C++ Introduction to C++ Programming

8/6/2019 C++ Introduction to C++ Programming

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BITG 1113:Introduction to theIntroduction to the

C++ languageC++ language

LECTURE 3


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Learning outcomes :Learning outcomes :

To know basic structure of C++programming

1. To introduce the concepts of

- data types

- constants

- variables- C++ operators

2. To introduce output manipulators


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main() function

//Written by: Rosmiza Wahida

/*This program is to calculate the area

of a cylinder*/

#define pi 3.142

float A_cyl;

int main()

{

float radius, height;

coutradius;

coutheight;

A_cyl = 2*pi*radius*height;

cout


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C++ program is made up of a global declaration section andone or more functions

Preprocessor directive & global declaration section comeat the beginning of the program

Function contains two types of codes

Declaration (local declaration)

Data that youll be using in the function

Also called local declaration because only visible

to the function that contain them Statement

Instructions to the computer to do something

Structure ofa C++ Program


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In Figure 1, the program is to calculate the area ofa cylinder.

This program consist of :

Comments Preprocessor directive

Standard namespace

Global declaration

main() function

Function header

Local declaration

Statements



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Preprocessor directives

- also known as pre-compiler directives - specialinstructions to the preprocessor that tell it how to prepareyour program for compilation

- #includeA command that tells the preprocessor, it needinformation from selected libraries known as headerfiles


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In Figure 1, the preprocessor directive start with apound sign (# is a syntax in C++) #include

include tells the preprocessor that you want the libraryin the < >

Tells the compiler to include input/output streamheader file in the program

The program need this header file because it will print

a message to the console (monitor) All preprocessor directive starts withpound sign (#)

Format or syntax of this directive must be exact

No space between # and include



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using namespace std;

Tells the compiler where to look for names in thelibraries.

These names have been organized into areasknown as namespaces.

The namespaces for standard system libraries isstandard, std.



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- intmain( )

The word intsays that the function will return an integer value to theoperating system (main function)

Statements in main function are to print message and to terminate

the program


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Example of comments


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Comments cannot be nested (comments insidecomments)

Once the compiler sees an opening block-

comment token, it ignores everything it sees until itfinds the closing token Therefore, the opening token of nested comment is not

recognized and the ending token that matches the firstopening token is left standing on its own

Comments


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Figure 2 Example of nested comments


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Reserved word/ Keyword

C and C++ Reserved Words

auto

breakcasecharconst

continuedefault

do

doubleelseenumexternfloatfor

goto

ifintlong

registerreturnshort

signedsizeofstaticstructswitchtypedef

unionunsigned

voidvolatilewhile

C++ Reserved Words

asmboolcatchclasscin

const_cast

cout

deletedynamic_

castexplicitfalsefriendinline

interrupt

mutablenamespac

enew

operatorprivate

protectedpublic

registerreinterpret_cast

static_caststring

templatethisthrow

truetry

typeidtypenameusingvirtualwchar_t

A word that has special meaning in C++. Used only

for their intended purpose.Keywords cannot beused to name identifiers.

All reserves word appear in lowercase.


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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 athrough z, digits 0 through 9 and also underscore ( _ )

Rules for identifier

The first character must be alphabetic character orunderscore

It must consists only of alphabetic characters, digits andunderscores, cannot contain spaces

It cannot duplicate any reserved word

C++ is case-sensitive; this means that NUM1, Num1, num1,and NuM1 are four completely different words.


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Examples of valid and invalid names

Validnames

A

student_name _aSystemName

pi

al

stdntNm

_anthrSysNm

PI

Invalidnames

$sum // $ is illegal

2names // cant startwith 2

stdnt Nmbr // cant havespace

int // reserved word

Identifiers


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Constants Data values that cannot be changed during the

execution of a program

Types of constant Integer constant

Float constant

Numbers with decimal part

Character constant

Enclosed between two single quotes ()

String constant

A sequence of zero or more characters enclosed indouble quotes ()

Symbolic constant

Define constant and memory constant


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Constants

Three different ways

Literal constants An unnamed constant used to specify data

If the data cannot be changed, we can simplycode the data value itself in a statement

E.g

A // a char literal

5 // a numeric literal 5

a + 5 // numeric literal

3.1435 // a float literal

Hello // a string literal


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0

Defined constant Another way to designate a constant is to use the

preprocessor command define

Like other preprocessor commands, it is also

prefaced with the pound sign (#)

Placed at the beginning of a program to make it easyto find and change

E.g #define pi 3.142

The way define work is that the expressions thatfollows the name (3.142) replaces the namewherever it is found in the program (like search and

replace command)

Constants


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Memory constant Use a type qualifier to indicate that data cannot be

changed and to fix the contents of the memory location

C++ provides the capability to define a named constantwhere we can add the type qualifier, constbefore thedefinition

E.g

const float pi = 3.142;

Constants


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//Written by: Rosmiza Wahida

/*This program is to calculate the area of a

cylinder*/

#define pi 3.142

float A_cyl;

int main()

{

float radius, height;

coutradius;

coutheight;

A_cyl = 2*pi*radius*height;

cout


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Data types

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

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

Functions also have types which is determined

by the data it returns


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Data Type

Standard


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C++ contains five standard types void

int (short for integer)

char (short for character)

float ( short for floating point)

bool (short for boolean)

They serves as the basic building blocks forderivedtypes (complex structures that are built using thestandard types

Derived types arepointer, enumerated type, union,array,structure and class

Data types


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Data types

void Has no values and operations

Both set of values are empty

char Any value that can be represented in the

computers alphabet

A char is stored in a computers memory as aninteger representing the ASCII code

A character in C++ can be interpreted as a smallinteger(between 0 and 255). For this reason, C++treats a character like integer.


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Float A number with fractional part such as 43.32

C++ supports three types of float

float

double long double

Data types

Type Byte

Size

Precision Range

float 4 6 10-37 ..1038

double 8 15 10-307 ..10308

long double 16 19 10-4931 ..104932

Typical float size


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Boolean (logical data)

C++ support bool type

C++ provides two constant to be used

True False

Is an integral which is when used with otherintegral type such as integer values, it converted

the values to 1 (true) and 0 (false)

Data types


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Figure 4: Variables in memory

Variables


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Variableinitialization

Initializer establishes the first value that the variable willcontain

To initialize a variable when it is defined, the identifier is

followed by the assignment operator (=) and then theinitializer which is the value the variable is to have when thefunctions starts

int count = 0;

int count , sum = 0;

Only sum is initialize.

int count=0 , sum = 0; OR int count =0; int sum = 0;


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Assignment Operator

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 %=x y = y%x y=1

Assume int x = 4, y=5, z=8;


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RelationalOperators

Sample Expression Value

> y > x T

< y < 2 F

> = x > = 3 T

< = y < = x F

EqualityOperators

Sample Expression Value

= = x = = 5 T

! = y ! = 6 F

Relational AndEqualityOperator

int y=6, x=5;


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Logical Operators Called Sample Operation

&& AND expression1 && expression 2

| | OR expression1 | | expression2

! NOT ! expression

Logical Operator

expression !expression Sample

Expression

F T !(x = = 60)

T F !(x ! = 60)

Example : Assume int x = 50


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expression1 expression2 expression1 | |

expression2

Sample Expression

F F F ( y > 10) | | ( z


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Operator Called Sample

Expression

Similar

Expression

Explanation

++ preincrement ++a a = a +1

a += 1

Increment a by 1, then use

the new value of a in

expression in which a reside

++ postincrement a++ a = a +1

a += 1

Use the current value of a in

the expression which a

reside, then increment a by 1

- - predecrement - - a a = a -1

a -= 1

Decrement a by 1, then use

the new value of a in

expression in which a reside

- - postdecrement a - - a = a -1

a -= 1

Use the current value of a in

the expression which a

reside, then decrement a by

1

Increment anddecrement Operator


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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

OperatorPrecedence


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Example 1:

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

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

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

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

3. a*b/(-10)*d

4. 200/(-10)*d

5. -20*d

6. -160

Example 2:

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

d *= ++b a/3 + c

1. d *= ++b a/3+ c

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

3. d*=7- 5+c

4. d*=2 + c

5. d*= 7

6. d = d*7

7. d = 28

OperatorPrecedence


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/*Evaluate two complex expression*/

#include using namespace std;

void main ( )

{

int a =3, b=4, c = 5, x, y;

cout


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Input / output function

Output Symbol use is (


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FormattingOutput

We can identify functions to perform special task.

For the input and output objects, these functionshave been giving a special name: manipulator.

The manipulator functions format output so that it ispresented in a more readable fashion for the user.

Must includeheader file.

#include header file contains

function prototypes for the stream manipulatorsthat enable formatting of streams of data.


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Output Manipulators

The lists of functions in thelibrary file:

Manipulators Use

endl

dec

oct

hex

fixed

showpoint

setw()

setprecision

setfill()

New line

Formats output asdecimal

Formats output as octal

Formats output as

hexadecimal

Set floating-point decimals

Showsdecimal in floating-

point values

Sets width of output fields

Specifiesnumberofdecimalsforfloating point

Specifies fill character


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//demonstrate the output manipulator

#include

#include

using namespace std;

int main( )

{

char aChar;

int integer;

float dlrAmnt;

cout integer>>dlrAmnt >> aChar;

cout

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