constructs

Question 1

what is a procedure?

Answer 1

• way of grouping code together to form an abstraction

* can be used again and again and bugs found only require fixing once

Question 2

behavior of a procedure - 3

Answer 2

• operates on its data (data is not abstract)
• specified via its declaration (aka prototype/signature)
• any data representations are usable throughout the program

Question 3

what is a module?

Answer 3

• collection of procedures and variables
• allows procedures to share hidden data
• provide a public (interface) and private (implementation) view

Question 4

Pascal supports

Answer 4

• supports procedures and variables within procedures

* a collection of procedures cannot share hidden data

Question 5

C supports

Answer 5

• limited support for modules (mimics modules with keyword “static” inside a file)
• uses name equivalence for structs (actual structure definition is placed in the same file…aka module)

Question 6

type abstraction through modules - 3

Answer 6

• done through limited or opaque types
• representation of a type is kept hidden
• most implementations of true modules provide type as well as procedural abstractions

Question 7

limited type (modules) - 4

Answer 7

• implementation visible only to module
• name of type visible to client
• name equivalence must be used (not structural)
• usually done as pointer types (size of a pointer is generally the same regardless of object being pointed to)

Question 8

limited types in C

Answer 8

done through opaque pointer types

Question 9

opaque pointer types

Answer 9

a pointer to an incomplete type

Question 10

limitation of C’s type abstraction

Answer 10

objects created obey pointer semantics

• need explicit initializer (constructor)
• need explicit de-initialize (destructor)
• assignment copies pointer, not the object

Question 11

what is a class? - 5

Answer 11

• corresponds to a type
• same abilities as built-in types
• should be first class
• supports information hiding (public and private components)
• abbr. for “class of objects”

Question 12

classes vs. objects

Answer 12

• objects are concrete; classes are abstract

* operations performed on objects only (not on classes)

Question 13

what is an object?

Answer 13

an object is an instance of a class

Question 14

what is a struct?

Answer 14

a class in which all members are public by default

Question 15

classes in C++

Answer 15

• generalization of structures
• simply a struct in which all members are private by default
• can contain data and functions (only data in C)

Question 16

interface vs. implementation locations (class)

Answer 16

• interface should be in a header file
• implementation should be in a separate source file
• client only needs header file and compiled source file

Question 17

inlining

Answer 17

• C++ allows function bodies (implementation) in header files so that the body of the function can be expanded at the point of its call
• ideally the compiler does this for you (don’t put function bodies in header unless very short)

Question 18

what are member functions (C++) or methods (rest of OO world)?

Answer 18

• functions within a class in C++
• two special member functions
  1) constructors
  2) destructors

Question 19

what is a constructor?

Answer 19

• named after the class, has no return type
• job: initialize members of the class
• implicitly called when an object is declared

Question 20

what is a destructor?

Answer 20

• each class can have one
• has the same name as the class preceded by a tilde
• job: release resources allocated or in use by the object
• always called implicitly

Question 21

what is a resource?

Answer 21

• anything the object has created, been allocated or has in use