Understanding Records in C++: A Guide to Structs and Their Operations

1. CHAPTER 12RECORDS (Structs)

2. In this chapter, you will: • Learn about records (structs) • 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 of struct items

3. Records (Struct) • struct: A collection of fixed number of components in which components are accessed by name is called a struct. The components may be of different types. struct employeeType { string firstName; string lastName; string address1; string address2; double salary; string deptID; }; • struct is a definition not a declaration. No memory is allocated. • Memory is allocated when we declare variables.

4. struct studentType { string firstName, lastName; char courseGrade; int testScore, programmingScore; double GPA; }; studentType newStudent; //variable declaration studentType student;

5. Accessing structMembers In C++, the . (dot) is an operator, called the member access operator. newstudent.gpa = 0.0; newStudent.firstName = "John"; newStudent.lastName = "Brown"; cout << newStudent.firstName;

6. Assignment We can assign the value of one struct variable to another struct variable of the same type using an assignment statement.

7. student = newstudent;

8. student = newstudent; This statement 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;

9. Comparison • struct variables must be compared member-wise. • To compare the values of student and newStudent, you must compare them member-wise, as follows: if(student.firstName == newStudent.firstName && student.lastName == newStudent.lastName) . . .

10. Input/Output • There are no aggregate input/output operations on struct. • Data in a struct variable must be read one member at a time. • Contents of a struct must be written one member at a time. The statement cout<<newStudent.firstName<<" " <<newStudent.lastName<<" " <<newStudent.courseGrade<<" " <<newStudent.testScore<<" " <<newStudent.programmingScore<<" " <<newStudent.GPA<<endl; outputs the content of the struct variable newstudent.

11. struct Variables and Functions • A struct variable can be passed as a parameter either by value or by reference. • A function can return a value of the type struct.

12. void readIn(studentType& student) { int score; cin>>student.firstName>>student.lastName; cin>>student.testScore>>student.programmingScore; cin>>student.GPA; score = newStudent.testScore + newStudent.programmingScore; if(score >= 90) student.courseGrade = 'A'; else if(score >= 80) student.courseGrade = 'B'; else if(score >= 70) student.courseGrade = 'C'; else if(score >= 60) student.courseGrade = 'D'; else student.courseGrade = 'F'; }

13. The statement readIn(newStudent); calls the function readIn. • The function readIn stores the appropriate information in the variable newStudent.

14. void printStudent(studentType student) { cout<<student.firstName<<" " <<student.lastName<<" " <<student.courseGrade<<" " <<student.testScore<<" " <<student.programmingScore<<" " <<student.GPA<<endl; }

16. Arrays in Structs const arraySize = 1000; struct listType { int elements[arraySize]; //array containing the list int listLength; //length of the list }; int seqSearch(const listType& list, int searchItem) { int loc; boolfound = false; for(loc = 0; loc < list.listLength; loc++) if(list.elements[loc] == searchItem) { found = true; break; } if(found) return loc; else return –1; }

17. Structs in Arrays • Suppose there are 50 full time employees in a company. • Print their monthly pay check and also keep track of how much money has been paid year to date. • Define an employee’s record. struct employeeType { string firstName; string lastName; int personID; string deptID; double yearlySalary; double monthlySalary double yearToDatePaid; double monthlyBonus; };

18. employeeType employees[50];

19. The following C++ code loads the data into the employees’ array. • We assume that initially yearToDatePaid is 0 and that the monthly bonus is determined each month based on performance. ifstream infile; //input stream variable assume //that employee.dat file has been opened for(counter = 0; counter < 50; counter++) { infile>>employees[counter].firstName >>employees[counter].lastName >>employees[counter].SSN >>employees[counter].deptID >>employees[counter].yearlySalary; employees[counter].monthlySalary = employees[counter].yearlySalary/12; employees[counter].yearToDatePaid = 0.0; employees[counter].monthlyBonus = 0.0; }

20. double payCheck;//variable to calculate the paycheck for(counter = 0; counter < 50; counter++) { cout<<employees[counter].firstName<<" " <<employees[counter].lastName<<" "; payCheck = employees[counter].monthlySalary + employees[counter].monthlyBonus; employees[counter].yearToDatePaid = employees[counter].yearToDatePaid + payCheck; cout<<setprecision(2)<<payCheck<<endl; }

21. Structs within a struct struct employeeType { string firstname, middlename, lastname; string emplID; string address1, address2; string city; string state; string zip; string hiremonth, hireday, hireyear; string quitmonth, quitday, quityear; string phone; string cellphone; string fax; string pager; string email; string deptID; double salary; };

22. struct dateType { string month; string day; string year; }; struct contactType { string phone; string cellphone; string fax; string pager; string email; }; struct nameType { string firstname; string middlename; string lastname; }; struct addressType { string address1; string address2; string city; string state; string zip; };

23. struct employeeType { nameType name; string emplID; addressType address; dateType hiredate; dateType quitdate; contactType contact; string deptID; double salary; }; // variable declaration employeeType newEmployee; employeeType employees[100];

24. newEmployee.salary = 45678.00; newEmployee.name.first = "Mary"; newEmployee.name.middle = "Beth"; newEmployee.name.last = "Simmons"; cin>>newEmployee.name.first; newEmployee.salary = newEmployee.salary * 1.05; for(j = 0; j < 100; j++) cin>>employees[j].name.first >>employees[j].name.middle >>employees[j].name.last;