Chapter 11 - Abstract data types

Question 1

what is an abstraction?

Answer 1

a view or representation of an entity that includes only the most significant attributes

Question 2

what is an abstract data type?

Answer 2

• a data representation of one specific data type

- the subprograms that provide the operations for that type

Question 3

6 Design issues for abstract data types

Answer 3

• what is the form of the container
• what types can be abstract
• can abstract types be parameterized
• what access controls are provided
• is the specification of the type physically separate from its implementation
• should general built-in operations be provided from objects of abstract data types

Question 4

What is an object

Answer 4

an instance of an abstract data type

Question 5

What is the encapsulation construct in Ada

Answer 5

the package

Question 6

4 characteristics of C++ class

Answer 6

• an encapsulation device
• all class instances share a single copy of the member functions
• each instance of a class has its own copy of the class data members
• instances can be static, stack dynamic, or heap dynamic

Question 7

6 characteristics of C++ constructors

Answer 7

• they initialize objects
• may allocate storage for any parts that are heap-dynamic
• can include parameters to provide parameterization of the objects
• implicitly called when an instance is created
• can be explicitly called
• name the same as class

Question 8

5 characteristics of C++ destructors

Answer 8

• implicitly called when the lifetime of an instance of the class ends
• often used for delete of heap-dynamic data allocated within the class
• often used for debugging or statistical analysis
• can be explicitly called
• the name is ~class_name

Question 9

3 differences of Java objects than C++ objects

Answer 9

• all objects are allocated on the heap and accessed through reference variables
• individual entities in classes have access modifiers (public, private) rather than clauses
• has an extra scoping mechanism “package scope” to be used in place of friends

Question 10

3 characteristics of abstract data types in C#

Answer 10

• all class instances are heap dynamic
• default constructors are predefined for all classes
• C# allows destructors but it uses garbage collection so they are rarely used

Question 11

6 characteristics of C# structs

Answer 11

• they can have constructors, properties, methods, and data fields
• can implement interfaces but do not support inheritance
• they are value types (their data is allocated to memory on the stack)
• they default to pass by value when used as parameters
• they can be declared like other types
• they can also be created using new operator with invokes the constructor

Question 12

3 characteristics of Ruby classes (that I probably don’t know)

Answer 12

class methods are distinguished from instance methods by having a class name appended to the beginning of their names with a dot separator

constructors are called “initialize”

classes can be “updated” any place in the text

Question 13

Ruby undef_method vs remove_method

Answer 13

undef_method - blocks any reference to a given method

remove_method - block deletes method from class but allows those class objects to look for method definition in parent

Question 14

4 characteristics of information hiding in Ruby

Answer 14

• access control violations are only detected at runtime
• uses public (default), protected, and private
• all data members of a class are private and cannot be changed
• data access is via methods only

Question 15

what is an encapsulation construct?

Answer 15

-a way of organizing programs into collections of logically related code and data, each of which can be compiled without recompilation of the rest of the program

Question 16

Examples of encapsulation constructs in C, C++, Ada, C#

Answer 16

C –> header and implementation files

C++ –> header/implementation and class header/implemenatation files

Ada –> packages (can include any number of interfaces to ADTs)

C# –> assemblies (mimics a dll or exe)

Question 17

why use named encapsulations?

Answer 17

when dealing with large programs written by many coders working independently named encapsulations define scopes that help avoid name collisions/duplication

Question 18

4 examples of named encapsulation?

Answer 18

C++ namespace

Java package

Ada package

Ruby modules

Question 19

5 characteristics of Java packages

Answer 19

• may contain multiple type definitions
• all types in the package are partial friends
• package declaration must be the first line of the file
• all types outside of a package are part of the default unnamed Java package
• access similar to C++ (add using import blah)

Question 20

2 things for using Ada package data

Answer 20

• visibility to the package is gained by using “with” clause
• member references must be qualified “Ada.pkg_name.method or use the “use” clause

use Ada.pkg_name
method…

Question 21

6 characteristics of Ruby modules

Answer 21

• may contain methods and constants
• cannot define variables
• cannot be instantiated
• cannot be inherited
• a method defined in a module must include the module name
• clients access module first by “require” then by module name