How does the OS control system resources?

Classes

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  Structs group together related data of various types into a single user type (eg: employee struct may include: name, age etc.)
  
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  We can construct an ADT by associating various functions with the data to perform different tasks such as manipulation, initialisation, retrieval. However the major disadvantage of this is a lack of security & control:
  
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    ie: it is easy to write code to manipulate the employee ADT data without using the associated functions (eg: employee.age = age - 100)
    
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  The notion of encapsulating operations & data is embodied in C++ as classes, which group together data & code into a single user type.
  

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  eg:
  

  // employeeclass.h (class header file) #ifndef EMPLOYEE_H #define EMPLOYEE_H #include "apstring.h" class employeeClass { public: void initEmployee(); // default value initialisations void readEmployee(); // user input initialisations void printEmployee(); // display data private: apstring name, e-mail; int age; double salary; }; #endif

  // employeeclass.cpp (class implementation file) #include "employee.h" void employeeClass::initEmployee() { name = "John Doe"; e-mail = "joh_doe@doe.com"; age = 21; salary = 10000.00; } void employeeClass::readEmpoyee() { cout << "Enter Name: "; cin.getline(name); cout << "Enter E-mail: "; cin.getline(e-mail); cout << "Enter Age: "; cin >> age; cout << "Enter Salary: $"; cin >> salary; } void employeeClass::printEmployee() { cout << "Name: " << name << endl; cout << "E-mail: " << e-mail << endl; cout << "Age: " << age << endl; cout << "Salary: $" << salary << endl; }

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  note: cin.getline(stringVariable);  is a special function for reading a line of text from the user.
  
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  The effect being that only the operations/functions of the employee ADT have access to the employee data!