Engineering Problem Solving with C

1
Engineering Problem Solving with C

• Fundamental Concepts
• Chapter 8
• Introduction to C

2
The C Programming Language

• A superset of C
• C compilers can be used to compile C programs
• Supports
• Object Oriented Programming (OOP)
• Templates
• Overloading of functions and operators
• Best to think of C as its own language

3
Object Oriented Programming

• Object oriented programming is characterized by
  the use of
• classes
• objects
• inheritance
• polymorphism.

4
Object Oriented Programming

• A class is a programmer defined data type that
  combines data members and function members that
  operate on the data members.
• An object is a variable of a defined class type,
  usually referred to as an instance of a class.

5
Object Oriented Programming

• Inheritance allows a class to inherit attributes
  from an existing class.
• Polymorphism is the ability to assign many
  meanings to the same name.
• Overloading of functions is one example of
  polymorphism in C.

6
Basic C Program Structure
/
Header
Comments
/ global
declarations int main() declarations and
executable statements return 0 //end block of
main
7
First Program

• Comments have two forms in C
• //Single line comments
• /Multi-line comments/
• include files
• ltfilename.hgt //Standard library header file
• myfile.h //Your files (need full path)

8
First Program - sum two numbers
/
Sum two
numbers
/ include
ltiostream.hgt //declares standard I/O library int
main() //must have one and only one function
named main int number1, number2 //declare two
integer variables cout ltlt enter two integers
ltlt endl //prompt for input cin gtgt number1 gtgt
number2 //input values for two variables from
keyboard cout ltlt number1 number2 //output sum
of two numbers to the screen return 0 //end
block of main
9
Simple I/O

• cin
• is an istream object
• streams input from standard input
• uses the gtgt (input operator)
• cout
• is an ostream object
• streams output to standard output
• uses the ltlt (output) operator

10
File Streams

• cin
• object of type istream (an instance of the class
  istream).
• defined for you in file iostream.h
• defined to stream input from standard input
• some associated member functions
• eof()
• get()

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File Streams

• cout
• object of type ostream (an instance of the class
  ostream).
• defined for you in the file iostream.h
• defined to stream output to standard output
• some associated member functions
• put()

12
Programmer Defined File Streams
13
Programmer Defined File Streams
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Programmer Defined File Streams

• To define your own file streams
• for input use ifstream class
• for output use ofstream class
• ifstream and ofstream are defined in file
  fstream.h
• fstream.h also includes istream and ostream class
  

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File Streams

• ifstream is derived from istream
• includes all functions defined for cin - eof(),
  get(), ..
• Includes additional functions not defined for cin
  - open(), close(), fail()

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File Streams

• ofstream is derived from ostream
• includes all functions defined for cout - put(),
  ..
• Includes additional functions not defined for
  cout - open(), close(), fail()

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Defining File Streams

• Include fstream.h
• declare filestream objects
• ifstream fin
• ofstream fout
• use open() to initialize filestreams
• use filestreams just like cin and cout

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Example
include ltfstream.hgt include ltmath.hgt int
main() //Create three columns of data for
plotting. double x ifstream xdata //declare
input stream ofstream plotdata //declare output
stream xdata.open("exp1data" ) //file stream
xdata is now connected to file if( xdata.fail()
) //check for open error cout ltlt "error
opening input file" ltlt endl return 0 //end
if //Continued on next slide.
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plotdata.open("exp1plot) xdata gtgt
x while(!xdata.eof()) if( xgt0 )
//write to plot file plotdata ltlt x ltlt" " ltlt
exp(x) ltlt " " ltltlog(x) ltlt endl //end if
xdata gtgt x //end while xdata.close() plotdata.
close() return 0 //end main
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Introduction to Classes

• The building blocks of object oriented
  programming
• Similar to structures
• Include function members and data members
• A well designed class is as easy to use as a
  pre-defined data type

21
Designing a Class

• Required data members
• Required operations
• Constructor functions
• Accessor functions
• Helper functions
• Friend functions
• Overloaded Operators

22
Writing a Class Definition

• A class definition has two parts
• Class declaration
• Class implementation

23
Class Declaration

• Name of the class is specified using the key word
  class
• Body of the class declaration includes
• declaration statements for the data members
• function prototypes
• Keywords public and private specify the
  accessibility of the class members

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Example - Date Class

• Class Declaration
• class Date
• //class body
• public
• void input(istream)
• void print(ostream)
• void set_data(int, int, int)
• private
• int day, month, year

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Date Class

• Name of the class is Date
• Three private data members
• Three public function members
• Data members can only be accessed by the member
  functions

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Class Implementation

• Includes
• Function definitions for all function members
• Scope Resolution Operator () specifies a
  function as a member of a class

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Implementation of Date Class

• void Dateinput(istream in)
• in gtgt month gtgt day gtgt year
• void Dateprint(ostream out)
• out ltlt month ltlt/ ltltday ltlt / ltlt year
• void Dateset_data(int m, int d, int y)
• month m
• day d
• year y

28
Using Programmer Defined Classes

• Separate Compilation
• Class declaration is saved in a file named
  classname.h
• Class implementation is saved in a file named
  classname.cpp(or whatever extension your compiler
  expects)
• .h file is included in user program and
  implementation file
• User program is linked to implementation file

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Using the Date Class

• include date.h
• int main()
• Date today, birthday
• //member functions are called using the dot
  operator
• today.set(4,6,2000)
• birthday.input(cin)
• today.print(cout)
• birthday.print(cout)
• //how do you determine if today is your birthday?
  

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Operators

• Assignment operator is defined for objects of the
  same type
• Date d1, d2
• d1.input(cin)
• d2 d1
• Other operators are not defined
• arithmetic, relational, logical, input and output

31
Accessor Functions

• Required to access private data members
• Complete set should be provided
• Our Date class requires 3 accessor functions

32
Accessor Function Prototypes

• int get_day()
• int get_month()
• int get_year()

33
Practice!

• 1. Write the function definitions for each of
  the accessor functions for the Date class.

34
Initializing Objects

• Constructor functions are used to initialize
  objects at the time they are declared
• Called automatically
• Same name as the class name
• No return value

35
Constructors for the Date Class

• Default Constructor
• constructor with no arguments
• Prototype
• Date()
• Definition
• DateDate()
• month1
• day1
• year2000

36
Constructors With Parameters

• Prototype
• Date(int, int, int)
• Definition
• DateDate(int m, int d, int y)
• month m
• day d
• year y

37
Overloading Operators

• Allows a programmer defined data type to be used
  as easily as a predefined data type.
• Operators are included in a class definition.
  The keyword operator precedes the name of the
  function.
• The name of the function is one of the predefined
  C operators
• Only predefined operators may be overloaded
• (all operators except . . ? may be
  overloaded)

38
Complex Number Class
A complex number is a number that has two
components the real component and the imaginary
component. a bi Arithmetic on is defined as
follows (a bi) (c di) (a c) (b
d)i (a bi) - (c di) (a - c) (b - d)i (a
bi) (c di) (ac - bd) (ad bc)i (a
bi) / (c di) (ac bd) / (c2d2)
(bc -ad) /(c2d2)i
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Class Declaration
class complex public complex()
void print(ostream) void
input(istream) complex
operator(complex) complex
operator-(complex) complex
operator(complex) complex
operator/(complex) private double real,
imag
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Implementation
complexcomplex() //default constructor
realimag0 complex complexoperator(comple
x c) complex temp temp.real
c.real real temp.imag c.imag
imag return temp
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Implementation - Continued
complex complexoperator/(complex c)
complex temp temp.real (realc.real
imagc.imag)/( pow(c.real,2) pow(c.imag,2)
) temp.imag (imagc.real -
realc.imag)/( pow(c.real,2) pow(c.imag,2)
) return temp
42
Test Program
complex c1, c2, c3 //declare three complex
variables c1.input(cin) c2.input(cin) //test
addition c3 c1 c2 cout ltlt endl ltlt "c1 c2
is " c3.print(cout) //test division c3 c1 /
c2 cout ltlt endl ltlt "c1 / c2 is
" c3.print(cout) cout ltlt endl
43
Sample Output
for input 4.4 1.5 3.5 -2.5 The output from our
test program will be c1 c2 is 7.9 -1i c1 /
c2 is 0.62973 0.878378i