Programming in C

1
Programming in C

• The Turbo C Environment
• C Program Structure
• Modular Programming with Functions
• C Control Structures
• Advanced Data Types
• Classes

2
Turbo C Environment

• Windows based product
• Integrated Development Environment (IDE)
• editor
• compiler
• linker
• debugger

3
Structure of a C Program

• preprocessor directives
• main function header
• declare statements
• statements

4
Using the Turbo C IDE

• tool bars
• menu
• editor

5
Using the Turbo C IDE (2)

• compiling
• linking
• executing

6
Developing Programs

• Understand the problem
• Design a solution to the problem
• including test cases and the solutions to the
  test cases
• Implement and document
• Translate the solution to a programming language

7
Developing Programs (2)

• Verify
• Test and debug the solution
• using test cases from design phase
• Maintain

8
Problem Solving (1)

• consider a trapezoid -- 4 sided figure in which
  two sides are , the area is 1/2 the product of
  the height and the sum of the lengths of the two
  bases.

b1
h
b2
Area (b1 b2)h/2
9
Problem Solving -- Trapezoid Pseudocode

• input b1
• input b2
• input height
• bases b1 b2
• area bases h /2
• output area

10
Problem Solving (2)

• consider finding the area and circumference of a
  circle
• pi 3.14159
• area pi radius2
• circumference 2 pi radius

11
Problem Solving -- Circle Functions Pseudocode

• pi 3.14159
• input radius
• circum 2 pi radius
• area pi radius radius
• output area
• output circum

12
Problem Solving (3)

• consider converting temperatures from Centigrade
  to Fahrenheit (or vice versa) where
• c 5/9(f-32)
• f 9/5c 32

13
Problem Solving --Temperature Conversion
Pseudocode

• input temp
• input scale
• if scale f
• newtemp 5/9 (temp-32)
• else
• newtemp 9/5 temp 32
• output newtemp

14
Problem Solving (4)

• consider sales commissions based upon the number
  of sales made during the time period
• 8 per sale for lt 15 sales
• 12 per sale 15 sales
• 16 per sale gt 15

15
Problem Solving -- Commission Pseudocode
quota 15 input number_sales if number_sales lt
quota rate 8 else if number_sales quota
rate 12 else rate
16 com rate number_sales output com
16
Problem Solving -- Commission Pseudocode Multiple
Salespeople
quota 15 input number_salespeople
17
Problem Solving -- Pseudocode Multiple
Salespeople (2)
loop number_salespeople times input
number_sales if number_sales lt quota rate
8 else if number_sales quota
rate 12 else rate
16 com rate number_sales output com
18
Exercise -- GO

• Develop a series of problems for the students to
  do using each of the statement types

19
Introduction to the C Language

• keywords
• C is case-sensitive
• identifiers
• can not be keywords
• comments
• enclosed in / / multi-line
• start with // single line

20
Preprocessor Statements

• library header files -- include
• lt gt -- system library
• include ltiostream.hgt
• -- personal library
• include apstring.h

21
Data Types and Declarations

• declare statement
• allocates memory and assigns name
• data type name initial value
• int -- 2 bytes
• float -- 4 bytes
• double -- 8 bytes
• char -- enclosed in

22
User Defined Data Types

• class -- mechanism to establish new data types
• ap classes
• string
• apstring.h apstring.ccp
• bool
• bool.h

23
Example Declare Statements

• int a
• int a,b,c
• float x,
• y
• double average 0.0

• char answer Y
• bool another
• bool more false
• apstring name
• apstring
• class C

24
Input and Output Statements

• include ltiostream.hgt
• cout -- output
• ltlt insertion character
• cin -- input
• gtgt extraction character

25
Using APSTRING Class

• include apstring.h
• entire path
• create project
• place apstring and program in project
• you will need a different project for each program

26
Input and Output Statements (2)

• COUT -- control codes
• way of inserting placement control
• \n -- new line
• \t -- tab
• iomanip.h
• contains more formatting methods

27
Arithmetic in C

• operator precedence
• ( )
• , /, (left to right)
• , - (left to right)
• integer arithmetic
• operations involving integers yielding integer
  results
• truncation on integer division
• -- modulo operator

28
Arithmetic in C (2)

• mixed mode arithmetic
• operands of different data types
• hierarchy double/float/int
• highest mode is used
• determined on a operation by operation basis

29
Assignment Statements

• assignment operator
• operator precedence and mixed mode arithmetic
  hold
• combination operators
• , -, , /,
• variable expression

30
Increment and Decrement Statements

• special operators which add or subtract one from
  a variable
• more efficient (generates inc, dec)
• a gt a a1
• a-- gt a a -1
• postfix (a) (a--)
• done after the expression is evaluated
• prefix (a) (--a)
• done prior to evaluating the expression

31
Type Casting

• changes the evaluation data type of the
  expression
• does not change the data type of the variable
• (data type)
• (int)
• (float)
• (apstring)

32
Programming Problems

• convert distance in miles to distance in
  kilometers and meters
• 1 mile 1.61 km, 1 km 1000 meter
• convert a temperature in Celsius to Kelvin
• -273.15oC 0oK
• convert a temperature in Fahrenheit to Kelvin
• -459.67oF 0oK

33
Mathematical Functions (math.h)

• code reuse
• sqrt, pow, exp, log, log10
• abs, ceil, floor
• trigonometric functions

34
Programming Problems

• determine the volume of a sphere with an input
  radius
• volume (4 pi radius3)/3
• determine the area of a triangle when given
  length of two sides and the included angle in
  degrees
• degrees 180 radians / pi
• area side1 side2 sin (radians) / 2

35
Programming Problems (2)

• determine the distance from a point on the
  Cartesian plane to the origin
• distance sqrt (x2 y2)

36
Exercise -- GO

• Implement the sequential problems developed in
  the first exercise

37
Modular Programming with Functions

• designed in small segments
• each segment implemented as a function
• sqrt, pow, sin
• self contained
• requires input through parameters
• sends output through name
• Abstraction
• know what the function does and what it needs to
  do its task
• not how the function works

38
Modular Programming with Functions (2)

• allows for reuse
• eliminates redundancy
• allows for team development
• simplifies logic

39
Form of a Function
return data type Function name (parameter
list) declarations statements return
40
Types of Functions

• no input, no return value
• void
• input but no return value
• both input and output
• no input but returns a value

41
Example -- Circle Functions

• calculate the area and circumference of a circle
  of an input radius
• input radius
• calculate area
• calculate circumference
• output results
• invoke the functions
• use name and parameters in an expression
• functions must be defined before they can be used

42
Example -- Pythagorean Triples

• Pythagorean Triple are the three sides of a right
  triangle a,b,c
• a2 b2 c2
• given m and n, such that mgtn we can generate the
  triples
• a m2 - n2
• b 2mn
• c m2 n2

43
Call by Value

• on invocation the value of the actual parameter
  is copied into the formal parameter
• when the function terminates the value IS NOT
  copied back to the actual parameter
• can not change the value of a parameter within
  the function

44
Example Call by Value
include ltiostream.hgt int test (int n) int i
5 n i return (n)
void main (void) int n1, i i test
(n) cout ltlt i ltlt ltlt n ltlt endl
45
Example Call by Value (2)
main
test
1
n
1 6
n
i
i
6
5
46
Functions -- Pass by Reference

• returns 0 or 1 value through name
• need to return more than 1
• swap the values of two variables
• change the values of parameters
• bank deposit or check
• pass the name of the parameter rather than its
  value so that the function uses the same memory
  location as the actual parameter

47
Reversing Order -- Swap

• if (num1 lt num2)
• temp num1
• num1 num2
• num2 num1

48
Reference Parameters

• Parameter which shares the memory of the actual
  parameter rather than declare new memory and copy
  the actuals value into it
• Parameter declaration
• int x
• x is an alias for the actual integer parameter
• double y
• y is an alias for the actual double parameter

49
Function Swap

• void swap (int num1, int num2)
• int temp
• temp num1
• num1 num2
• num2 temp
• if a gt b
• swap (a,b) to invoke the function

50
Call by Value vs Reference

• Use reference vs return type
• all input
• when need to return more than 1 value
• always have return type void
• Use value
• all other cases
• no side effects

51
Exercise

• modify circle.cpp to use reference where
  appropriate
• modify pyth.cpp to have compute_sides

52
Programming Problem -- Functions

• program to convert Fahrenheit to Celsius,
  Fahrenheit to Kelvin
• input the temperature in Fahrenheit
• use functions
• input Fahrenheit temperature
• convert to Celsius
• convert to Kelvin
• output the results

53
Programming Problem -- Functions

• Translate US prices from pennies per pound to
  Canadian prices dollars per kilogram
• 1 pound .4536 kilograms
• 1 dollar US 1.26 dollars Canadian
• Input 5 words, echoing each as it is input and
  display the average length (number of characters)
  per word

54
Exercise -- GO

• Implement all previous programs using modular
  design and reference and value parameters as
  appropriate

55
Function Prototypes

• a function must be declared before it can be used
• placed functions at top of program
• create prototype (declaration of interface),
  place it at the top and the functions
  implementation can be placed after the main
  function
• return value function name (parameter list)
• float get_radius ()

56
Overloading

• function names can be overloaded
• different interfaces
• compiler can determine which to execute
• operators can be overloaded as well

57
Selection Structures

• execute a group of statements based upon a
  condition being true or false
• if (condition)
• statement
• if (condition)
• statement(s)
• conditions -- relational operators
• lt, gt, lt, gt, , !

58
Simple Selection Examples

• if (hours gt 40)
• cout ltlt overtime!\n
• if (cost gt 30000)
• tax (cost - 30000) tax_rate
• cout ltlt \n for a car costing ltlt cost ltlt
• a luxury tax of ltlt tax ltlt is due

59
Selection -- IF ELSE

• if (condition)
• statement
• else
• statement
• if (condition)
• statements
• else
• statements

60
If ELSE -- Examples

• if (xgty)
• max x
• else
• max y

61
If ELSE -- Examples (2)

• if (hours lt 40)
• gross_pay wage hours
• else
• overtime_hours hours -40
• overtime_pay wage overtime_hours 1.5
• gross_pay wage 40 overtime_pay

62
Programming Example

• find the reciprocal of an integer
• undefined for 0
• attempt to divide by 0 will cause program
  termination
• recip.cpp

63
Programming Exercise

• Modify the program which finds the roots of the
  quadratic equation so that it will not error
  terminate
• quad.cpp

64
Logical Operators

• combine two or more relational operators to
  create complex relations
• AND --
• OR --
• NOT -- !
• precedence before

65
Conditional Operators -- Examples

• if (temp_type F temp_type f)
• centigrade convert_cent (temp)
• kelvin convert_kelvin (temp)
• If (num gt 0 num lt 10)
• cout ltlt single digit number\n

66
Short Circuiting

• efficient evaluation of Boolean expression
• AND
• the first relational expression which evaluates
  false terminates the evaluation-- result false
• OR
• the first relational expression which evaluates
  as true terminates the evaluation -- result true

67
Short Circuiting (2)

• determine if a number is divisible by another
  number
• if the second number is 0 -- error termination
• if (a ! 0 b a 0)
• if a 0 the second expression is not evaluated

68
Programming Example

• determining leap years
• leap years occur every 4 years, if the year is
  divisible by 4
• only valid for non-centennial years
• centennial year (divisible by 100) which is
  divisible by 400

69
BREAK statement

• allows program to leave a control structure
• form -- break

70
Multiple Selection -- Switch

• test the value of a single integer type and
  perform different blocks of statements based upon
  the value

71
Multiple Selection -- Switch Form

• switch (expression)
• case value 1
• statement(s)
• break
• case value 2
• statement (s)
• break ....
• default
• statement(s)
• break

72
Example Switch Statement

• determine if a value is -1, 0, or 1-4
• cin gtgt value
• switch (value)
• case -1
• cout ltlt value -1\n
• break
• case 0
• cout ltlt value 0\n
• break

73
Example Switch Statement Cont

• case 1
• case 2
• case 3
• case 4
• cout ltlt value in range 1-4\n
• break
• default
• cout ltlt value is lt -1 or gt 4\n

74
Example Programming Problem

• color compliments
• clswitch.cpp

75
Programming Problem

• complete temperature conversion program
• accepts as input a temperature and a type and
  converts it to the other two temperature types
• prints an error message if unknown type
• accepts both upper and lower case input

76
Exercise -- GO

• Implement the selection statement problem
  solving problems

77
Repetition Statements

• ability to repeatedly execute blocks of
  statements
• two types of loops
• count controlled
• executed a set number of times
• event driven
• executed until a certain event occurs
• pre-test and post-test loops

78
While Loop

• form
• while (condition)
• statement(s)
• event driven loop

79
While Loop (2)

• pre-test (0) loop
• test the condition
• if true execute the loop
• if false exit loop
• loop can be executed 0 times

80
Example While Loop

• i 5
• while (i gt 0)
• cout ltlt i ltlt endl
• i--

81
Programming Example

• taking averages
• enter values to be averaged until sentinel is
  entered (0)
• event which terminates loop
• ave.cpp

82
Controlling Input

• 0 is in the set to be averaged
• must use some key defined value to signal end of
  input
• CRTL Z
• get()
• cin.get()
• accepts a single value as input
• prompt for CRTL () Z

83
Do While Loop

• event driven loop
• always executes at least once (1 loop)
• post test loop
• form
• do
• statement(s)
• while (condition)

84
Do While Loop (2)

• executes the loop
• tests the condition
• if true executes the loop again
• if false exits the loop

85
Do While Example

• add the numbers from 1 to 5
• sum 0
• i 1
• do
• sum i
• i
• while (i lt 5)

86
Programming Example

• display square of input value
• user prompt to continue
• squares.cpp

87
Programming Example -- Circle Functions

• robust programming
• user friendly/user forgiving
• Area and Circumference of circle
• radius can not be lt0
• present error message and re-prompt for input
  until it is valid
• circleif.cpp

88
Programming Exercise -- Pythagorean Triples

• robust example
• m gt n and both gt 0
• give meaningful error message

89
For Loop

• counted loop -- set number of times
• iterates through a set of values
• for (initial expression
• condition
• loop expression)
• statement(s)

90
For Loop (2)

• initial expression -- starting point, executed
  once before the loop begins
• condition -- evaluated each time through the loop
  (pre test)
• exit -- false
• execute -- true
• loop expression -- statement(s) executed at the
  bottom of the loop

91
Example For Loop - I

• Countdown
• for (i 1 ilt5 i)
• cout ltlt i ltlt endl

92
Example For Loop - II

• sum numbers 1-5
• for (sum 0, i 1 i lt 5 i)
• sum i

93
Programming Examples

• Factorials
• fact.cpp
• change fact to be integer (see what happens)
• temperature conversions
• temps.cpp
• generating random numbers
• random.cpp

94
Boolean Variables

• Turbo C does not have Boolean
• bool.h -- apclass
• 0 false, 1 true
• bool flag
• if flag (if 0 false, non 0 true)
• while !flag
• flags.cpp

95
Programming Exercise

• maintain check book balance
• modular
• 15 service fee for bad check
• display message
• final balance on exit

96
Nesting Control Structures

• both selection and repetition statements can be
  nested for complex execution
• if else if
• else matches closest un-elsed if
• all looping structures can be nested regardless
  of type

97
Example If else if -- Sales Quotas

• if (num_sales lt quota)
• rate low_rate
• else if (num_sales quota)
• rate ave_rate
• else rate high_rate

98
Example Nested Loops

• cout ltlt enter the number to sum to, 0 to end
• cin gtgt num
• while (num ! 0)
• for (sum0, i1 iltnumi)
• sum num
• cout ltlt the sum of the numbers 1 - ....
• cout ltlt enter the number to sum to ...
• cin gtgt num) /end while/

99
Nesting Control Structures Programming Examples

• counting number of letter grades
• aven.cpp
• printing multiplication tables
• table.cpp
• circle functions
• circleof.cpp

100
Programming Exercise

• Modify the average program so that more than 1
  set of averages can be determined
• Modify the Pythagorean triples so that an
  unlimited number of triples can be generated
• Modify finding roots of a quadratic equation so
  that all root types are determined

101
Enumeration Types

• user defined data type
• enum statement
• define the domain
• enum bool false, true
• bool -- name of data type
• false, true -- domain
• integers
• false 0, true 1

102
Lines in Cartesian Plane

• perpendicular, parallel or intersecting
• slope
• enumeration type can be used
• parameters
• return types
• lines.cpp

103
Exercise -- GO

• Implement any remaining problem solving programs.
• Be sure have a complete set identifying all
  structures including enumeration types.

104
Composite Data Structures

• construct that can access more than one data item
  through a single name
• Array -- homogenous data type
• Structure -- heterogeneous data type

105
Arrays\Vectors

• collection of data components
• all of same data type
• are contiguous
• accessed
• entire array (name)
• individual component (subscript)

106
Declaring Arrays

• int x5
• declares a 5 element array of integers
• x0, x1, x2, x3, x4
• int x25 -- two dimensional array
• int x 2 5 5 -- three dimensional array
• size must be declared at compile time
• can not int size, int xsize
• can
• define max_size 100
• int xmax_size

107
Referencing Arrays

• elements
• float ave_temp 12
• ave_temp 0 -- Jan
• ave_temp 11 -- Dec
• ave_temp i2
• no arrays bounds checking
• fast code

108
Initializing Arrays

• int x5 12,-2,33,21,31
• int height 10 60,70,68,72,68
• rest 0
• float g 3.2,5.7
• size is set to 2
• a 250 element array all to 1
• int x250
• for (i 0 ilt249 i)
• xi 1

109
Using Arrays

• data must be passed more than once
• array1.cpp
• implement vectors or matrices
• array2.cpp
• data comes in haphazard order
• string example

110
Passing Arrays to Functions

• pass an element
• treated as any single variable of that type
• pass by value
• pass the entire array
• use the name without any subscripting
• pass by reference
• pass the address and the actual memory locations
  of the actual array are used by the function
• any change made to the elements of the array by
  the function WILL be noted in the main program

111
Programming Problem

• Input a set of exam scores for a class
• calculate and display
• average
• high grade
• low grade
• those grades which were above the average
• have number of grades entered determined by the
  of values input rather than prompt for class size

112
Programming Problem

• Using an enumeration type for months of the year
• calculate the average rainfall
• display those months with lt average rainfall
  amounts

113
Structures

• Heterogeneous data type
• logically related set of items which can be
  accessed either on an individual item basis or
  all at once through structures name
• fields can be of any data type (different ones),
  user defined as well

114
Example Structure

• struct GRADES
• apstring name
• int midterm
• int final
• float assigns
• float sem_ave
• char letter_grade
• GRADES student1, student2

115
Operations on Structures

• Assignment
• entire structures done by common elements, in
  order
• single element -- data type
• Initialization
• on declare
• FRACTION num1 1,2
• GRADES student1 john Doe,90,80,70,80

116
Structures and Functions

• An element is passed to a structure in the same
  way any simple variable is passed
• by value (default) or by reference (forced)
• student.cpp
• An entire structure is passed
• by value (default)
• by reference (force) employee.cpp
• A function can return a structure variable

117
Arrays and Structures

• Structures can contain vectors, apstring
• apstring name
• apvectorltintgt exams(3)
• vectors of structures
• apvectorltGRADESgt class(60)
• 60 students in class
• class0.name class0.final
• class59.name class59.final

118
Hierarchical Structures

• Structures can contain structures
• typedef struct
• char last 15
• char first 15
• char middle NAME
• typedef struct
• NAME stu_name
• STUDENT

119
Arrays\Vectors

• collection of data components
• all of same data type
• are contiguous
• accessed
• entire array (name)
• individual component (subscript)

120
Declaring Vectors

• include aapvector.h
• apvectorltintgt v1(10)
• declares a 10 element integer vector
• v10, v11, v12.v19
• apvectorltintgt v2(10,0)
• declares a 10 element integer vector
• all elements are initialized to 0
• v200, v210..v290

121
Declaring Vectors (2)

• apvectorltapstringgt (25)
• declares a vector of 25 strings
• each is empty string
• can be user defined data types

122
Accessing Elements

• v11
• second element of the vector
• v19
• last element of the vector
• v11 2
• high v13

123
Assignment -- APVECTOR

• Apvectorltintgt v1(10), v2(20)
• v1 v2
• v1 will be reallocated at a size of 20
• v10 v20
• .
• v119 v219
• corresponding elements will be assigned

124
Member Functions -APVECTOR

• User defined data type -- class
• length() -- capacity of vector
• size changes as needed
• returns current size as an integer
• object.length()
• v1.length() gt 20
• v1 still ranges from 0-19
• for (i0iltv1.length()i)
• cout ltlt v1i ltlt endl

125
Vectors as Parameters

• elements are considered same as any single
  variable
• entire vector
• pass by value or by reference
• more efficient to pass by reference
• avoid side effects
• const reference parameter

126
Using Vectors

• data must be passed more than once
• vect1.cpp
• implement vectors or matrices
• vect2a.cpp
• data comes in haphazard order
• string example
• enumeration types and vectors
• rainenum.cpp

127
Matrices

• two dimensional array
• problems with C arrays are doubled in two
  dimensions
• APMATRIX
• include aapmatrix.h
• can automatically be resized
• subscript checking

128
Declaring Matrices

• apmatrixltintgt imat (3,3)
• imat00 ....imat 22
• apmatrixltintgt imat2(3,3,0)
• all elements are initialized to 0
• can be any system or user defined data type

129
Referencing Elements

• imat12 7
• score imat ij
• if subscript is out of bounds (either of them)
  program error terminates

130
Assignment -- APMATRIX

• apmatrixltintgt imat2(10,10)
• imat imat2
• imat 3x3
• imat2 10x10
• after assignment imat 10x10
• assigns corresponding elements

131
APMATRIX--Member Functions

• numrows() -- returns the number of rows
• imat.numrows() gt 10
• numcols() -- returns the number of columns
• imat.numcols() gt 10
• for (r0rltimat.numrows()r)
• for (c0cltimat.numcols()c)
• cout ltlt imatrc

132
Programming Problem

• Create resuable functions for matrix addition
  and multiplication
• matrix.h
• matrix.cpp
• use_matrix.cpp

133
ADT -- complex numbers

• struct COMPLEX
• double real
• double imag
• operations -- input, output, add, subtract, mult,
  divide, absolute value
• package together in include file

134
Class -- User Defined Data Type

• encapsulate data and functions
• information hiding
• public vs private
• can be inherited
• structures can not

135
Public VS. Private

• client programs can use the member functions
  which come with a class through the public
  interface
• client program CAN NOT access any function or
  data member declared private
• information hiding
• if cant access it, cant modify it
• more maintainable -- fewer side effects

136
Class Definition

• class class_name
• public
• member functions
• private
• data members

137
Data Members

• Pieces of information which the class maintains
• states
• date -- month, day, year
• complex number --- real, imaginary
• fraction -- numerator, denominator
• student -- name, ssn, address, etc
• Private-- only the functions of the class have
  access to them

138
Member Functions

• Services provided by the class to manipulate the
  data members
• Public -- can be used by any client program
• Have access to the data members
• Constructors, Accessors, Mutators, and Operations

139
Constructors

• Automatically invoked by the system when an
  object of the class is declared
• specify the initial values to be given to the
  data members
• function with the same name as the class itself
  with no return type of any kind
• can be overloaded

140
Accessors

• Return the value of a data member
• Const functions as they do not change the value
  of any data member
• Necessary since no outside function can access
  the data members

141
Mutators

• Modify one or more of the data members
• used by client programs to modify the data
  members, since client programs can not access the
  data members directly

142
Operations

• Provide services of the class
• perform calculations, etc using data members
• necessary since the data members are not
  accessible to the client programs

143
Date Class

• Data members
• int day, int month, int year
• Constuctor
• allow date to be set when the object is declared
• or to use default values
• small implementation of the class
• demonstration purposes only

144
Interface of the Date class

• Definition of the class
• available to client programs/ers
• .h file
• declaration of the data members
• interfaces of the member functions
• the object receiving the message to invoke the
  member function is the one that the function
  operates upon

145
Date Class Implementation

• .cpp file
• the implementation of all member functions
• scope resolution operator
• since the function implementations are in a
  separate file need to tie them back to the class
  or they will not have access to the data members

146
Client Program

• Declares an object of the data type
• Date today
• Invoke a member function
• object.function_name()
• object which receives the message is the one on
  which the function the function operators
• v1.resize()
• v1.length()

147
Constructor

• Default initial values for parameters
• if the parameters are omitted the initial value
  of the fraction on declaration is 1/1
• initialization list
• special form of the constructor which allows the
  data members to be set within the interface (.h
  file)

148
Fraction Class

• Represents rational numbers
• constructor
• initializes object to 1/1
• accessors
• reduce
• print_fraction

• Mutators
• input_fraction
• operations
• add, subtract, multiply, divide
• gcd
• needed by class to do its work

149
Member vs Friend functions

• Member function must be invoked with object
  receiving message
• friend function stands separate
• it still has access to the data members
• does not need an object to be invoked
• used for binary operators which do not modify
  their parameters (overloading)
• defined in interface as friend

150
Complex Number Class

• class COMPLEX
• public
• COMPLEX(int r0,int i0)
• int real() const
• int imaginary() const
• COMPLEX add_complex
• (const COMPLEX l, const COMPLEX r)

151
Complex Number Class Cont

• COMPLEX sub_complex
• (const COMPLEX l, const COMPLEX r)
• COMPLEX mult_complex
• (const COMPLEX l, const COMPLEX r)
• COMPLEX div_complex
• (const COMPLEX l, const COMPLEX r)

152
Complex Number Class -- Cont

• void set_real (double)
• void set_imag(double)
• private
• double real
• double imag

153
Member vs Friend functions

• Member function must be invoked with object
  receiving message
• friend function stands separate
• it still has access to the data members
• does not need an object to be invoked
• used for binary operators which do not modify
  their parameters (overloading)
• defined in interface as friend

154
Inlining

• Used to provide an implementation within the
  interface
• Only use on small simple functions which either
  simply set data members or simple calculations
  which return values

155
This pointer

• Refers to the object receiving the message
• this gt value
• used in functions which modify the object
  receiving the message ,-,,/

156
File I/O

• Input and output are done through streams
  istream and ostream (fstream.h)
• cin -- istream -- iostream.h
• cout -- ostream -- iostream.h
• 4 steps to using files
• declare an object of the appropriate stream
• open the stream
• connects the external file with the stream
  (buffer)
• stream.open(filename)

157
File I/O(2)

• Input gtgt but from the stream declared rather than
  from cin
• output ltlt but from the stream declared rather
  than cout
• close file
• stream.close()