part 1 basics c++

8/9/2019 Part 1 Basics c++

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C++ PROGRAMMING SKILLS

Part 1

Basics of C++

C++ Overview

Elements I / O

Assignment and Comments

Formatted Output


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History ofC and C++

BCPL 1967By Martin RichardsLang. to write OS

NO Data Type

B :By Ken ThompsonUsed to create early UNIX

@ Bell lab's 1970NO Data Type

C :By Dennis Ritchie @ Bell labs-UNIX written in C-HW Independent

-many versions in late 1970s

OO Features

C++: ByBjarne Stroustrap

Early1980s @ Bell labsProvides OO programming

Standard ANSI C

In 1980 was approved

Java: In 1995 bySun Microsystems

OO Features

+

+

+

+


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Arithmetic

Arithmetic calculations Use * for multiplication and / for division

Integer division truncates remainder

7 / 5 evaluates to 1

Modulus operator returns the remainder

7 % 5 evaluates to 2

Operator precedence

Some arithmetic operators act before others (i.e.,multiplication before addition)

Be sure to use parenthesis when needed

Example: Find the average of three variables a, b and c

Do not use: a + b + c / 3

Use: (a + b + c ) / 3


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Equality and Relational Operators

Sta nda rd a lge bra icequality op erato r orrela tiona l operator

C++ eq ua lityor relationa loperator

Exampleo f C++condition

Mea ning o fC++ cond ition

Relational operators

> > x> y x is r at r t an y

< < x < y x is less t an y

u >= x>= y x is reater t an or equal to y

e


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Logical Operators

Truth TableMeaningOperator in C++

OUTPUTINPUT

Exp1 Exp2

F

FF

T

F F

F TT F

T T

Logical AND&&

F

T

T

T

F F

F T

T F

T T

Logical OR

||

T

F

F

T

Logical NOT!


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Operators Precedence update

Operator(s) Operation(s) Order of evaluation (precedence)

() Parentheses Evaluated first. If the parentheses are nested, the expression

in the innermost pair is evaluated first. If there are severalpairs of parentheses on the same level (i.e., not nested),they are evaluated left to right.

, +, - Logical NOT, signs Evaluated second. If there are several, they reevaluated right to left.

*, /, or% Multiplication DivisionModulus

Evaluated third. If there are several, they reevaluated left to right.

+or- AdditionSubtraction

Evaluated fourth. If there are several, they areevaluated left to right.

>, =,


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Memory Concepts

Variable names

Correspond to locations in the computer's memory

Every variable has a name, a type, a size and a value

Whenever a new value is placed into a variable, it replacesthe previous value - it is destroyed

Reading variables from memory does not change them

A visual representation

integer1 45


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Variable Names (Identifiers)

Letter + {Letters and/or Digits and/or ( _ )

_ +Letter+{Letters and/or Digits and/or ( _ )

CorrectionExplanation ?Invalidforty_Hours , hours40Begin with a digit40Hours

get_Date , getDateBlanks not allowedGet Date

box_22 , box22The hyphen(-) is minusBox-22

costInUSDollarSpecial symbols notallowed

cost_in_$

int_1Reserved word in C++int

Underscore character ( _ )

Naming Convention(Style)

Variables LengthInYard , hours

FunctionsCalcAverage , Cube(27)

ConstantMAX_HOUR , LIMIT


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Data Types short int :Range of values ( 32,767 ).

long int :Range of values ( 2,147,483,647 ).

int : Integer numbers float: floating point used for working with real numbers.

double: is a floating point type much like float , but it can store a value ofmuch greater magnitude with greater precision.

Bool*: is a boolean data type can take two value TRUE or FALSE.

*Note:- bool data type is provided by ANSI/ISO C++ standard. It is undefined in Borland Turbo C++.

char : character data type (alpha,digit,special-symbol or space).

A single character with its value quoted with single-quotation

egs. A , a , $ , , 8

string: for working with multiple characters including letters, numbers ,special symbols and spaces its value quoted with double- quotation.

egs. C++ , Computer Science , .

Letter S.Symbol Space Digit


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Declaration of Variables

Data Type Identifier1, Identifier2,;

Examples and preference:

charLetter, middleInt , ch;

charLetter;charmiddleInt;charch;

Constant Variables

constData Type Identifier=value;

Examples:

conststringSTARS=*****;constcharch=$;const floatMAX_Hour=40.0


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Assignment Statement

Store the value of the Expression into the variable, any previous value of the variableis destroyed.

Example:Giving the declarations

string firstname;

charletter;int num;

Remark :Double or more assignment allowed and precedence from Right-to-Left

eg. N1=n2=n3=5;

Variable = Expression ;

firstname=Sara;num = 5;num=5*5-3;letter=S

Valid Assignment

firstname=Sara;firstname=;

letter=S

Invalid Assignment


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Output statement

Example: Given ch=2 and firstname=Ali

and lastname=Ahmad

cout


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Comments

C++ Preprocessor

#include :- This line known as Preprocessor Directive its nothandled by C++ compiler but by a program known as Preprocessor.

iostream :- Headerfile contains declarations of I/O facilities.

Preprocessor program acts as a filter before compilation.

/* ..Text... Text */

// Text

For Multiple Lines

For Single Line

The compiler ignores comments (Not executable)

Source program PreprocessorExpanded Source

programC++ Compiler


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Input statement

cin >> variable1 >> variable2 ;

It needs #include preprocessor directive that contain istream cinostream cout.

cin>>Length>>width;cin>>Length;cin>>width;

Example:-

The Same

cin>>i>>ch>>x; 25 A 16.9

1:-

2:-

i=25 ch=A x=16.9

Statement Data Contents after input

3:- cin>>i>>j>>x; 12 8 i=12 j=8 (computer wait for the third number)

cin>>i>>x; 46 32.4 15 i=46j=32.4 (15 is held for later input)4:-

New line character \n is considered one charactereg. cout


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Input statement(cont.)

Note :- cant input SPACE character , the >> skips white space(blank) character.

cin.get() FUNCTION READS ONE CHARACTER FROM THEKEYBOARD (Does not skips space characters)

eg.

ch1=cin.get() R cin>>ch1

ch2= cin.get() ch2=cin.get()

ch3=cin.get() 1 cin>>ch3

Given input: R 1


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Operators Precedence update

Operator(s) Operation(s) Order of evaluation (precedence)

() Parentheses Evaluated first. If the parentheses are nested, the expression in the

innermost pair is evaluated first. If there are several pairs of

parentheses on the same level (i.e., not nested), they are evaluated

left to right.

!, +, - Logical NOT, signs Evaluated second. If there are several, they are evaluated right to left.

*, /, or% Multiplication Division

Modulus

Evaluated third. If there are several, they are evaluated left to right.

+or- Addition

Subtraction

Evaluated fourth. If there are several, they are evaluated left to right.

>>, , =,


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C++ program development goes through six steps: Step1: Edit (using text editor to type, correct and save the program

file).

Step2: preprocessor, automatically before compile, executes toinclude other text files in the file to be compiled.

Step3: Compile , the compiler translates the C++ code intomachine language (also called object-code).

Step4: Link , it is linking any used functions that are definedelsewhere such as standard libraryfunctions, or private libraryfor agroup ofprogrammers, linker, links the object code with the code for

the missing functions to provide full code Step5: Load, a program before executing , must be loaded into the

main memory, loader does this task , loading code from disk.

Step6: Execute, the computer under the control of its CPUexecutes the program. Instruction by instruction.

Phases of C++ Programs


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Phases o C++ Pro ra s:

1 dit

2 Preprocess

3 Co pile

4. Link

5. Load6. Execute

Loader

main

Memory

Program is created

inthe editor and storedon disk.

Preprocessorprogramprocesses the code.

Loader puts programin memory.

CPU takes each

instruction andexecutes it, possiblystoring new datavalues as the

programexecutes.

CompilerCompiler createsobject code andstores

it on disk.

Linker links the objectcode with the libraries,creates a.out and

stores it on disk

Editor

Preprocessor

Linker

CPU

main

Memory

.

.

.

.

.

.

.

.

.

.

.

.

Disk

Disk

Disk

Disk

Disk

illustration of C++ Program Phases


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Structure of C++ program

Ever y C++ program must have a function named main. The programmer can choose to

decompose the program into several parts (user-defined functions). Think ofmain as themaster and the otherfunctions are the servants.

The execution always starts with main.

#include

int main( ){ Declarations ;

Executable Statement_1 ;

Executable Statement_2 ;

:

Executable Statement_n ;

return 0;}

Preprocessor Directive

Type of returned value

Marks the start of themain function (program)

Marks the end of themain function (program)

Headerfile facilitateI/O

Returning 0 meansevery things is OKelse(1,2,..) somethingwent wrong (Exit Status)


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C++ Programming Examples

C++ language

Facilitates a structured and disciplinedapproach to computer program design

Following are several examples The examples illustrate many important

features of C++

Each example is analyzed one statement at atime.


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1. Comments

2. Load

3.main

3.1 Print "Welcometo C++\n"

3.2 exit (return 0)

1 // Fig.1.2:fig01_02.cpp

2 // Afirstprogramin C++

3 #include

4

5 intmain()

6 {

7 cout


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A Simple Program: Printing a Line of Text

cout Standard output stream object

Connected to the screen


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A Simple Program: Printing a Line of Text

There are multiple ways to print text Following are more examples

Escape equence escripti n

\n Newline. P siti n thescreencursor to the

beginningofthenext line.

\t Horizontal tab. ove thescreencursor to thenexttab stop.

\r Carriagereturn. Position thescreencursor to the

beginningofthecurrent line; onot advance to thenext line.

\a Alert. ound thesystem bell.

\\ Backslash. Used toprint a backslash character.

\" oublequote. Used toprint adoublequotecharacter.


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1. Load

2.main

2.1 Print "Welcome"

2.2 Print "to C++!"

2.3 newline

2.4 exit (return 0)

Program OutputWelcometo C++!

1 // Fig.1.4:fig01_04.cpp

2 // Printingaline with multiple statements

3 #include

4

5 intmain()

6 {

7 cout


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1. Load

2.main

2.1 Print "Welcome"

2.2 newline

2.3 Print "to"

2.4 newline

2.5 newline

2.6 Print "C++!"

2.7 newline

2.8 exit (return 0)

Program Output

1 // Fig.1.5:fig01_05.cpp

2 // Printing multiplelines witha single statement

3 #include

4

5 intmain()

6 {

7 cout


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Another Program: Adding Two Integers

>> (stream extraction operator) When used with cin, waits for the user to input a value andstores the value in the variable to the right of the operator

The user types a value, then presses the Enter (Return) key tosend the data to the computer

Example:int myVariable;

cin>> myVariable;

Waits for user input, then stores input inmyVariable

= (assignment operator) Assigns value to a variable

Binary operator (has two operands) Example:

sum= variable1 + variable2;


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1. Load

2. main

2.1 Initialize variables

integer1, integer2,and sum

2.2 Print "Enter firstinteger"

2.2.1 Get input

2.3 Print "Entersecond integer"

2.3.1 Get input

2.4 Add variables and putresult into sum

2.5 Print "Sum is"

2.5.1 Output sum

2.6 exit (return 0)

Program Output

1 // Fig.1.6:fig01_06.cpp

2 // Additionprogram

3 #include

4

5 intmain()

6 {7 int integer1,integer2, sum; // declaration

8

9 cout >integer1; //readaninteger

11 cout >integer2; //readaninteger

13 sum=integer1 + integer2; //assignment of sum

14 cout


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Built-in (Library) Function

Function Exponentiation

pow (x, y) x is raised to powery; (xy )sqrt (x) Square-root ofxsin (x) Sine of x cos (x) Cosine ofx tan (x) Tangent of x exp (x) Exponentiation ofx, ( ex)fabs (x) Absolute Value ofx, | x |log (x) Logarithm ofx (base e)log10 (x) Logarithm ofx (base 10)floor (x) Rounding-down xceil (x) Rounding-up x

______etc. {there are more}_______________________Eg.1. floor (9.2) = 9.0Eg.2. floor (-9.8) = -10.0 Remark:you need to include to be able to use these

functions. In newer versions it is #include


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Good Programming practices

Keep it simple do not stretch the language.

Read C++ manual.

Experiment a feature by writing a simple program and test it.

Start your program with a comment to indicate what the programdoes?

Use new line \n to make output more organized. Indent the body of each function one level, more indents for nesting.

Choose meaningful variables, constants and function names.

Use spaces after commas, operators and new lines betweendeclaration and executable statement.

One statement per line.Note: The function time(0) returns the current calendar time in seconds

calculated from 1970.

It needs: #include // turbo C++

#include // Visual C++


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Common programming Errors

Divide by zero. Not including iostream for input/output operations.

Forgetting the (;) at end of each statement.

Using % with non-integer.

Ifa space found between the pair-of-symbols for therelational operators. (i.e., > = instead of >= ).

Confusing the equality == with the assignment =.

Reversing the order of the relational operators

(i.e., => isntead of >=).


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Formatted Output

setwcan be used to specify the width o

fthe

field that the next value o

foutputwill be printed in. To use it, you must include headerfile.

eg1:-

int num=12;

cout


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Formatted Output(cont1)precision and setprecision for printing formatted floating point values

You may set the Number of

Digits that appear on the right of

the decimal-point the wayyou like it to be.

it can be done by either setprecision stream manipulator, or precision memberfunction.

eg. Using both to output the square root of 2

#include#include

#includeint main( ){double root2=sqrt(2.0);int places;cout


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11.41.411.4141.41421.414211.414214

1.41421361.414213561.414213562

Output

1

1.41.41

1.4141.41421.414211.4142141.41421361.414213561.414213562

Square root of 2 with precision 0-9 usingprecision memberfunction

Using setprecision manipulator

Formatted Output(cont2)

part 1 basics c++

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