Review for Exam 3

1
Review for Exam 3

• arrays
• strings
• files
• classes

2
Chapters covered

• Hanly
• Chapter 6
• skip sections 1, 7
• Chapter 7
• skip section 6
• Chapter 9

• Friedman-Koffman
• Section 3.7
• Chapter 8
• Chapter 9
• not section 7
• Chapter 10
• Section 11.7

Don't forget that there are web notes about all
of these http//cs.boisestate.edu/tcole/cs117/not
es.html
3
Arrays

• a collection of values/objects of the same type
• they can be of any type
• int values20
• sets aside memory for 20 integers
• The elements are accessed by putting the index of
  the element in square brackets, e.g. values3
• For an array declared to have n elements, the
  array index runs from 0 to n-1
• You have to keep track of how many of the array
  elements have been assigned values.

4
For arrays, know how to

• declare an array
• int score30
• initialize an array when it is declared
• double x 1.9, 2.8, 3.7, 4.6, 5.5
• access an element of the array
• score3
• first element has index 0

5
Array know how cont.

• use a loop to do something with every element of
  the array
• for (int i0 iltnumElements i)
• sum sum scorei
• pass the entire array to a function
• highScore max( score, nstudents)

6
C-style strings

• A C-style string is an array with elements of
  type char
• It should be terminated with the null character
• character whose ASCII code is 0
• '\0'
• Some useful functions for using C-style strings
  are in ltstring.hgt

7
C-style Strings know how to

• declare a C-style string
• char cstr6
• this can hold 5 characters plus the termination
  character
• access an element of a C-style string
• array index starts at 0
• ith element is cstri-1
• initialize a C-style string when you declare it
• char dstr7"bat"
• number of elements optional in this case

8
I/O for C-style strings

• input a C-style string with gtgt
• get next sequence of non-space characters from
  the input stream
• get multiple words with
• istreamgetline( char, int)
• output a C-style string with ltlt

9
string.h

• strlen - returns number of characters in the
  string
• doesn't count the null character
• strlen(dstr) will return 3
• strcpy - to copy a string into another one
• strcpy( cstr, "man") will put man into cstr
• strcat - to append one string onto another
• strcat( dstr, cstr) puts "batman in dstr
• strcomp - for comparing two string
• returns 0 if they are the same
• strcomp( dstr, cstr) will be non-zero
• strcomp( cstr, "man") will return 0

10
C string class

• An object-oriented way to work with text strings
• include ltstringgt
• You can
• declare a string
• string str1
• initialize a string when you declare it
• string str2("two")
• access an element of a string
• the ith element is strI-1 or str1.at(i-1)
• get the length with str1.length()

11
C string class operators

• input a string with gtgt - get a sequence of
  non-space characters
• output a string with ltlt
• assign a value using
• str1 "one"
• compare using familiar operators
• str1 str2
• str2 lt str1
• concatenate with
• str1 str2

12
File I/O

• include ltfstream.hgt
• classes
• ifstream for input
• ofstream for output
• Constructors
• default
• initializing takes c-string filename

13
File I/O

• functions you should know how to use
• open( char filename)
• eof() - to test for end of file
• fail() - to test for all errors
• close()
• read/write the same as for cin/cout

14
iomanip

• setiosflags(iosflagname) resetiosflags(iosflag
  name)
• right / left
• fixed
• scientific
• showpoint
• setw( int fieldwidth)
• setprecision( int digits)

15
Class Declaration

• what member variables are needed
• data needed to represent the object
• what functions are needed
• functions represent behavior and/or services

16
Form of declaration

• class aClass
• public
• aClass() // zero parameter constructor
• aClass( int v1, double v2)
• int getVar1() const // accessors
• void setVar2( double d) // mutator functions
  
• private
• int var1
• double var2
• friend operatorltlt( ostream , const Angle )

17
Class functions

• constructors used to initialize objects
• name of constructor is same as the class name
• member functions
• accessors provide read-only access to member
  variables
• mutators allow user to change member variables
• friend functions
• overloaded operators

18
Functions associated with classes

• overloaded operators provide arithmetic and/or
  comparisons in same ways as for numbers
• friend functions allowed access to the private
  members of the class

19
Member functions

• function declarations (prototypes) go into class
  definition
• function definitions
• usually outside of class definition (need scope
  resolution operator )
• inline definitions (usually very short) are
  contained in the class definition and don't need
  the scope resolution operator

20
Member Function Signatures

• Inside the class definition, prototypes look just
  like those of a regular function
• double someFunction( int param1, int param2)
• member function has access to
• member variables
• parameters
• any locally declared variables

21
Member Function Definitions

• The function definition contains the code that is
  executed when the function is called.
• double aClassmemberFunction( int param1, int
  param2)
• // code that is executed
• return aDouble
• scope resolution operator aClass indicates to
  the compiler that this is a member function of
  class aClass

22
Declaring Objects

• You declare an object by giving the className
  (its type) and a variable name.
• theClass obj1
• This calls the zero parameter constructor
• You can initialize an object when you declare it
  by providing arguments
• theClass obj2( 12, 3.4)
• This calls a constructor which has int and double
  parameters.

23
Calling member functions

• From outside the class, you call a member
  function using the . operator
• double x obj1.someFunction( arg1, arg2)
• Inside the class, only need the . operator for an
  object other than the current one
• You use overloaded operators the same way you
  always use operators
• obj1 lt obj2
• cout ltlt obj1

24
Things to remember

• member variables should not be passed to member
  functions
• these functions already have access to them
• all class members are private unless they appear
  in the public section of the class definition
• private members are not directly accessible from
  outside the class
• don't redeclare the member variables
• they are declared in the class declaration
• member functions that use only member variables
  need no parameters

25
Member Functions

• accessor functions (get functions) return the
  values of the member variables
• don't always have one for every member variable
• provide set functions if you want the user of the
  class to be able to change the value of a member
  variable