Basic C Programming

1
Basic C Programming
Review C Programming Elements, Expressions,
Control Flow, Functions, Classes
2
Classes ( 1.5)

• The concept of a class is fundamental to C
• provides means to define new user-defined types
• may have associated functions and operators
• fundamental to programming using the
  object-oriented approach
• often used to implement data structures (a
  systematic way of organizing and accessing data)

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Class Structure ( 1.5.1)

• A class consists of members
• properties
• data members
• constants or variables
• may be of any type, even classes
• methods
• member functions
• typically act on the properties, so define the
  behavior of the class

4
Access Control ( 1.5.1)

• Members may be declared either public, private,
  protected, or friend (using access specifiers)
• public
• accessible from within and outside the class (by
  client code)
• the public interface of the class object
• private
• accessible only from within the class
• usually properties are made private, as they deal
  with how the data structure is implemented (users
  dont need to know)

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Class Syntax ( 1.5.1)

• class class_name
• private
• //private members
• public
• //public members
• Note No required order between public and
  private sections. Usually public section first,
  since of most interest to users. However, our
  authors focus on the structures, so usually list
  the private section first!
• Default access is private for classes and public
  for structures.

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Class Example ( 1.6.1)

• See Code Fragment 1.5, page 48
• class CreditCard
• private
• string number //cc number
• string name //cc owner's name
• int limit //credit limit
• double balance //cc balance
• public
• //constructor
• CreditCard(string no, string nm, int lim,
  double bal0)
• //accessor functions
• string getNumber() const return number
• string getName() const return name
• double getBalance() const return balance
• int getLimit() const return limit
• //mutator functions
• bool chargeIt(double price)

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Member Functions ( 1.5.1 1.6.1)

• class CreditCard
• private
• //..
• public
• //constructor
• CreditCard(string no, string nm, int lim,
  double bal0)
• //..
• Constructor
• initializes the class properties
• has the same name as the class itself
• does not have a return type

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Member Functions ( 1.5.1 1.6.1)

• Other member functions are categorized as
• accessor functionsonly read class data
• class CreditCard
• private
• //..
• public
• //..
• //accessor functions
• string getNumber() const return number
• string getName() const return name
• //..
• Note the const declaration indicates
  getNumber(), etc. are all accessor
  functionsinforms user that function will not
  modify the object properties

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Member Functions ( 1.5.1 1.6.1)

• Other member functions are categorized as
• accessor functionsonly read class data
• mutator/update functionsmay alter class data
• class CreditCard
• private
• //..
• public
• //..
• //mutator functions
• bool chargeIt(double price)
• void makePayment(double payment)
• balance - payment

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Member Functions ( 1.5.1 1.6.1)

• May either be defined within the class body or
  outside.
• class CreditCard
• private
• //..
• public
• //..
• //mutator functions
• //defined outside
• bool chargeIt(double price)
• //defined here
• void makePayment(double payment)
• balance - payment

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Defined Within ( 1.5.1 1.6.1)

• We give a hint to the compiler to expand this
  function in-linesimply expand the contents of
  the function body each time it is encountered,
  rather than using the usual call-return method.
• //defined here
• void makePayment(double payment)
• balance - payment
• Thus, in-line functions can be executed more
  efficiently. Use for frequently-used, short
  member functions.

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Defined Outside ( 1.5.1 1.6.1)

• Required to specify both the name of the class as
  well as the function name (so compiler knows
  which class is involved). See Code Fragment 1.6,
  page 49.
• bool CreditCardchargeIt(double price)
• //make a charge
• if(price balance gt double(limit)) return
  false
• balance price
• return true

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Using Member Functions ( 1.5.1 1.6.1)

• Note that member names, like chargeIt(), are used
  without reference to a particular objectthese
  functions will be invoked on a particular object.
  See Code Fragment 1.7, page 50.
• vectorltCreditCardgt wallet(10)//vector of 10
  CreditCard //pointers
• //allocate a new card
• wallet0 new CreditCard("5391 0375 9387
  5309", "John Bowman", 2500)
• //..
• for(int j1 jlt16 j)
• //make some charges
• wallet0-gtchargeIt(double(j))
• //..
• Since wallet0 is a pointer to a CreditCard, use
  -gt to invoke the member function chargeIt()
  (otherwise if not a pointer type use . ).

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Constructors Destructors ( 1.5.2 1.6.1)

• Constructors
• special member functions
• initialize the class properties
• have the same name as the class itself
• do not have a return type
• Destructors
• called when a class object goes out of existence
• if class name is T, denoted T()

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Constructors ( 1.5.2 1.6.1)

• Special constructors are
• default constructors
• no arguments
• copy constructors
• Note our example
• class CreditCard
• public
• //constructor
• CreditCard(string no, string nm, int lim, double
  bal0)
• contains a default argument, bal. If a
  CreditCard object is instantiated with only two
  arguments, then bal will be set to 0.
• Default arguments may be used with any function
  (not just constructors.)

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Destructors ( 1.5.2)

• a member function automatically called when a
  class object ceases to exist
• if class name is T, denoted T()
• not required to supply our own
• if our class allocates memory via new, we should
  write a destructor to free its memory via delete
  (or introduce memory leaks)

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Classes Memory Allocation ( 1.5.3)

• Every class that allocates its own objects using
  new should
• Define a destructor to free allocated objects
• Define a copy constructor, which allocates its
  own new member storage and copies the contents of
  member variables
• Define an assignment operator, which deallocates
  old storage, allocates new storage, and copies
  all member variables
• Read this section for more details.

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Class Friends and Class Members( 1.5.4)

• Well come back to this.

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The Standard Template Library ( 1.5.5)

• The STL is a collection of useful classes for
  common data structures/standard containers
• string
• stack
• queue
• deque
• vector
• list
• priority-queue
• set
• map

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The Standard Template Library ( 1.5.5)

• Each object can store objects of any type.
• Such a class whose definition depends on a
  user-defined type is called a template.
• Specify the type of object being stored in angled
  brackets lt..gt
• vectorltintgt scores(100)//100 integer scores
• vectorltCreditCardgt wallet(10)//vector of 10
  CreditCard //pointers
• Read this section for further details