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Chapter 1

INTRODUCTION

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Welcome to C++!

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A Simple C++ Program

// A first program in C++#include

int main()

{std::cout

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What is C++?

Has 2 parts: Preprocessor Directives

Main function

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Preprocessor Directives All directive begin with #

character E.g., #include , #define

Why preprocessor directives?

C++ defines only a small number ofoperation.

Most of the functions and symbols are

in Libraries.

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Main Function

All C++ program must have main()

function. All function start with a { and end

with a } symbol.

It is the body of the function.

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// Printing on one line with multiple statements

#include int main()

{

std::cout

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//Printing multiple lines with a single statement

#include

int main()

{

std::cout

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#include using namespace std;

int main(){

cout

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#include

using namespace std;

int main()

{ int num;

cout > num;

cout

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// Program that displays the sum of two numbers.#include using namespace std;

int main(){ int number1, number2,sum; // variable declarations

cout > number1; // read first integer into number1

cout > number2; // read second integer

sum = number1 + number2; // assignment of sum

cout

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Memory Concepts Variable names such as number1,

number2, and sumis correspond tolocationsin the computers memory.

Every variable has a name, a type,

and avalue

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Arithmetic in C++

C++ operation Arithmetic

operator

Algebraic

expression

C++

expressionAddition

Subtraction

MultiplicationDivision & integerdivision

Modulus

+-*

/

%

f + 7

p c

bm

x/y or x y

r mod s

f + 7

p c

b * m

x /y

r % s

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Integer division /yields an integer result E.g. 7 / 4 = 1 17 / 5 = 3

0/4 = 0 4/0 is undefined Modulus operator %yields the remainder

after integer division.

The modulus operator is an integeroperator

Can be used only with integer operands.

E.g. 7 % 4 = 3 17 % 5 = 215%0 is undefined

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Comments Are not part of the executable program

Comments are used for explaining difficult sections of code describe the program, author, date,

modification changes etc. documentation of variables and their

usage copyrighting

All comments must start with // Symbol /* and end with */ for multiplelines

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E.g./*

* Programmer: William Bell* Date completed: May 9,2003* Instructor: Janet Smith

* Class: CIS61** Calculates and displays the area and* circumference of a circle*/

Use // for single line

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Input Statement

Accepting data from the userthrough keyboard

Example

cin >> salary; //receive salary cin >> d >>f >>c; //receive 3 variable

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Output Statement

Print result to the screen

Example cout

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insert a line

cout

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Escape sequence Description

\n Newline. Position the screen cursor tothe beginning of the next line

\t Horizontal tab. Move the screen cursorto the next tab stop

\r Carriage return. Position the screencursor to the beginning of the currentline

\\ Blackslash. Used to print a blackslashcharacter

\ Single quote. Used to print a single quotecharacter

\ Double quote. Used to print a doublequote character

\a Alert. Sound the s stem bell

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Common Programming Errors

Debugging to find any error in the

program Types of Errors:

Syntax errors

Run-time errors

Logic errors

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Syntax Errors

Code violation during compilation

Example:

Missing semicolon

Undefined variable Did not close /* with */

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Run-time Errors

Illegal operation occur duringexecution

Example

Divide a number by zero Open an non existing file

Write to non existing printer

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Logic Errors

Passed Syntax and Run-time Errorsbut produce false result

It is usually causes by the algorithm

of the program

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I/O Manipulators Using library

setw(int n) sets width of next output valueonly to the argument.

setprecision(int n) set decimal places. Default is 6.

fixed output as decimal notation

scientific output as scientific notation

left left align . Use with setw()

right right align. Use with setw()

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setw( )

E.g.,int n=1234

cout

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output:

1 2 3 4

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setprecision()

The precisiondetermines themaximum number of digits that shallbe output to express floating-pointvalues, counting both the digits

before and after the decimal point.

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// setprecision example#include

#include using namespace std;

int main (){

double f =3.141596;cout

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Output:

3.1416 // rounded up3.14

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Fixed or Scientific

float n=12.345678;

cout

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float n=123.2345;

cout

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Left/Right

float n=123.456;

cout