lecture 4

Question 1

what is a class ??

Answer 1

• class is a data type (like string or double),
• its variables are called objects.
• some predefined classes :- int , char , iostream

Question 2

whats included in a class definition ?

Answer 2

• description of the kinds of values that the variables (objects) can hold
  for example :- double gpa , string student_name
• description of the member functions

Question 3

whats a struct ?

Answer 3

struct is like a class but with no member functions

Question 4

put labels on this struct:-

struct CDAccount
{
double balance ;
double interest ;
int term ;
} ;

Answer 4

struct CDAccount //struct definition
// CDaccount is the structure tag /type
{
double balance ;
double interest ; // member names are identifiers
int term ;
} ;

Question 5

does the struct have a value ?

Answer 5

it consists of the values of its member variables

Question 6

how do you specify (نحدد) memeber variables called (balance , rate , term) of a struct? write the syntax given the following struct declaration :-

CDAccount my_account, your_account ;

Answer 6

my_account . balance
your_account . rate
my_ account . term

Question 7

how do we use structs as arguments in function calling ?

use a call by reference for a struct datetype called CDaccount with member variable named acc1, for a function called GET_DATA that doesnt return a value.

Answer 7

void GET_DATA (CDaccount & acc1 ) ;

Question 8

writea function named SHRINK_WRAP that takes 2 arguments of type double named balance and rate and returns a structure data type named CDaccount

Answer 8

CDaccount SHRINK_WRAP (double balance, double rate)

Question 9

what does the following line do ??

CDaccount my_account , your_account ;
your_account = my_account ;

Answer 9

Assigns all member variables (balance , rate ,interest) in your_account the
corresponding values in my_account

Question 10

what are heirarchical strutures?

Answer 10

structures that contain member variables that are also structures

example:-

struct personinfo
{
double height;
int age;
date birthday; // date is a structure data type
};

struct date
{
int month;
int day;
int year;
};

Question 11

given the following struct :-

struct Date
{

int month;
int day;
int year;

};

declare and initialize a due_date object of data type Date to the following values 12 /31 /2004

Answer 11

date due_date = { 12, 31,2004}

Question 12

what does the ennumeration data type represent ?

Answer 12

ennum data types have values defined by a list of CONSTANTS of type int

for example :-

enum month_legnth
{
JAN = 31,
FEB = 28,
….
DEC = 31
};

Question 13

Write a definition for a structure type for records
consisting of a person’s wage rate, accrued vacation
(in whole days), and status (hourly or salaried).
Represent the status as one of the two character
values ‘H’ and ‘S’.

Answer 13

struct
{
double wage_rate ;
int accured_vacation ;
char status ;
};

Question 14

what numeric values are assigned to the following enum ?

enum Direction {NORTH, SOUTH, EAST, WEST}

Answer 14

the numeric values are not specified,so, the identifiers (north , south ,east,west) are assigned consecutive values starting with 0 till 3

Question 15

• By default, the first enumerator has a value of ……?
• Each successive enumerator is ………..larger than
  the value of the previous one, unless you ………….?

Answer 15

• zero
• one
• explicitly specify
  a value for a particular enumerator

Question 16

Why are the following illegal declarations?
enum grades{‘A’, ‘B’, ‘C’, ‘D’, ‘F’} ;
enum places{1st, 2nd, 3rd, 4th} ;

Answer 16

first one should be
enum grades{A, B, C, D, F};

second one , variables identifiers can’t start with numbers

Question 17

what is a typedef statement ? and what’s its syntax ?

Answer 17

a typedef is a way of renaming a type

Syntax:
typedef existing_type_name new_type_name ;

Example:
typedef int Boolean;

the type was integer then became boolean

Question 18

what is a class ?

Answer 18

a data ype with object as variables

Question 19

whatdoes the definition of a class include ?

Answer 19

• Description of the kinds of values of the member
  variables
• Description of the member functions

Question 20

syntax for member function definition ??

Answer 20

Returned_Type Class_Name :: Function_Name (Parameter_List)
{
Function Body Statements
}

Example :-

void DayOfYear :: output( )
{
cout < < “month = “ < < month
< < “day = “ < < day < < endl ;
}

Question 21

Member function definitions identify the ………….
in which the function is a member

Answer 21

• class

Question 22

◼ ‘::’ is the ………….operator
◼ it tells the ……… a member-………… is a member of it
◼ void DayOfYear::output( ) indicates that function
output is a member of the DayOfYear class
◼ The class name that precedes ‘::’ is a ………………

Answer 22

• scope resolution
• class , function
• type qualifier

Question 23

◼ ‘::’ used with …………. to identify a …………………..
void DayOfYear::output( )
{
// function body
}
◼ ‘.’ used with ……….. to identify a ………….
DayOfYear birthday;
birthday.output( )

Answer 23

• classes
• member function
• variables
• member functions

Question 24

what is encapsulation??

Answer 24

Encapsulation is
Combining a number of items, such as :-
variables + functions
into a single package
such as :-
an object of a class

Question 25

private members of a class can only be referenced
within the ………………………….

……………………….cannot be accessed directly
by the program

Changing their values requires the use of ………………………. of the class

Private variables require member functions to
perform all changing and retrieving of values
like ……….functions allow you to obtain the
values of member variables
and …………functions allow you to change the values
of member variables

Answer 25

• definitions of member functions
• private variables
• public
  member functions
• accessor
• mutator

Question 26

• Calling Public Members: object . publicFunction () ;
• When a member function calls a private
  member function, object name is NOT used

Answer 26

fraction (double percent);
void BankAccount::update( )
{
balance = balance + fraction(interest_rate)* balance;
}

//fraction is a private member of the BankAccount class
// fraction is called by member function update