1
Simple Data Types,Built-in and
Use-Defined
2
Chapter 10 Topics
Built-In Simple Types
Integral and Floating Point Data Types
Using Combined Assignment Operators
Prefix and Postfix Forms of Increment and
Decrement Operators
Additional C++ Operator
Character Sets
Using an Enumeration Type
Creating and Including User-Written Header Files
3
Built-In Simple Types
Simple(atomic)data type:
A data type in which each value is
atomic(indivisible).
Example,
a single character of type char is atomic,
but the string,Good Morning” is not,
4
C++ Simple Data Types
simple types
integral floating
char short int long bool enum float double long double
unsigned
5
By definition,
the size of a C++ char value is always 1
byte,
exactly one byte of memory space
Sizes of other data type values in C++ are
machine-dependent,
‘ A?
6
Example
On one machine,it maybe the case that
sizeof(char)=1; sizeof(short)=2;
sizeof(int)=4; sizeof(long)=8;
On other machine,the size might be as
follows:
sizeof(char)=1; sizeof(short)=2;
sizeof(int)=2; sizeof(long)=4;
7
The only guarantees made by
C++ are,,,
1 = sizeof( char ) <= sizeof( short ) <= sizeof( int ) <= sizeof( long )
1 <= sizeof ( bool ) <= sizeof ( long )
sizeof ( float ) <= sizeof ( double ) <= sizeof ( long double )
char is at least 8 bits
short is at least 16 bits
long is at least 32 bits
8
Using one byte ( = 8 bits ),
HOW MANY DIFFERENT NUMBERS CAN BE
REPRESENTED USING 0?s and 1?s?
Each bit can hold either a 0 or a 1,So there are just
two choices for each bit,and there are 8 bits.
2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 28 = 256
0 1 1 0 0 0 1 1
9
Similarly,
using two bytes ( = 16 bits),
216 = 65,536
DIFFERENT NUMBERS CAN BE REPRESENTED.
If we wish to have only one number representing the
integer zero,and half of the remaining numbers positive,
and half negative,we can obtain the 65,536 numbers in
the range below,
-32,768,,,,0,,,,32,767
0 1 0 0 1 0 1 00 1 1 0 0 0 1 1
10
Range of Values
The interval within which values of a
numeric type must fall,specified in terms
of the largest and smallest allowable
values,
11
Some Integral Types
Type Size in Bytes Minimum Value Maximum Value
char 1 -128 127
short 2 -32,768 32,767
int 2 -32,768 32,767
long 4 -2,147,483,648 2,147,483,647
NOTE,Values given for one machine,Actual sizes are machine-dependent.
12
Data Type bool
domain contains only 2 values,true and false
allowable operation are the logical ( !,&&,||)
and relational operations
13
Exponential (Scientific) Notation
2.7E4 means 2.7 x 10 4 =
2.7000 =
27000.0
2.7E-4 means 2.7 x 10 - 4 =
0002.7 =
0.00027
14
Floating Point Types
Type Size in Bytes Minimum Maximum
Positive Value Positive Value
float 4 3.4E-38 3.4E+38
double 8 1.7E-308 1.7E+308
long double 10 3.4E-4932 1.1E+4932
NOTE,Values given for one machine,Actual sizes are machine-dependent.
15
More about Floating Point Types
floating point constants in C++ like 94.6 without a
suffix are of type double by default
to obtain another floating point type constant a
suffix must be used
the suffix F or f denotes float type,as in 94.6F
the suffix L or l denotes long double,as in 94.6L
16
Header Files
climits and cfloat
contain constants whose values are the
maximum and minimum for your machine
such constants are FLT_MAX,FLT_MIN,
LONG_MAX,LONG_MIN
#include < climits >
using namespace std ;
.
.
.
cout <<,Maximum long is,<< LONG_MAX << endl ;
cout <<,Minimum long is,<< LONG_MIN << endl ;
17
Assignment Expressions
Assignment expression:
A C++ expression with
(1) a value and
(2) the side effect of storing the expression
value into a memory location.
Example,delta = 2*12
Expression statement,a statement formed b
appending a semicolon to an expression.
Example,delta = 2*12 ;
18
C++ Has Combined Assignment
Operators
int age ;
cin >> age ;
Write a statement to add 3 to age.
age = age + 3 ;
OR,
age += 3 ;
19
Write a statement to subtract 10 from
weight
int weight ;
cin >> weight ;
weight = weight - 10 ;
OR,
weight -= 10 ;
20
Write a statement to divide money by 5.0
float money ;
cin >> money ;
money = money / 5.0 ;
OR,
money /= 5.0 ;
21
Write a statement to double profits
float profits ;
cin >> profits ;
profits = profits * 2.0 ;
OR,
profits *= 2.0 ;
22
Write a statement to raise cost 15%
float cost;
cin >> cost;
cost = cost + cost *,15 ;
OR,
cost = 1.15 * cost;
OR,
cost *= 1.15 ;
23
Which form to use?
when the increment (or decrement)
operator is used in a,stand alone”
statement solely to add one (or subtract
one) from a variable?s value,it can be used
in either prefix or postfix form
dogs-- ; --dogs;
USE EITHER
24
BUT...
when the increment (or decrement)
operator is used in a statement with
other operators,the prefix and
postfix forms can yield different
results
LET?S SEE HOW.,,
25
num
num alpha
alpha
num
int alpha ;
int num ;
num = 13;
alpha = num++ * 3;
13
13 39
14
POSTFIX FORM
“Use,then increment”
26
int alpha ;
int num ;
num = 13;
alpha = ++num * 3;
13
num
14
num alpha
alpha
4214
num
PREFIX FORM
“First increment,then use,
27
Bitwise Operators
The bitwise operators are used for
manipulating individual bits within a memory
cell.
Bitwise Operators:
<< Lift shift
>> Right shift
& Bitwise AND
| Bitwise OR
^ Bitwise EXCLUSIVE OR
~ Complement(invert all bits)
28
Type Cast Operator
The C++ cast operator is used to explicitly request a
type conversion,The cast operation has two forms.
int intVar;
float floatVar = 104.8 ;
intVar = int ( floatVar ) ; // functional notation,OR
intVar = ( int ) floatVar ; // prefix notation uses ( )
104.8 104
floatVar intVar
29
Operator sizeof
DEFINITION
C++ has a unary operator named sizeof that yields the
size on your machine,in bytes,of its single operand,
The operand can be a variable name,or it can be the
name of a data type enclosed in parentheses.
int age ;
cout <<,Size in bytes of variable age is,<< sizeof age << endl ;
cout <<,Size in bytes of type float is,<< sizeof ( float ) << endl ;
30
SYNTAX
Expression1? Expression2,Expression3
MEANING
If Expression1 is true (nonzero),then the value of the
entire expression is Expression2,Otherwise,the
value of the entire expression is Expression 3.
FOR EXAMPLE,,,
Ternary (three-operand) Operator
,
31
Using Conditional Operator
float Smaller ( float x,float y )
// Finds the smaller of two float values
// Precondition,x assigned && y assigned
// Postcondition,Function value == x,if x < y
// == y,otherwise
{
float min;
min = ( x < y )? x,y ;
return min ;
}
32
C++ Operator Precedence
(highest to lowest)
Operator Associativity
( ) Left to right
unary,++ -- ! + - (cast) sizeof Right to left
* / % Left to right
+ - Left to right
< <= > >= Left to right
== != Left to right
&& Left to right
|| Left to right
,Right to left
= += -= *= /= Right to left
33
C++ Data Types
structured
array struct union class
address
pointer reference
simple
integral enum
char short int long bool
floating
float double long double
34
ASCII and EBCDIC
ASCII (pronounced ask-key) and EBCDIC are
the two character sets commonly used to
represent characters internally as integers
ASCII is used on most personal computers,and
EBCDIC is used mainly on IBM mainframes
using ASCII the character?A? is internally stored
as integer 65,Using EBCDIC the?A? is stored as
193,In both sets,the successive alphabet
letters are stored as successive integers,This
enables character comparisons with?A? less
than?B?,etc.
Character Sets
35
Each character has an external
representation and an internal
representation
External representation,the printable
(character) form of a data value.
Internal representation,the form in
which a data value is stored inside the
memory unit.
36
Left
Digit(s)
3? !,# $ % &?
4 ( ) * +,-,/ 0 1
5 2 3 4 5 6 7 8 9,;
6 < = >? @ A B C D E
7 F G H I J K L M N O
8 P Q R S T U V W X Y
9 Z [ \ ] ^ _ ` a b c
10 d e f g h I j k l m
11 n o p q r s t u v w
12 x y z { | } ~
Right
Digit
ASCII (Printable) Character Set
0 1 2 3 4 5 6 7 8 9
37
Incrementing char Variable
because char variables are stored internally
as integers,they can be incremented and
compared
EXAMPLE
char ch;
// loop to print out letters A thru Z
for (ch =?A? ; ch <=?Z? ; ch++ )
{
cout << ch ;
}
38
Control Characters
in addition to the printable characters,character
sets also have nonprintable control characters to
control the screen,printer,and other hardware
in C++ programs,control characters are
represented by escape sequences,Each escape
sequence is formed by a backslash followed by
one or more additional characters
39
Some Escape Sequences
\n Newline (Line feed in ASCII)
\t Horizontal tab
\b Backspace
\a Alert (bell or beep)
\\ Backslash
\? Single quote (apostrophe)
\” Double quote (quotation mark)
\0 Null character (all zero bits)
\ddd Octal equivalent (3 octal digits)
\xdd Hexadecimal equivalent (1 or more
hex digits for integer value of character)
40
Comparing Characters
Characters can be compared b using
<,<=,>,>=.
Example
If the variable firstletter contains the first
letter of a person’s last name,we can test to
see if the last name starts with A through H by
using this test:
if (firstletter >= ‘A’ && firstletter <= ‘H’)
41
Converting char digit to int
the successive digit characters?0? through?9? are represented
in ASCII by the successive integers 48 through 57 (the situation
is similar in EBCDIC)
as a result,the following expression converts a char digit value
to its corresponding integer value
2
ch number
char ch ;
int number ;
.,,
number = int ( ch -?0? ) ; // using explicit type cast
42
Character Function Prototypes
in < cctype >
int toupper ( int ch );
// FUNCTION VALUE
// == uppercase equivalent of ch,if ch is a lowercase letter
// == ch,otherwise
int tolower ( int ch );
// FUNCTION VALUE
// == lowercase equivalent of ch,if ch is an uppercase letter
// == ch,otherwise
NOTE,Although parameter and return type are int,in concept
these functions operate on character data.
Converting to lowercase and uppercase
43
Reading a Yes or No User Response
String inputStr ;
.
.
.
cout <<,Enter Yes or No” ;
cin >> inputStr ;
if ( toupper ( inputStr [0] ) ==?Y? )
{ // First letter was?Y?
.
.
.
}
else if ( toupper ( inputStr [0] ) ==?N? )
{ // First letter was?N?
.
.
.
}
else
PrintErrorMsg ( ) ;
44
More on Floating-Point
Numbers
Representation of Floating-Point Numbers
When a float variable or constant is defined,
the number stored there has both a whole
number part and a fractional part,so it must be
coded to represent both parts.
Precision,the maximum number of significant
digits.
Significant digits,those digits from the first
nonzero digit on the left to the last nonzero
digit on the right (plus any 0 digits that are
exact).
45
Arithmetic with Floating-Point
Numbers
Floating-Point arithmetic is seldom
exact.
Representational error,arithmetic error
that occurs when the precision of the
true result of an arithmetic operation is
greater than the precision of the
machine.
Underflow and overflow
46
typedef statement
typedef creates an additional name for an
already existing data type
before bool type became part of ISO-ANSI C++,
a Boolean type was simulated this way
typedef int Boolean;
const Boolean true = 1 ;
const Boolean false = 0 ;
.
.
.
Boolean dataOK ;
.
.
.
dataOK = true ;
User-Defined Simple Types
47
Enumeration Types
Enumeration type,a user-defined data
type whose domain is an order set of
literal values expressed as identifiers.
Enumerator,one of the values in the
domain of an enumeration type.
48
Enumeration Types (cont.)
C++ allows creation of a new simple type by
listing (enumerating) all the ordered values in
the domain of the type
EXAMPLE
enum MonthType { JAN,FEB,MAR,APR,MAY,JUN,
JUL,AUG,SEP,OCT,NOV,DEC } ;
name of new type list of all possible values of this new type
49
enum Type Declaration
enum MonthType { JAN,FEB,MAR,APR,MAY,JUN,
JUL,AUG,SEP,OCT,NOV,DEC } ;
the enum declaration creates a new programmer-
defined type and lists all the possible values of that
type--any valid C++ identifiers can be used as values
the listed values are ordered as listed,That is,JAN <
FEB < MAR < APR,and so on
you must still declare variables of this type
50
Declaring enum Type Variables
enum MonthType { JAN,FEB,MAR,APR,MAY,JUN,
JUL,AUG,SEP,OCT,NOV,DEC } ;
MonthType thisMonth; // declares 2 variables
MonthType lastMonth; // of type MonthType
lastMonth = OCT ; // assigns values
thisMonth = NOV ; // to these variables
.
.
.
lastMonth = thisMonth ;
thisMonth = DEC ;
51
Storage of enum Type Variables
enum MonthType { JAN,FEB,MAR,APR,MAY,JUN,
JUL,AUG,SEP,OCT,NOV,DEC } ;
stored as 0 stored as 1 stored as 2 stored as 3 etc,
stored as 11
52
Use Type Cast to Increment
enum Type Variables
enum MonthType { JAN,FEB,MAR,APR,MAY,JUN,
JUL,AUG,SEP,OCT,NOV,DEC } ;
MonthType thisMonth;
MonthType lastMonth;
lastMonth = OCT ;
thisMonth = NOV ;
lastMonth = thisMonth ;
thisMonth = thisMonth++ ; // COMPILE ERROR !
thisMonth = MonthType( thisMonth + 1) ; // uses type cast
53
More about enum Type
Enumeration type can be used in a Switch statement
for the switch expression and the case labels.
Stream I/O ( using the insertion << and extraction >>
operators ) is not defined for enumeration types,
Instead,functions can be written for this purpose.
Comparison of enum type values is defined using the
6 relational operators ( <,<=,>,>=,==,!= ).
An enum type can be the return type of a value-
returning function in C++.
SOME EXAMPLES,,,
54
MonthType thisMonth;
switch ( thisMonth ) // using enum type switch expression
{
case JAN,
case FEB,
case MAR,cout <<,Winter quarter” ;
break ;
case APR,
case MAY,
case JUN,cout <<,Spring quarter” ;
break ;
case JUL,
case AUG,
case SEP,cout <<,Summer quarter” ;
break ;
case OCT,
case NOV,
case DEC,cout <<,Fall quarter” ;
}
55
Using enum type Control
Variable with for Loop
enum MonthType { JAN,FEB,MAR,APR,MAY,JUN,
JUL,AUG,SEP,OCT,NOV,DEC } ;
void WriteOutName ( /* in */ MonthType ) ; // prototype
.
,
.
MonthType month ;
for (month = JAN ; month <= DEC ; month = MonthType (month + 1 ) )
{ // requires use of type cast to increment
WriteOutName ( month ) ; // function call to perform output
.
.
.
}
56
void WriteOutName ( /* in */ MonthType month )
// Prints out calendar name corresponding to month
// Precondition,month is assigned
// Postcondition,calendar name for month has been written out
{ switch ( month )
{
case JAN,cout <<,January,; break ;
case FEB,cout <<,February,; break ;
case MAR,cout <<,March,; break ;
case APR,cout <<,April,; break ;
case MAY,cout <<,May,; break ;
case JUN,cout <<,June,; break ;
case JUL,cout <<,July,; break ;
case AUG,cout <<,August,; break ;
case SEP,cout <<,September,; break ;
case OCT,cout <<,October,; break ;
case NOV,cout <<,November,; break ;
case DEC,cout <<,December,; break ;
}
}
57
enum SchoolType { PRE_SCHOOL,ELEM_SCHOOL,
MIDDLE_SCHOOL,HIGH_SCHOOL,COLLEGE } ;
.
.
.
SchoolType GetSchoolData ( void )
// Obtains information from keyboard to determine school level
// Postcondition,Function value == personal school level
{
SchoolType schoolLevel ;
int age ;
int lastGrade ;
cout <<,Enter age,,; // prompt for information
cin >> age ;
Function with enum type
Return Value
58
if ( age < 6 )
schoolLevel = PRE_SCHOOL ;
else
{ cout <<,Enter last grade completed in school,,;
cin >> lastGrade;
if ( lastGrade < 5 )
schoolLevel = ELEM_SCHOOL ;
else if ( lastGrade < 8 )
schoolLevel = MIDDLE_SCHOOL ;
else if ( lastGrade < 12 )
schoolLevel = HIGH_SCHOOL ;
else
schoolLevel = COLLEGE ;
}
return schoolLevel ; // return enum type value
}
59
Named and Anonymous Data
Types
Named type,a user-defined type whose
declaration includes a type identifier that gives
a name to the type.
Anonymous type,a type that does not have
an associated type identifier.
enum {OK,OUT_OF_STOCK,BACK_ORDERED} status;
60
Multifile C++ Programs
C++ programs often consist of several different files
with extensions such as,h and,cpp
related typedef statements,const values,enum type
declarations,and similar items are often placed in
user-written header files
by using the #include preprocessor directive the
contents of these header files are inserted into any
program file that uses them
61
Inserting Header Files
#include <iostream> // iostream
#include,school.h”
int main ( )
{ enum SchoolType
{ PRE_SCHOOL,
,ELEM_SCHOOL,
,MIDDLE_SCHOOL,
,HIGH_SCHOOL,
COLLEGE } ;
}
62
Implicit type coercion occurs,,,
whenever values of different data types are used in:
1,arithmetic and relational expressions
2,assignment operations
3,parameter passage
4,returning a function value with return
(from a value-returning function)
TWO RULES APPLY,,,
63
Promotion (or widening) in C++.,,
is the conversion of a value from a,lower” type to a
“higher” type--specifically,for mixed type expressions:
Step 1,Each char,short,bool,or enumeration value is promoted to
int,If both operands are now int,the result is an int expression.
Step 2,If Step 1 leaves a mixed-type expression,the following
precedence of types is used (from lowest to highest):
int,unsigned int,long,unsigned long,float,double,long double
The value of the operand of,lower” type is promoted to that of the
“higher” type,For an arithmetic expression,the result is an
expression of that higher type,For a relational expression,the
result is always bool (true or false).
64
is the conversion of a value from a,higher” type to a
“lower” type,and may cause loss of information
FOR EXAMPLE,98.6 98
temperature number
float temperature = 98.6 ;
int number ;
number = temperature ; // demotion occurs
Demotion (or narrowing),,,
Simple Data Types,Built-in and
Use-Defined
2
Chapter 10 Topics
Built-In Simple Types
Integral and Floating Point Data Types
Using Combined Assignment Operators
Prefix and Postfix Forms of Increment and
Decrement Operators
Additional C++ Operator
Character Sets
Using an Enumeration Type
Creating and Including User-Written Header Files
3
Built-In Simple Types
Simple(atomic)data type:
A data type in which each value is
atomic(indivisible).
Example,
a single character of type char is atomic,
but the string,Good Morning” is not,
4
C++ Simple Data Types
simple types
integral floating
char short int long bool enum float double long double
unsigned
5
By definition,
the size of a C++ char value is always 1
byte,
exactly one byte of memory space
Sizes of other data type values in C++ are
machine-dependent,
‘ A?
6
Example
On one machine,it maybe the case that
sizeof(char)=1; sizeof(short)=2;
sizeof(int)=4; sizeof(long)=8;
On other machine,the size might be as
follows:
sizeof(char)=1; sizeof(short)=2;
sizeof(int)=2; sizeof(long)=4;
7
The only guarantees made by
C++ are,,,
1 = sizeof( char ) <= sizeof( short ) <= sizeof( int ) <= sizeof( long )
1 <= sizeof ( bool ) <= sizeof ( long )
sizeof ( float ) <= sizeof ( double ) <= sizeof ( long double )
char is at least 8 bits
short is at least 16 bits
long is at least 32 bits
8
Using one byte ( = 8 bits ),
HOW MANY DIFFERENT NUMBERS CAN BE
REPRESENTED USING 0?s and 1?s?
Each bit can hold either a 0 or a 1,So there are just
two choices for each bit,and there are 8 bits.
2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 28 = 256
0 1 1 0 0 0 1 1
9
Similarly,
using two bytes ( = 16 bits),
216 = 65,536
DIFFERENT NUMBERS CAN BE REPRESENTED.
If we wish to have only one number representing the
integer zero,and half of the remaining numbers positive,
and half negative,we can obtain the 65,536 numbers in
the range below,
-32,768,,,,0,,,,32,767
0 1 0 0 1 0 1 00 1 1 0 0 0 1 1
10
Range of Values
The interval within which values of a
numeric type must fall,specified in terms
of the largest and smallest allowable
values,
11
Some Integral Types
Type Size in Bytes Minimum Value Maximum Value
char 1 -128 127
short 2 -32,768 32,767
int 2 -32,768 32,767
long 4 -2,147,483,648 2,147,483,647
NOTE,Values given for one machine,Actual sizes are machine-dependent.
12
Data Type bool
domain contains only 2 values,true and false
allowable operation are the logical ( !,&&,||)
and relational operations
13
Exponential (Scientific) Notation
2.7E4 means 2.7 x 10 4 =
2.7000 =
27000.0
2.7E-4 means 2.7 x 10 - 4 =
0002.7 =
0.00027
14
Floating Point Types
Type Size in Bytes Minimum Maximum
Positive Value Positive Value
float 4 3.4E-38 3.4E+38
double 8 1.7E-308 1.7E+308
long double 10 3.4E-4932 1.1E+4932
NOTE,Values given for one machine,Actual sizes are machine-dependent.
15
More about Floating Point Types
floating point constants in C++ like 94.6 without a
suffix are of type double by default
to obtain another floating point type constant a
suffix must be used
the suffix F or f denotes float type,as in 94.6F
the suffix L or l denotes long double,as in 94.6L
16
Header Files
climits and cfloat
contain constants whose values are the
maximum and minimum for your machine
such constants are FLT_MAX,FLT_MIN,
LONG_MAX,LONG_MIN
#include < climits >
using namespace std ;
.
.
.
cout <<,Maximum long is,<< LONG_MAX << endl ;
cout <<,Minimum long is,<< LONG_MIN << endl ;
17
Assignment Expressions
Assignment expression:
A C++ expression with
(1) a value and
(2) the side effect of storing the expression
value into a memory location.
Example,delta = 2*12
Expression statement,a statement formed b
appending a semicolon to an expression.
Example,delta = 2*12 ;
18
C++ Has Combined Assignment
Operators
int age ;
cin >> age ;
Write a statement to add 3 to age.
age = age + 3 ;
OR,
age += 3 ;
19
Write a statement to subtract 10 from
weight
int weight ;
cin >> weight ;
weight = weight - 10 ;
OR,
weight -= 10 ;
20
Write a statement to divide money by 5.0
float money ;
cin >> money ;
money = money / 5.0 ;
OR,
money /= 5.0 ;
21
Write a statement to double profits
float profits ;
cin >> profits ;
profits = profits * 2.0 ;
OR,
profits *= 2.0 ;
22
Write a statement to raise cost 15%
float cost;
cin >> cost;
cost = cost + cost *,15 ;
OR,
cost = 1.15 * cost;
OR,
cost *= 1.15 ;
23
Which form to use?
when the increment (or decrement)
operator is used in a,stand alone”
statement solely to add one (or subtract
one) from a variable?s value,it can be used
in either prefix or postfix form
dogs-- ; --dogs;
USE EITHER
24
BUT...
when the increment (or decrement)
operator is used in a statement with
other operators,the prefix and
postfix forms can yield different
results
LET?S SEE HOW.,,
25
num
num alpha
alpha
num
int alpha ;
int num ;
num = 13;
alpha = num++ * 3;
13
13 39
14
POSTFIX FORM
“Use,then increment”
26
int alpha ;
int num ;
num = 13;
alpha = ++num * 3;
13
num
14
num alpha
alpha
4214
num
PREFIX FORM
“First increment,then use,
27
Bitwise Operators
The bitwise operators are used for
manipulating individual bits within a memory
cell.
Bitwise Operators:
<< Lift shift
>> Right shift
& Bitwise AND
| Bitwise OR
^ Bitwise EXCLUSIVE OR
~ Complement(invert all bits)
28
Type Cast Operator
The C++ cast operator is used to explicitly request a
type conversion,The cast operation has two forms.
int intVar;
float floatVar = 104.8 ;
intVar = int ( floatVar ) ; // functional notation,OR
intVar = ( int ) floatVar ; // prefix notation uses ( )
104.8 104
floatVar intVar
29
Operator sizeof
DEFINITION
C++ has a unary operator named sizeof that yields the
size on your machine,in bytes,of its single operand,
The operand can be a variable name,or it can be the
name of a data type enclosed in parentheses.
int age ;
cout <<,Size in bytes of variable age is,<< sizeof age << endl ;
cout <<,Size in bytes of type float is,<< sizeof ( float ) << endl ;
30
SYNTAX
Expression1? Expression2,Expression3
MEANING
If Expression1 is true (nonzero),then the value of the
entire expression is Expression2,Otherwise,the
value of the entire expression is Expression 3.
FOR EXAMPLE,,,
Ternary (three-operand) Operator
,
31
Using Conditional Operator
float Smaller ( float x,float y )
// Finds the smaller of two float values
// Precondition,x assigned && y assigned
// Postcondition,Function value == x,if x < y
// == y,otherwise
{
float min;
min = ( x < y )? x,y ;
return min ;
}
32
C++ Operator Precedence
(highest to lowest)
Operator Associativity
( ) Left to right
unary,++ -- ! + - (cast) sizeof Right to left
* / % Left to right
+ - Left to right
< <= > >= Left to right
== != Left to right
&& Left to right
|| Left to right
,Right to left
= += -= *= /= Right to left
33
C++ Data Types
structured
array struct union class
address
pointer reference
simple
integral enum
char short int long bool
floating
float double long double
34
ASCII and EBCDIC
ASCII (pronounced ask-key) and EBCDIC are
the two character sets commonly used to
represent characters internally as integers
ASCII is used on most personal computers,and
EBCDIC is used mainly on IBM mainframes
using ASCII the character?A? is internally stored
as integer 65,Using EBCDIC the?A? is stored as
193,In both sets,the successive alphabet
letters are stored as successive integers,This
enables character comparisons with?A? less
than?B?,etc.
Character Sets
35
Each character has an external
representation and an internal
representation
External representation,the printable
(character) form of a data value.
Internal representation,the form in
which a data value is stored inside the
memory unit.
36
Left
Digit(s)
3? !,# $ % &?
4 ( ) * +,-,/ 0 1
5 2 3 4 5 6 7 8 9,;
6 < = >? @ A B C D E
7 F G H I J K L M N O
8 P Q R S T U V W X Y
9 Z [ \ ] ^ _ ` a b c
10 d e f g h I j k l m
11 n o p q r s t u v w
12 x y z { | } ~
Right
Digit
ASCII (Printable) Character Set
0 1 2 3 4 5 6 7 8 9
37
Incrementing char Variable
because char variables are stored internally
as integers,they can be incremented and
compared
EXAMPLE
char ch;
// loop to print out letters A thru Z
for (ch =?A? ; ch <=?Z? ; ch++ )
{
cout << ch ;
}
38
Control Characters
in addition to the printable characters,character
sets also have nonprintable control characters to
control the screen,printer,and other hardware
in C++ programs,control characters are
represented by escape sequences,Each escape
sequence is formed by a backslash followed by
one or more additional characters
39
Some Escape Sequences
\n Newline (Line feed in ASCII)
\t Horizontal tab
\b Backspace
\a Alert (bell or beep)
\\ Backslash
\? Single quote (apostrophe)
\” Double quote (quotation mark)
\0 Null character (all zero bits)
\ddd Octal equivalent (3 octal digits)
\xdd Hexadecimal equivalent (1 or more
hex digits for integer value of character)
40
Comparing Characters
Characters can be compared b using
<,<=,>,>=.
Example
If the variable firstletter contains the first
letter of a person’s last name,we can test to
see if the last name starts with A through H by
using this test:
if (firstletter >= ‘A’ && firstletter <= ‘H’)
41
Converting char digit to int
the successive digit characters?0? through?9? are represented
in ASCII by the successive integers 48 through 57 (the situation
is similar in EBCDIC)
as a result,the following expression converts a char digit value
to its corresponding integer value
2
ch number
char ch ;
int number ;
.,,
number = int ( ch -?0? ) ; // using explicit type cast
42
Character Function Prototypes
in < cctype >
int toupper ( int ch );
// FUNCTION VALUE
// == uppercase equivalent of ch,if ch is a lowercase letter
// == ch,otherwise
int tolower ( int ch );
// FUNCTION VALUE
// == lowercase equivalent of ch,if ch is an uppercase letter
// == ch,otherwise
NOTE,Although parameter and return type are int,in concept
these functions operate on character data.
Converting to lowercase and uppercase
43
Reading a Yes or No User Response
String inputStr ;
.
.
.
cout <<,Enter Yes or No” ;
cin >> inputStr ;
if ( toupper ( inputStr [0] ) ==?Y? )
{ // First letter was?Y?
.
.
.
}
else if ( toupper ( inputStr [0] ) ==?N? )
{ // First letter was?N?
.
.
.
}
else
PrintErrorMsg ( ) ;
44
More on Floating-Point
Numbers
Representation of Floating-Point Numbers
When a float variable or constant is defined,
the number stored there has both a whole
number part and a fractional part,so it must be
coded to represent both parts.
Precision,the maximum number of significant
digits.
Significant digits,those digits from the first
nonzero digit on the left to the last nonzero
digit on the right (plus any 0 digits that are
exact).
45
Arithmetic with Floating-Point
Numbers
Floating-Point arithmetic is seldom
exact.
Representational error,arithmetic error
that occurs when the precision of the
true result of an arithmetic operation is
greater than the precision of the
machine.
Underflow and overflow
46
typedef statement
typedef creates an additional name for an
already existing data type
before bool type became part of ISO-ANSI C++,
a Boolean type was simulated this way
typedef int Boolean;
const Boolean true = 1 ;
const Boolean false = 0 ;
.
.
.
Boolean dataOK ;
.
.
.
dataOK = true ;
User-Defined Simple Types
47
Enumeration Types
Enumeration type,a user-defined data
type whose domain is an order set of
literal values expressed as identifiers.
Enumerator,one of the values in the
domain of an enumeration type.
48
Enumeration Types (cont.)
C++ allows creation of a new simple type by
listing (enumerating) all the ordered values in
the domain of the type
EXAMPLE
enum MonthType { JAN,FEB,MAR,APR,MAY,JUN,
JUL,AUG,SEP,OCT,NOV,DEC } ;
name of new type list of all possible values of this new type
49
enum Type Declaration
enum MonthType { JAN,FEB,MAR,APR,MAY,JUN,
JUL,AUG,SEP,OCT,NOV,DEC } ;
the enum declaration creates a new programmer-
defined type and lists all the possible values of that
type--any valid C++ identifiers can be used as values
the listed values are ordered as listed,That is,JAN <
FEB < MAR < APR,and so on
you must still declare variables of this type
50
Declaring enum Type Variables
enum MonthType { JAN,FEB,MAR,APR,MAY,JUN,
JUL,AUG,SEP,OCT,NOV,DEC } ;
MonthType thisMonth; // declares 2 variables
MonthType lastMonth; // of type MonthType
lastMonth = OCT ; // assigns values
thisMonth = NOV ; // to these variables
.
.
.
lastMonth = thisMonth ;
thisMonth = DEC ;
51
Storage of enum Type Variables
enum MonthType { JAN,FEB,MAR,APR,MAY,JUN,
JUL,AUG,SEP,OCT,NOV,DEC } ;
stored as 0 stored as 1 stored as 2 stored as 3 etc,
stored as 11
52
Use Type Cast to Increment
enum Type Variables
enum MonthType { JAN,FEB,MAR,APR,MAY,JUN,
JUL,AUG,SEP,OCT,NOV,DEC } ;
MonthType thisMonth;
MonthType lastMonth;
lastMonth = OCT ;
thisMonth = NOV ;
lastMonth = thisMonth ;
thisMonth = thisMonth++ ; // COMPILE ERROR !
thisMonth = MonthType( thisMonth + 1) ; // uses type cast
53
More about enum Type
Enumeration type can be used in a Switch statement
for the switch expression and the case labels.
Stream I/O ( using the insertion << and extraction >>
operators ) is not defined for enumeration types,
Instead,functions can be written for this purpose.
Comparison of enum type values is defined using the
6 relational operators ( <,<=,>,>=,==,!= ).
An enum type can be the return type of a value-
returning function in C++.
SOME EXAMPLES,,,
54
MonthType thisMonth;
switch ( thisMonth ) // using enum type switch expression
{
case JAN,
case FEB,
case MAR,cout <<,Winter quarter” ;
break ;
case APR,
case MAY,
case JUN,cout <<,Spring quarter” ;
break ;
case JUL,
case AUG,
case SEP,cout <<,Summer quarter” ;
break ;
case OCT,
case NOV,
case DEC,cout <<,Fall quarter” ;
}
55
Using enum type Control
Variable with for Loop
enum MonthType { JAN,FEB,MAR,APR,MAY,JUN,
JUL,AUG,SEP,OCT,NOV,DEC } ;
void WriteOutName ( /* in */ MonthType ) ; // prototype
.
,
.
MonthType month ;
for (month = JAN ; month <= DEC ; month = MonthType (month + 1 ) )
{ // requires use of type cast to increment
WriteOutName ( month ) ; // function call to perform output
.
.
.
}
56
void WriteOutName ( /* in */ MonthType month )
// Prints out calendar name corresponding to month
// Precondition,month is assigned
// Postcondition,calendar name for month has been written out
{ switch ( month )
{
case JAN,cout <<,January,; break ;
case FEB,cout <<,February,; break ;
case MAR,cout <<,March,; break ;
case APR,cout <<,April,; break ;
case MAY,cout <<,May,; break ;
case JUN,cout <<,June,; break ;
case JUL,cout <<,July,; break ;
case AUG,cout <<,August,; break ;
case SEP,cout <<,September,; break ;
case OCT,cout <<,October,; break ;
case NOV,cout <<,November,; break ;
case DEC,cout <<,December,; break ;
}
}
57
enum SchoolType { PRE_SCHOOL,ELEM_SCHOOL,
MIDDLE_SCHOOL,HIGH_SCHOOL,COLLEGE } ;
.
.
.
SchoolType GetSchoolData ( void )
// Obtains information from keyboard to determine school level
// Postcondition,Function value == personal school level
{
SchoolType schoolLevel ;
int age ;
int lastGrade ;
cout <<,Enter age,,; // prompt for information
cin >> age ;
Function with enum type
Return Value
58
if ( age < 6 )
schoolLevel = PRE_SCHOOL ;
else
{ cout <<,Enter last grade completed in school,,;
cin >> lastGrade;
if ( lastGrade < 5 )
schoolLevel = ELEM_SCHOOL ;
else if ( lastGrade < 8 )
schoolLevel = MIDDLE_SCHOOL ;
else if ( lastGrade < 12 )
schoolLevel = HIGH_SCHOOL ;
else
schoolLevel = COLLEGE ;
}
return schoolLevel ; // return enum type value
}
59
Named and Anonymous Data
Types
Named type,a user-defined type whose
declaration includes a type identifier that gives
a name to the type.
Anonymous type,a type that does not have
an associated type identifier.
enum {OK,OUT_OF_STOCK,BACK_ORDERED} status;
60
Multifile C++ Programs
C++ programs often consist of several different files
with extensions such as,h and,cpp
related typedef statements,const values,enum type
declarations,and similar items are often placed in
user-written header files
by using the #include preprocessor directive the
contents of these header files are inserted into any
program file that uses them
61
Inserting Header Files
#include <iostream> // iostream
#include,school.h”
int main ( )
{ enum SchoolType
{ PRE_SCHOOL,
,ELEM_SCHOOL,
,MIDDLE_SCHOOL,
,HIGH_SCHOOL,
COLLEGE } ;
}
62
Implicit type coercion occurs,,,
whenever values of different data types are used in:
1,arithmetic and relational expressions
2,assignment operations
3,parameter passage
4,returning a function value with return
(from a value-returning function)
TWO RULES APPLY,,,
63
Promotion (or widening) in C++.,,
is the conversion of a value from a,lower” type to a
“higher” type--specifically,for mixed type expressions:
Step 1,Each char,short,bool,or enumeration value is promoted to
int,If both operands are now int,the result is an int expression.
Step 2,If Step 1 leaves a mixed-type expression,the following
precedence of types is used (from lowest to highest):
int,unsigned int,long,unsigned long,float,double,long double
The value of the operand of,lower” type is promoted to that of the
“higher” type,For an arithmetic expression,the result is an
expression of that higher type,For a relational expression,the
result is always bool (true or false).
64
is the conversion of a value from a,higher” type to a
“lower” type,and may cause loss of information
FOR EXAMPLE,98.6 98
temperature number
float temperature = 98.6 ;
int number ;
number = temperature ; // demotion occurs
Demotion (or narrowing),,,
