Introduction_to_c++_programming

Introduction To C++ Programming Language

LECTURE

What is C++ C++ is a high-level language and it is evolved from C over a period of several years starting in 1980.  The standard for C++ was jointly developed by the American National Standards Institute (ANSI) and the International Standards Organization (ISO).  a set of rules, symbols, and special words used to construct a computer 

Structure of a C++ Program

Figure 3.1 Structure of a C++ Program

A Typical C++ Program // A typical C++ Program

Comment

# include

using namespace std; # define PI 3.142

Preprocessor Directive

int

Global Declaration

Integer;

int main ( ) { double radius, area; radius = 7; area = radius * radius * PI; return 0; }

Local declaration

Statements

Main function

Character Set C++ is composed of character set :





Number : 0 to 9



Alphabetical : a to z and A to Z



Spacing



Special Character : 

, . : ; ? ! ( ) {} “ ‘ + - * / = > < # % & ^ ~ | / _

Token 

Token : combination of the characters in C++



Categorised into: 

Identifiers



Reserved words/keywords



Constants



Literal String



Punctuators



Operators

Identifiers 







Allows programmers to name data and other objects in the program-variable, constant, function etc. Can use any capital letter A through Z, lowercase letters a through z, digits 0 through 9 and also underscore ( _ ) Rules for identifier  The first character must be alphabetic character or underscore  It must consists only of alphabetic characters, digits and underscores, cannot contain spaces  It cannot duplicate any reserved word C++ is case-sensitive; this means that CASE, Case, case, and CaSe are four completely different words.

Valid and Invalid Identifiers Valid names A  student_name  _aSystemNam e  pi  al  stdntNm  _anthrSysNm  PI 

Invalid names  $sum

// $ is illegal  2names // can’t start with 2  stdnt Nmbr // can’t have space  int // reserved word

Reserved word/Keywords A word that has special meaning in C++.  Keywords cannot be used to name identifiers. 

Constant Data values that cannot be changed during the execution of a program  Types of constant: 

Literals constant  Defined constants  Declared constants 

Literals Constant 

If the data cannot be changed, we can simply code the data value itself in a statement Eg: discount = 0.10 ;



Categorised into:

0.10 is a literal constant

Integer Numerals ( eg: 178, -9, 0113, 0x4b)  Floating-Point Numerals (eg: 3.14159,6.02e23,1.6e-19 ,3.0  Characters ( eg: ‘A’, ‘p’)  Strings ( eg; “Hello World”)  Boolean (eg: true , false). 

Defined Constant (#define) 

Use the #define preprocessor directive Format: #define identifier value  Eg : #define EPF_RATE 0.11



Placed at the beginning of the program



#include

using namespace std; #define EPF_RATE 3.142 int main() { ……; nett = salary – ( salary * EPF_RATE); ………; }

Declared Constants se a type const qualifier to indicate that data cannot be changed and to fix the contents of the memory location #include g: const float = 3.1416; using namespace std; #define EPF_RATE 3.142

eclared inside a function

int main() { const double socso_rate = 0.05; nett = salary – ( salary * EPF_RATE * socso_rate); ………; }

Data Types in C++ 

Type defines a set of value and operations that can be applied on those values



Set of values for each type is known as the domain for the type



Functions also have types which is determined by the data it returns

Data Types 





Standard

They serves as the basic building blocks for derived types (complex structures that are built using the standard types

Serves as the basic building blocks for derived types

Data Types 

Derived

Data Type : Void    

Typed as void Has no values and operations Both set of values are empty Usually used in functions  Eg:

void printSum()

Data Type : Char 

 

Used to hold characters or very small integer values Usually 1 byte of memory CODE: char letter; letter = 'C';

Data Type : Integer   

Coded as int A number without a fraction part C++ supports three different sizes of integer  short

int

 int  long 

int

Can be signed and unsigned

Data Type : Integer Maximum Value

Type

Byte Size

Minimum Value

short int

2

-32,768

32,767

unsigned short int

2

0

65,535

int

4

-2,147,483,648

2,147,483,647

unsigned int

4

0

4,294,967,295

long int

4

-2,147,483,648

2,147,483,647

unsigned long int

4

0

4,294,967,295

Data Type : Float  

 

A number with fractional part such as 43.32, - 2.33 C++ supports three types of float  float  double  long float Stored in a form similar to scientific notation Can be represented in  Fixed point (decimal) notation: 31.4159 0.0000625  E notation: 3.14159E1 6.25e-5

Data Type Float 

Are double by default Can be forced to be float (3.14159f) or long double (0.0000625L)



All floating-point numbers are signed



Range

Type

Byte Size

Precision

float

4

7

10-37 ..1038

double

8

15

10-307 ..10308

long double

8

15

10-307 ..10308

Data Type : Boolean 

Represents values that are true or false



bool variables are stored as small integers



false is represented by 0, true by 1: bool allDone = true; bool finished = false; allDone finished

0

Variables 

 

A storage location in memory whose contents can change while program is running Has an identifier and a type of data it can hold Variable declaration syntax :

type identifier [= initial_value] eg : int itemsOrdered;



To hold the number of items ordered.

A variable name should represent the purpose of the variable.

Variables

Variables Initialization 

To initialize a variable means to assign it a value when it is declared: int length = 12;



Can initialize some or all variables: int length = 12, width = 5, area;

Variables Assignment 







An assignment statement uses the = operator to store a value in a variable. item = 12; This statement assigns the value 12 to the item variable. The variable receiving the value must appear on the left side of the = operator. This will NOT work: // ERROR! 12 = item;

Variables Scope 

The scope of a variable: the part of the program in which the variable can be accessed



A variable cannot be used before it is defined

Variables Scope

Global Variables

Local Variable

Local Variable

Variables Scope 

Global scope a global variable is a variable declared in the main body of the source code, outside all functions  Global variables can be referred from anywhere in the code, even inside functions, whenever it is after its declaration. 



Local Scope a

local variable is one declared within the body of a function or a block.  is limited to the block enclosed in braces ({}) where they are declared.

Operators 



C ++ uses a set of built in operators ( Eg : +, -, / etc). Four classes of operators : Arithmetic  Relational  Logical  Assignment 

Arithmetic Operators 

Assume int a=4, b= 5, d; C++ Operation

Arithmetic Operator

C++ Expression

Value of d after assignment

Addition

+

d=a+b

9

Substraction

-

d=b-2

3

Multiplication

*

d=a*b

20

Division

/

d = a/2

2

Modulus

%

d = b%3

2

Assignment Operators 

Assume x=4, y=5, z=8; Assignment Operator

Sample Expression

Similar Expression

Value of variable after assignment

+=

x += 5

x=x+5

x=9

-=

y -= x

y=y-x

y=1

*=

x *= z

x = x*z

x=32

/=

z /=2

z = z/2

z=4

y = y%x

y=1

%=

y %=x

Relational & Equality Operators 

Assume y = 6, x =5 Relational Operators

Sample Expression

Value

>

y>x

T

<

y<2

F

>=

x >= 3

T

<=

y <= x

F

Equality Operators

Sample Expression

Value

==

x == 5

T

!=

y !=6

F

Logical Operators Logical Operators

Called

Sample Operation

&&

AND

expression1 && expression 2

||

OR

expression1 | | expression2

!

NOT

!expression

Example :Assume int x = 50 expression

!expression

Sample Expression

F

T

!(x == 60)

T

F

!(x != 60)

Logical Operators 

Assume x=4, y=5, z=8 Sample Expression

expression1

expression2

expression1 && expression2

F

F

F

( y > 10) && ( z <=x )

F

T

F

( z <= y) && ( x == 4)

T

F

F

( y != z) && ( z < x )

T

T

T

( z >= y ) && ( x != 3 )

Increment and Decrement Operators Operator

Called

Sample Expression

Similar Expression

Explanation

++

preincrement

++a

a = a +1

Increment a by 1, then use the new value of a in expression in which a reside

a += 1 ++

postincrement

a++

a = a +1 a += 1

--

predecrement

--a

a = a -1 a -= 1

--

postdecrement

a--

a = a -1 a -= 1

Use the current value of a in the expression which a reside, then increment a by 1 Decrement a by 1, then use the new value of a in expression in which a reside Use the current value of a in the expression which a reside, then decrement a by 1

Operator Precedence Operators

Associative

()

Left to right

++ - - + - !

Right to left

* / %

Left to right

+ -

Left to right

< <= > >=

Left to right

= = !=

Left to right

&&

Left to right

||

Left to right

*= += - = /= %=

Right to left

Operator Precedence Example 1:

Example 2:

int a=10, b=20, c=15, d=8;

int a=15, b=6, c=5, d=4;

a*b/(-c*31%13)*d

d *= ++b – a/3 + c

1.

a*b/(-15*31%13)*d

1. d *= ++b – a/3+ c

2.

a*b/(-465%13)*d

2. d*=7- a/3+c

3.

a*b/(-10)*d

3. d*=7- 5+c

4.

200/(-10)*d

4. d*=2 + c

5.

-20*d

5. d*= 7

6.

-160

6. d = d*7 7. d = 28

Example of a program // Operating with variables #include using namespace std; int main() { //variables declaration int no1; int no2; int value_div; int value_mod; cout << “Enter two integral numbers:”; cin >> no1 >> no2; value_div= no1 / no2; cout << no1 << “ / ” << no2 << “ is ” << value_div; value_mod = no1 % no2; cout << “ with a remainder of ” << value_mod << endl; return 0; }

Output : Enter two integral numbers : 10 6 10 / 6 is 1 with a remainder of 4

/*Evaluate two complex expression*/ #include using namespace std; void main ( ) { int a =3, b=4, c = 5, x, y; cout << “Initial values of the variables:\n”; cout << “a = “ << a<< “ b = “ << b <<“ c = “ << c<< endl; cout << endl;

Output : Initial values of the variables : a=3

b=4 c= 5

x = a * 4 + b / 2 – c * b; cout << “Value of a * 4 + b/2-c * b is : “ << x << endl; y = - - a * (3 + b) / 2 – c++ * b;

Values of the variables are now :

cout << “Value of - - a * (3 + b) / 2 – c++ * b is: “

a=2

<< y << endl; cout << “a = “ << a << “ b = “ << b << “ c = “ << c << endl; }

Value of a * 4 + b/2-c * b is : -6 Value of - - a * (3 + b) / 2 – c++ * b is: -13

b=4 c= 6

Formatting Output 



Output is made more readable using manipulator

Must include header file. Manipulators endl dec oct hex fixed showpoint setw(…) setprecision setfill(…)

Use New line Formats output as decimal Formats output as octal Formats output as hexadecimal Set floating-point decimals Shows decimal in floating-point values Sets width of output fields Specifies number of decimals for floating point Specifies fill character

Formatting Output 

Set Width (setw) Set the minimum width for an output  Two alignment : right justified and left justified 



Set Fill Character (setfill)  If

the output width is greater than the data values placed in it, a fill character can be used to fill the empty spaces whenever required

Formatting Output 

Three integer manipulators:  Decimal

(dec)

 The

default  Value in decimal form 

Octal (oct)  Values

are displayed in octal numbering system

 Hexadecimal  Values

(hex)

are in hexadecimal format

Formatting Output  

Three Floating-point manipulators: Fixed (fixed) 



Displays floating-point numbers (eg: 1.234568e+6) in the fixed-point format (1234567.875)

Set precision (setprecision)  Used

to control the number of the decimal places to be displayed



Showpoint (showpoint)  To

show value with the decimal point

//demonstrate the output manipulator #include #include using namespace std; int main( ) { char aChar; int integer; float dlrAmnt;

Output : cout << “Please enter an integer ,\n”; << “ a dollar amount and a character.\n”; cin >> integer>>dlrAmnt >> aChar;

cout <<“\nThank you.You entered:\n”; cout << setw( 6 ) << integer << “ “ << setfill(‘*’) << setprecision (2) << fixed << ‘$’ << setw(10) << dlrAmnt << setfill(‘ ‘) << setw( 3 ) <
}

Please enter an integer, a dollar amount and a character. 12 123.45 G

Thank you. You entered: 12 $****123.45 G

THANK YOU!