10: Information Hiding
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Questions and Answers

What is the main purpose of information hiding in programming?

  • To improve the performance of the code
  • To expose all details of a data structure
  • To only allow private access to data members
  • To separate declarations from definitions (correct)

The header file should include both declarations and definitions of functions.

False (B)

What is the purpose of the operator+ function in the rational struct?

To return the sum of two rational numbers.

In a rational struct, the variable 'd' must not equal ___ to maintain its invariant.

<p>0</p> Signup and view all the answers

Match the following components of the rational struct with their descriptions:

<p>int n = Numerator of the rational number int d = Denominator of the rational number operator+ = Function for adding two rationals operator- = Function for subtracting two rationals</p> Signup and view all the answers

What does the 'struct rational' primarily represent?

<p>An object that holds pairs of integers representing a fraction (B)</p> Signup and view all the answers

Encapsulation ensures that users understand how functions within a struct are implemented.

<p>False (B)</p> Signup and view all the answers

What is a requirement for a rational number to be stored in a reduced form?

<p>The numerator and denominator must have no common factors other than 1.</p> Signup and view all the answers

The term ___ describes a programming technique to prevent users from accessing and modifying internal states directly.

<p>encapsulation</p> Signup and view all the answers

Which part of the struct declaration ensures that the denominator is never zero?

<p>The invariant comment (C)</p> Signup and view all the answers

What does the function v.size() do in relation to vectors?

<p>Returns the number of elements in the vector (D)</p> Signup and view all the answers

In C++, by default, all members of a class are public.

<p>False (B)</p> Signup and view all the answers

What is the primary purpose of encapsulation in C++?

<p>To hide the internal representation and expose only functionality.</p> Signup and view all the answers

In the example provided, the class 'rational' uses two private members: an integer 'n' and an integer '____'.

<p>d</p> Signup and view all the answers

Match the following C++ access modifiers with their visibility type:

<p>public = Accessible from anywhere private = Accessible only within the class protected = Accessible in derived classes default for struct = Accessible from anywhere</p> Signup and view all the answers

Which of the following statements is true regarding the differences between structs and classes in C++?

<p>Both structs and classes can have private members (C)</p> Signup and view all the answers

The internal representation of an object in a class should be visible to the user.

<p>False (B)</p> Signup and view all the answers

What is one way to change the internal representation of a class without affecting user code?

<p>By changing the representation of data types (e.g., polar to Cartesian coordinates).</p> Signup and view all the answers

The principle of information hiding can be implemented in C++ using ____.

<p>classes</p> Signup and view all the answers

Match the following terms with their definitions:

<p>Encapsulation = Hiding the internal state of an object Public = Members accessible from anywhere Private = Members only accessible within the class Struct = A variant of class with default public access</p> Signup and view all the answers

What is the purpose of member functions in a class?

<p>They allow access to private data members. (A)</p> Signup and view all the answers

Private members of a class can be accessed from outside the class directly.

<p>False (B)</p> Signup and view all the answers

What must be checked before setting the denominator in the example provided?

<p>The denominator value must not be zero.</p> Signup and view all the answers

The __ function allows setting the numerator of a rational instance.

<p>set_numerator</p> Signup and view all the answers

Match the following member functions with their descriptions:

<p>numerator = Returns the numerator of the instance set_numerator = Sets the numerator of the instance denominator = Returns the denominator of the instance set_denominator = Sets the denominator of the instance to a value and checks for zero</p> Signup and view all the answers

Which of the following statements about class member functions is true?

<p>They can access both public and private data members. (B)</p> Signup and view all the answers

In object-oriented programming, hiding data does not serve any useful purpose.

<p>False (B)</p> Signup and view all the answers

What is a common misconception about information hiding in programming?

<p>That it limits access to useful data.</p> Signup and view all the answers

The class definition implies that 'd' must always be _____ while being set.

<p>non-zero</p> Signup and view all the answers

How can an instance of the class rational access member functions?

<p>Using dot notation. (B)</p> Signup and view all the answers

What is the purpose of the const keyword in member function declarations?

<p>To ensure the member function cannot change the instance's state (D)</p> Signup and view all the answers

The denominator of a rational number can be zero.

<p>False (B)</p> Signup and view all the answers

What is the implicit parameter called that is accessible within member functions?

<p>this</p> Signup and view all the answers

In the member function declaration, _____ is used to prevent the modification of the instance.

<p>const</p> Signup and view all the answers

What will happen if a const object attempts to call a non-const member function?

<p>An error will occur (D)</p> Signup and view all the answers

In a rational number, setting the numerator can always result in an error.

<p>False (B)</p> Signup and view all the answers

What is the significance of the member function 'numerator()' in the rational class?

<p>It returns the value of the numerator.</p> Signup and view all the answers

When a member function is called, the expression with a value of class type is passed implicitly as _____ to the function.

<p>this</p> Signup and view all the answers

What does the statement 'int n = y.numerator();' demonstrate?

<p>Accessing the numerator of a const object (A)</p> Signup and view all the answers

In C++, a class by default has all its members as private.

<p>False (B)</p> Signup and view all the answers

What is enforced by the invariant in the rational struct?

<p>The denominator 'd' must not equal zero.</p> Signup and view all the answers

In C++, the keyword _____ is used to indicate a member function that does not modify the object.

<p>const</p> Signup and view all the answers

Match the following C++ keywords with their descriptions:

<p>class = Defines a data type with methods and properties struct = Defines a simple data structure, usually with public members private = Specifies that class members are not accessible from outside the class public = Specifies that class members are accessible from outside the class</p> Signup and view all the answers

Which of the following statements is true about the member function 'numerator()' in the rational class?

<p>It returns the value of the numerator. (A)</p> Signup and view all the answers

An object of class rational can directly access its member variables without a member function.

<p>False (B)</p> Signup and view all the answers

What does the struct rational contain as its members?

<p>Two integers: n (numerator) and d (denominator).</p> Signup and view all the answers

What is the default access modifier for members of a class in C++?

<p>Private (C)</p> Signup and view all the answers

In C++, struct members are private by default.

<p>False (B)</p> Signup and view all the answers

What keyword is used to declare a member function that does not modify the object?

<p>const</p> Signup and view all the answers

To access private members of a class from outside, you must use _____ members.

<p>public</p> Signup and view all the answers

Match the access modifiers with their visibility:

<p>Public = Accessible from anywhere Private = Accessible only within the class Protected = Accessible within the class and its subclasses Internal = Accessible within the same package</p> Signup and view all the answers

Which function call would give access to a private member from outside the class?

<p>obj.memberFunction() (D)</p> Signup and view all the answers

Member functions can only be defined inside the class definition.

<p>False (B)</p> Signup and view all the answers

The keyword _____ is used to ensure that functions in a class can only access their own members.

<p>this</p> Signup and view all the answers

Which of the following statements is true regarding member functions?

<p>They can directly access private members of the class. (B)</p> Signup and view all the answers

Flashcards

Information Hiding

A technique used to hide the internal details of a data structure or function from the user, allowing for cleaner code and easier maintenance.

Encapsulation

A mechanism that combines data and functions that act on that data into a single unit, encapsulating the internal details.

Invariants

Rules or conditions that must always be true for a data structure to remain consistent.

Representation

The internal structure and implementation of a data structure.

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Rational Struct

A data structure that represents a rational number, consisting of a numerator and a denominator.

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Header file

A file that contains only declarations of functions, structs, or classes. It provides an interface for users.

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Implementation file

A file that contains the definitions of functions, structs, or classes declared in a header file.

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Operator Overloading

A type of function that allows for the use of operators like '+' or '-' on user-defined data structures.

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Separation of Interface and Implementation

The practice of separating the interface of a library or module from its implementation, allowing for modularity and maintainability.

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Enum

A type of data structure that is used to represent a limited range of values, often used for representing boolean values (true/false), characters, or small integers.

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What is a member function?

A member function is a function that belongs to a class. It has access to the private data members of the class.

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Why use member functions?

Member functions are used to access and modify private data members of a class. This allows controlled access to the internal state of an object.

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How do you call a member function?

Member functions are called using the dot operator (.) on an object of the class. For example, object.member_function().

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What does the const keyword do for member functions?

Member functions can be declared as const to ensure they do not modify the object's state. This enhances object immutability and data integrity.

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How can you tell if a member function is meant to be constant?

The const keyword after a member function's declaration indicates that the function cannot modify the object's data members.

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What is the significance of member functions for data encapsulation?

Member functions are crucial for encapsulating data and ensuring proper data handling within a class.

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What privilege do member functions have?

Member functions have access to the private data members of the class, allowing them to perform operations on that data.

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What purpose does the assert statement serve in member functions?

The assert statement is used to check preconditions, ensuring that the function receives valid input before executing.

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What are invariants in the context of member functions?

Invariants define rules that must always hold true for the internal state of a class. Member functions, particularly those that modify data, should preserve these invariants.

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How do member functions contribute to data hiding?

Member functions promote data hiding, controlled access, and ensure that data can only be modified through defined methods.

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Const Member Function

A member function declared with the const keyword ensures that the function cannot modify the object it is called on. It guarantees that the object's internal state remains unchanged during the function's execution.

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Implicit this Parameter

When a member function is called, the object it is called on is implicitly passed as a hidden argument, referenced as this. This allows the function to access the object's data and members.

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Const Restriction on this Pointer

The const keyword in a member function declaration restricts the function's ability to modify the object through the implicit this pointer.

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Const Member Function Guarantees

The const keyword in a member function declaration guarantees that the function cannot modify the object's members or data.

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Const Objects & Const Member Functions

Const objects can only call const member functions, ensuring that their data remains untouched.

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Member Function Access Using this Pointer

The this pointer in a member function provides access to the object's data and members.

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Using const in Member Function Declarations

In a class, the keyword const is used before a member function declaration to indicate that the function will not modify the object it is called on.

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Implicit this Pointer in Member Functions

The this pointer acts as a hidden, implicit parameter that allows member functions to access the object's data and members.

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Direct Access to Object Data Using this Pointer

The this pointer in member functions allows for direct access to the object's data, as in this->n.

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Member Functions: Methods for Objects

Member functions act like methods specific to an object, providing a way to interact with and manipulate its data and behavior.

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String in C++

A type of data structure in C++ that allows you to store and manipulate sequences of characters. It provides functions like size(), [], and push_back() for accessing and modifying the contents of the string.

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Class in C++

A data structure in C++ that groups data members and member functions together. It encapsulates data and provides a controlled way to access and modify it.

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Public and Private Access Specifiers in C++

A specifier used in C++ to control the accessibility of data members and member functions within a class. Public members can be accessed from anywhere. Private members are accessible only within the class definition.

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Inheritance in C++

A mechanism in C++ that enables code reuse by allowing classes to inherit properties and methods from other classes.

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Rational Class in C++

A class in C++ designed specifically for representing fractions with a numerator and a denominator.

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Invariant in C++

A constraint or rule that must be maintained for a class to function correctly. It defines the acceptable state of the class and its data members.

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Abstraction in C++

A concept in C++ that emphasizes separating the interface of a class or data structure from its implementation. It allows users to interact with the class without needing to know how it works internally.

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Class vs. Struct in C++

A specialized kind of class in C++ that combines the encapsulation features of a class with the default public accessibility of a struct. It allows you to control the accessibility of members with keywords like public, private, and protected.

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Representation in C++

A value or state in C++ that can be used to represent different values of a data type.

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C++ String

A C++ data structure that allows you to store and manipulate sequences of characters. Think of it as a way to represent text in your program.

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Class

A blueprint or template for creating objects in C++. It defines the data (variables) and functions (methods) that an object of that class will have.

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Constructors

Special functions within a class that are automatically called when an object of that class is created. They help initialize the object's data with default values.

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Member Functions

Functions defined inside a class that can access and modify the private data members of the class. They define the behavior of objects of that class.

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Rational

A data structure that represents a rational number as a fraction with a numerator and a denominator. It's like a mathematical fraction stored in your program.

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Member Function Access with this

The this pointer is used within member functions to access the object's data and members directly.

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Public and Private Access Specifiers

Public members of a class can be accessed from anywhere, while private members are accessible only within the class definition. Public members are the interface, while private members are hidden implementation details.

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Study Notes

Introduction to Computer Science Course Information

  • Course code: 252-0032, 252-0047, 252-0058
  • Authors: Manuela Fischer and Felix Friedrich
  • Department: Computer Science, ETH Zurich
  • Semester: Fall 2024

Information Hiding

  • A new type, like rational, is stored in a library.
  • Declaration and definition distinctions are made.
  • A header file (rational.h) holds declarations (Code 13.1).
  • An implementation file (rational.cpp) holds definitions (Code 13.2).

Encapsulation

  • Invariants need to be defended, i.e. rational.d != 0.
  • Users should be given the what not the how.
  • The internal representation can be changed without rewriting user code (e.g., polar to Cartesian coordinates).
  • A type is defined by its values and functionality, but representation is hidden.
  • Functionality is important, not the representation.
  • Encapsulation is offered in C++ via classes.

Classes

  • Classes use encapsulation in C++.
  • A struct's members are public by default.
  • Class members are private by default in C++.
  • Public members can be accessed outside the class.
  • Private members cannot be accessed outside the class.

Member Functions

  • Member functions can access private data.
  • Member functions can be public.
  • Accessing members happens using the syntax r.member_function().
  • const after a member function assures the object won't be changed.
  • Example: rational x; x.set_numberator(); const rational y = x; y.numerator();
  • Member functions can be declared in-class or out-of-class (Code 13.14, 13.15 and 13.16, separate declaration and definition files for classes can be used). Scope resolution (::) is required when defining a member function outside its class.

Constructors

  • Constructors are special member functions with the same name as the class.
  • They initialize class members.
  • They can be overloaded with different parameters.
  • If no constructor is provided, a default one is created. A default constructor initializes member variables using their default initialization values.
  • The assert(d != 0) is a critical check in the constructor to guarantee the invariant.
  • Default constructors can be deleted to prevent implicit creation (Code 13.7).

User-Defined Conversions

  • Converting from int to rational is allowed using a constructor, e.g., rational r = rational(2)
  • Implicit conversions are also possible, like rational s = 2.
  • Conversions to other types (e.g., double) can be defined using conversion operators (Code 13.9).

Containers and Iterators

  • Data structures for storing collections are called containers.

  • Containers: like std::vector, std::list, std::unordered_set, std::set are provided with associated iterators (like std::vector<int>::iterator). These iterators let one traverse container elements.

  • std::vector: Efficient index-based access; but inserting at/removing from arbitrary indices is potentially slower. It can contain the same element multiple times.

  • std::list: Efficient insertion and removal, but not index-based access and slower lookups. Similar to vectors, elements are in insertion order, but not sorted.

  • std::unordered_set: Efficient “element contained?” checks and insertion and removal. Elements do not maintain a specific order.

  • std::set: Elements are in order; slower insertions than std::unordered_set

Iterators

  • Used to iterate over containers efficiently.
  • The use of iterators decouples iterating over the container from how the container stores its data.
  • Can modify elements within the container (mutating iterators) or only access and use them (constant iterators). Example for (auto it = v.begin(); it!=v.end(); ++it) will traverse the container v. The examples neg(v.begin(), v.begin() + (v.size() / 2)); demonstrate functional approach.

Const Iterators

  • Guarantee read-only access to the container.
  • Necessary for accessing elements of a constant container (e.g const vector<int> v). Use v.cbegin() and v.cend() to get constant iterators.

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Related Documents

Introduction to Computer Science PDF Fall 2024
C++ Information Hiding & Classes Lecture Notes PDF
Programmierbefehle - Woche 10 PDF

Description

This quiz covers key concepts from the Introduction to Computer Science course, focusing on information hiding and encapsulation in C++. It explores the distinctions between declaration and definition, the purpose of header and implementation files, and the principles of encapsulation through classes in C++. Test your understanding of these foundational topics!

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