

  17. Cont’d… void getStudent() { cout<<"\n Enter name of the first student: "; cin>>stud1.name; cout<<"\n Enter age of the first student: "; cin>>stud1.age; cout<<"\n Enter gender of the first student: "; cin>>stud1.gender; cout<<"\n Enter name of the second student: "; cin>>stud2.name; cout<<"\n Enter age of the second student: "; cin>>stud2.age; cout<<"\n Enter gender of the second student: "; cin>>stud2.gender; } void printStudent() { cout<<"\nStudent Information\n"; cout<<"Name\tAge\tGender\n"; cout<<stud1.name<<'\t'<<stud1.age<<'\t'<<stud1.gender<<endl; cout<<stud2.name<<'\t'<<stud2.age<<'\t'<<stud2.gender<<endl; }

  18. Cont’d… Sample Run of the previous program Enter name of the first student: Abebe Enter age of the first student: 23 Enter gender of the first student: M Enter name of the second student: Hirut Enter age of the second student: 21 Enter gender of the second student: F Student Information Name Age Gender Abebe 23 M Hirut 21 F

  19. Arrays of Structures • Structure corresponds to records of a database • One can specify the number of records of a structure in an array form: struct student { char name[20]; int age; char gender; }; student st1,st2,st3,st4,st5; student stud[5]; Five structure variables Array of structure variable of size 5

  20. … Arrays of Structures #include<iostream.h> #include<conio.h> const int max=100; struct employee{ char empID[10]; char empName[20]; float salary; //unit price }; employee emp[max]; int n; void getEmployee(); void printReport(); float netSalary(float); void main() { getEmployee(); printReport(); getch();

  21. …Cont’d void getEmployee() { char ans; n=0; do{ cout<<"\n Employee ID: "; cin>>emp[n].empID; cout<<"\n Employee Name: "; cin>>emp[n].empName; cout<<"\n Salary: "; cin>>emp[n].salary; n++; cout<<"\n Any more employees? y/n: "; cin>>ans; }while(ans=='y' || ans=='Y'); }

  22. Cont’d… float netSalary(float bs) { float tax,pension; pension = bs*0.06; if(bs<=150) tax = 0; else if(bs<=650) tax = (bs-150)*0.1; else if(bs<=1400) tax = 50+(bs-650)*0.15; else if(bs<=2350) tax = 162.5+(bs-1400)*0.2; else if(bs<=3500) tax = 352.5+(bs-2350)*0.25; else if(bs<=5000) tax = 640+(bs-3500)*0.3; else if(bs>5000) tax = 1090+(bs-5000)*0.35; return bs-(tax + pension); } void printReport() { cout<<"\n Employee Info\n\n"; cout<<"\n ID\t\t Name \t\t Basic Salary \t Net Salary\n"; for(inti=0; i<n; i++) cout<<emp[i].empID<<"\t\t"<<emp[i].empName<<"\t\t"<<emp[i].salary<<"\t\t"<<netSalary(emp[i].salary)<<endl; }

  23. Cont’d… Employee ID: emp01 Employee Name: Dawit Salary: 2500 Any more employees? y/n: y Employee ID: emp02 Employee Name: Aster Salary: 3000 Any more employees? y/n: y Employee ID: emp04 Employee Name: Rahel Salary: 1500 Any more employees? y/n: n Employee Info ID Name Basic Salary Net Salary emp01 Dawit 2500 1960 emp02 Aster 3000 2305 emp04 Rahel 1500 1227.5 • Sample Run of the program

  24. …Example: Array of Structures #include<iostream.h> #include<conio.h> const int max=20; struct student { int id; char name[20]; int age; }; student stud[max]; int n; void getStudent(); void printStudent(); void main() { getStudent(); printStudent(); getch(); }

  25. … Cont’d void getStudent() { n=0; char ans; do{ cout<<"\n Enter id of the student: "; cin>>stud[n].id; cout<<"\n Enter name of the student: "; cin>>stud[n].name; cout<<"\n Enter age of the student: "; cin>>stud[n].age; n++; cout<<"\n Any more student?y/n: "; cin>>ans; }while(ans=='y' || ans=='Y'); } void printStudent() { cout<<"\n Student Info\n\n"; cout<<"\n ID\t Name \t Age \n"; for(inti=0; i<n; i++) cout<<stud[i].id<<"\t"<<stud[i].name<<"\t"<<stud[i].age<<endl; }

  26. Cont’d… • Sample run of the program Enter id of the student: 11 Enter name of the student: Bekele Enter age of the student: 21 Any more student?y/n: y Enter id of the student: 33 Enter name of the student: Aster Enter age of the student: 23 Any more student?y/n: n Student Info ID Name Age 11 Bekele 21 33 Aster 23

  27. Nested Structures struct date { int day; int month; int year; }; struct employee { char empID[5]; char name[20]; date dob; //date of birth float salary; }; • Structures within another structures are called nested structures structaddressInfo { charsubcity[20]; charworeda[20]; charkebele[2]; }; struct employee { charempID[5]; char name[20]; addressInfoaddress; float salary; }; Nested structure Nested Structure

  28. Nested Structure #include<iostream.h> #include<conio.h> const int max=20; struct date { int day; int month; int year; }; struct employee { char empID[10]; char name[20]; date dob; //date of birth float salary; }; employee emp[max]; int n;

  29. Cont’d… void getEmployee() { char ans; n=0; do{ cout<<"\n Enter id of the employee: "; cin>>emp[n].empID; cout<<"\n Enter name of the employee: "; cin>>emp[n].name; cout<<"\n Enter birth date of the employee"; cout<<"\n Day: "; cin>>emp[n].dob.day; cout<<"\n Month: "; cin>>emp[n].dob.month; cout<<"\n Year: "; cin>>emp[n].dob.year; cout<<"\n Enter salary of the employee: "; cin>>emp[n].salary; n++; cout<<"\n Any more employee?y/n: "; cin>>ans; }while(ans=='y' || ans=='Y'); }

  30. Cont’d… void printEmployee() { cout<<"\n Employee Info\n\n"; cout<<"\n ID\t Name\t Date of birth\t Salary \n"; for(inti=0; i<n; i++) cout<<emp[i].empID<<"\t"<<emp[i].name<<"\t"<<emp[i].dob.day<<'/'<<emp[i].dob.month<<'/'<<emp[i].dob.year<<"\t"<<emp[i].salary<<endl; } void main() { getEmployee(); printEmployee(); getch(); }

  31. Cont’d… (Sample Run of the program) Enter id of the employee: emp01 Enter name of the employee: Abdul Enter birth date of the employee Day: 16 Month: 5 Year: 1998 Enter salary of the employee: 2500 Any more employee?y/n: y Enter id of the employee: emp02 Enter name of the employee: Dawit Enter birth date of the employee Day: 8 Month: 8 Year: 1994 Enter salary of the employee: 1500 Any more employee?y/n: n Employee Info ID Name Date of birth Salary emp01 Abdul 16/5/1998 2500 emp02 Dawit 8/8/1994 1500

  32. Demonstration for Assignment • In groups of 3 or 4 members write a program satisfying the following requirements:

  33. Assignment (Final Project part one) • Write a menu driven program using structures of inventory items that consists of a minimum of the following functionalities: • getItem… to input inventory data • searchItem… to search inventory item • displayItem…. To display inventory items • The displayItem function should display item code, item name, item quantity and total price of a given item • The inventory structure should have the following minimum fields: itemCode (string), itemName (string), quantity (int), unitPrice(float)

  34. Next topic • Data File Operations

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