starting out with c++, 3 rd edition 1 chapter 2. introduction to c++

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Starting Out with C++, 3rd Edition

Chapter 2. Introduction to C++

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2.1 The Parts of a C++ Program

• C++ programs have parts and components that serve specific purposes.

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Program 2-1

//A simple C++ program

#include <iostream.h>

void main (void)

{

cout<< “Programming is great fun!”;

}

Program Output:

Programming is great fun!

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Table 2-1Character Name Description // double slash Marks the beginning of a comment. # Pound sign Marks the beginning of a preprocessor

directive < > Opening and

closing brackets

Encloses a filename when used with the #include directive

( ) Opening and closing parenthesis

Used in naming a function, as in int main ()

{ } Opening and closing braces

Encloses a group of statements, such as the contents of a function.

" " Opening and closing quotation marks

Encloses a string of characters, such as a message that is to be printed on the screen

; Semicolon Marks the end of a complete programming statement

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2.2 The cout Object

• Use the cout object to display information on the computer’s screen. The cout object is referred to as the standard

output object. Its job is to output information using the

standard output device

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Program 2-2

// A simple C++ program


void main (void)

{

cout<< “Programming is “ << “great fun!”;

}

Output:

Programming is great fun!

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Program 2-3

// A simple C++ program#include <iostream.h>

void main (void){cout<< “Programming is “;cout << “ great fun!”;

}

Output:Programming is great fun!

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Program 2-4// An unruly printing program


void main(void)

{

cout << "The following items were top sellers";

cout << "during the month of June:";

cout << "Computer games";

cout << "Coffee";

cout << "Aspirin";

}

Program Output

The following items were top sellersduring the month ofJune:Computer gamesCoffeeAspirin

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New lines

• cout does not produce a newline at the end of a statement

• To produce a newline, use either the stream manipulator endl

• or the escape sequence \n

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Program 2-5

// A well-adjusted printing program


void main(void)

{

cout << "The following items were top sellers" << endl;

cout << "during the month of June:" << endl;

cout << "Computer games" << endl;

cout << "Coffee" << endl;

cout << "Aspirin" << endl;

}

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Program Output

The following items were top sellers

during the month of June:

Computer games

CoffeeAspirin

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Program 2-6

// Another well-adjusted printing program


void main(void)

{

cout << "The following items were top sellers" << endl;

cout << "during the month of June:" << endl;

cout << "Computer games" << endl << "Coffee";

cout << endl << "Aspirin" << endl;

}

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Program Output



Computer games

Coffee

Aspirin

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Program 2-7

// Yet another well-adjusted printing program


using namespace std;

void main(void)

{

cout << "The following items were top sellers\n";

cout << "during the month of June:\n";

cout << "Computer games\nCoffee";

cout << "\nAspirin\n";

}

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Program Output



Computer games

Coffee

Aspirin

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Table 2-2

Table 2-2 Common Escape Sequences Escape Sequence

Name Description

\n Newline Causes the cursor to go to the next line for subsequent printing

\t Horizontal tab

Causes the cursor to skip over to the next tab stop

\a Alarm Causes the computer to beep \b Backspace Causes the cursor to back up, or

move left one position \r Return Causes the cursor to go to the

beginning of the current line, not the next line.

\\ Backslash Causes a backslash to be printed \' Single quote Causes a single quotation mark

to be printed \" Double quote Causes a double quotation mark

to be printed

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2.3 The #include Directive

• The #include directive causes the contents of another file to be inserted into the program

• Preprocessor directives are not C++ statements and do not require semicolons at the end

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2.5 Variables and Constants

• Variables represent storage locations in the computer’s memory. Constants are data items whose values do not change while the program is running.

• Every variable must have a declaration.

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Program 2-8


void main(void)

{

int value;

value = 5;

cout << “The value is “ << value << endl;

}

Program Output:

The value is 5

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Assignment statements:

Value = 5; //This line is an assignment statement.

• The assignment statement evaluates the expression on the right of the equal sign then stores it into the variable named on the left of the equal sign

• The data type of the variable was in integer, so the data type of the expression on the right should evaluate to an integer as well.

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Constants

• A variable is called a “variable” because its value may be changed. A constant, on the other hand, is a data item whose value does not change during the program’s execution.

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Program 2-10


void main (void)

{

int apples;

apples = 20;

cout<< “Today we sold “ << apples << “ bushels\n”;

cout << “of apples.\n”;

}

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Program Output

Today we sold 20 bushels

of apples.

Where are the constants in program 2-10?

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Constants from Program 2-10

Constant Type of Constant20 Integer constant"Today we sold " String constant" bushels\n" String constant"of apples.\n" String constant

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2.6 Focus on Software Engineering: Identifiers

• Must not be a key word• Should be mnemonic (give an indication of what

the variable is used for)• The first character must be a letter or an

underscore• The remaining may be letters, digits, or

underscores• Upper and lower case letters are distinct

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Table 2-3 The C++ Key Words

asm auto break bool case catch char class const const_cast continue default de lete do double dynamic_cast e lse enum explicit extern fa lse float for fr iend goto if in line in t long mutab le namespace new operator private protected public reg ister re in terpret_cast re turn short signed sizeof sta tic sta tic_cast struct switch template th is throw true try typedef typeid typename union unsigned using virtua l vo id vo la tile wchar_t while

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Table 2-4 Some Variable Names

Variable Name Legal or Illegal?

dayOfWeek Legal

3dGraph Illegal. Cannot begin with a digit.

_employee_num Legal

june1997 Legal

Mixture#3 Illegal. Cannot use # symbol.

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2.7 Integer Data Types

• There are many different types of data. Variables are classified according to their data type, which determines the kind of information that may be stored in them. Integer variables only hold whole numbers.

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Table 2-5

Table 2-5 Integer Data Types, Sizes and RangesData Type Size Rangeshort 2 Bytes -32,768 to +32.767unsigned short 2 Bytes 0 to +65,535int 4 Bytes -2,147,4833,648 to +2,147,4833,647unsigned int 4 Bytes 0 to 4,294,967,295long 4 Bytes -2,147,4833,648 to +2,147,4833,647unsigned long 4 Bytes 0 to 4,294,967,295

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Program 2-11// This program has variables of several of the integer types.#include <iostream.h>

void main(void){

int checking;unsigned int miles;long days;

checking = -20;miles = 4276;days = 184086;cout << "We have made a long journey of " << miles;cout << " miles.\n";cout << "Our checking account balance is " << checking;cout << "\nExactly " << days << " days ago Columbus ";cout << "stood on this spot.\n";

}

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Program Output

We have made a long journey of 4276 miles.

Our checking account balance is -20

Exactly 184086 days ago Columbus stood on this spot.

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Program 2-12

// This program shows three variables declared on the same

// line.


void main(void)

{

int floors,rooms,suites;

floors = 15;

rooms = 300;

suites = 30;

cout << "The Grande Hotel has " << floors << " floors\n";

cout << "with " << rooms << " rooms and " << suites;

cout << " suites.\n";

}

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Program Output

The Grande Hotel has 15 floors

with 300 rooms and 30 suites.

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Hexadecimal and Octal Constants

• Hexadecimal numbers are preceded by 0x Hexadecimal F4 would be expressed in C++ as

0xF4

• Octal numbers are preceded by a 0 Octal 31 would be written as 031

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2.8 The char Data Type

• Usually 1 byte long

• Internally stored as an integer

• ASCII character set shows integer representation for each character

• ‘A’ == 65, ‘B’ == 66, ‘C’ == 67, etc.

• Single quotes denote a character, double quotes denote a string

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Program 2-13

// This program demonstrates the close relationship between

// characters and integers.


void main(void)

{

char letter;

letter = 65;

cout << letter << endl;

letter = 66;


}

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Program Output

A

B

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Program 2-14

// This program uses character constants


void main(void)

{

char letter;

letter = 'A';


letter = 'B';


}

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Program Output

A

B

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C-Strings

• C-Strings are consecutive sequences of characters and can occupy several bytes of memory.

• C-Strings always have a null terminator at the end. This marks the end of the string.

• Escape sequences are always stored internally as a single character.

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Program 2-15// This program uses character constants#include <iostream.h>

void main(void){

char letter;

letter = 'A';cout << letter << '\n';letter = 'B';cout << letter << '\n';

}

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Program Output

A

B

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Review key points regarding characters, strings, and C-strings:• Printable characters are internally represented by numeric codes. Most

computers use ASCII codes for this purpose.

• Characters occupy a single byte of memory.

• C-Strings are consecutive sequences of characters and can occupy several bytes of memory.

• C-Strings always have a null terminator at the end. This marks the end of the C-string.

• Character constants are always enclosed in single quotation marks.

• String constants are always enclosed in double quotation marks.

• Escape sequences are always stored internally as a single character.

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2.9 The C++ string Class

• The string class is an abstract data type.

• It provides capabilities that make working with strings easy and intuitive.

• You must us the #include <string> statement.

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2.10 Floating Point Data Types

• Floating point data types are used to declare variables that can hold real numbers

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Table 2-7Table 2-7 Floating Point Data Types on PCs Data Type Key Word Description

Single Precision float 4 bytes. Numbers between + 3.4E-38 and + 3.4E38

Double Precision double 8 bytes. Numbers between +1.7E-308 and +1.7E308

Long Double Precision

long double 8 bytes. Numbers between +1.7E-308 and +1.7E308

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Program 2-17

// This program uses floating point data types


void main(void)

{

float distance;

double mass;

distance = 1.495979E11;

mass = 1.989E30;

cout << "The Sun is " << distance << " kilometers away.\n";

cout << "The Sun\'s mass is " << mass << " kilograms.\n";

}

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Program Output

The Sun is 1.4959e+11 kilometers away.

The Sun's mass is 1.989e+30 kilograms.

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Floating Point Constants

• May be expressed in a variety of ways

• E notation

• decimal notation

• (no commas)

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2.11 The bool Data Type

• Boolean variables are set to either true or false

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Program 2-18#include <iostream.h>

void main (void)

{

bool boolValue;

boolValue = true;

cout << boolValue << endl;

boolValue = false;

cout << boolValue << endl;

}

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Program Output

1

0

Internally, true is represented as the number 1 and false is represented by the number 0.

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2.12 Focus on Software Engineering: Determining the Size of a Data Type

• The sizeof operator may be used to determine the size of a data type on any system.

cout << “The size of an integer is “ << sizeof(int);

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Program 2-19


void main (void)

{

long double apple;

cout << “The size of an integer is “ << sizeof(int);

cout << “ bytes.\n”;

cout << “The size of a long integer is “ << sizeof(long);

cout << “ bytes.\n”;

cout << “An apple can be eaten in “ << sizeof(apple);

cout << “ bytes!\n”;

}

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Program Output

The size of an integer is 4 bytes.

The size of a long integer is 4 bytes.

An apple can be eaten in 8 bytes!

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2.13 Focus on Software Engineering: Variable Assignment and Initialization

• An assignment operation assigns, or copies, a value into a variable. When a value is assigned to a variable as part of the variable’s declaration, it is called an initialization.

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Program 2-20


void main (void)

{

int month = 2, days = 28;

cout << “Month “ << month << “ has “ << days << “ days.\n”;

}

Program output:

Month 2 has 28 days.

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2.14 Focus on Software Engineering: Scope

• A variable’s scope is the part of the program that has access to the variable.

• A variable must be declared before it is used.

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Program 2-21

// This program can't find its variable


void main(void)

{

cout << Value;

int Value = 100;

}

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2.15 Arithmetic Operators

• There are many operators for manipulating numeric values and performing arithmetic operations.

• Generally, there are 3 types of operators: unary, binary, and ternary. Unary operators operate on one operand Binary operators require two operands Ternary operators need three operands

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Table 2-8Table 2-8 Fundamental Arithmetic OperaotrsOperator Meaning Type Example

+ Addition Binary Total = Cost + Tax;- Subtraction Binary Cost = Total - Tax;* Multiplication Binary Tax = Cost * Rate;/ Division Binary SalePrice = Original/2;

% Modulus Binary Remainder = Value%3;

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Program 2-22// This program calculates hourly wages// The variables in function main are used as follows:// regWages: holds the calculated regular wages.// basePay: holds the base pay rate.// regHours: holds the number of hours worked less overtime.// otWages: holds the calculated overtime wages.// otPay: holds the payrate for overtime hours.// otHours: holds the number of overtime hours worked.// totalWages: holds the total wages. #include <iostream.h>

void main(void){

float regWages, basePay = 18.25, regHours = 40.0;float otWages, otPay = 27.78, otHours = 10;float totalWages;

regWages = basePay * regHours; otWages = otPay * otHours;totalWages = regWages + otWages;cout << "Wages for this week are $" << totalWages << endl;

}

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2.16 Comments

• Comments are notes of explanation that document lines or sections of a program.

• Comments are part of a program, but the compiler ignores them. They are intended for people who may be reading the source code.

• Commenting the C++ Way

//

• Commenting the C Way

/* */

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Program 2-23// PROGRAM: PAYROLL.CPP

// Written by Herbert Dorfmann

// This program calculates company payroll

// Last modification: 3/30/96


void main(void)

{

float payRate; // holds the hourly pay rate

float hours; // holds the hours worked

int empNum; // holds the employee number

(The remainder of this program is left out.)

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Program 2-24 // PROGRAM: PAYROLL.CPP

// Written by Herbert Dorfmann

// Also known as "The Dorfmiester"

// Last modification: 3/30/96

// This program calculates company payroll.

// Payroll should be done every Friday no later than

// 12:00 pm. To start the program type PAYROLL and

// press the enter key.

#include <iostream.h> // Need the iostream file because

// the program uses cout.

void main(void) // This is the start of function main.

{ // This is the opening brace for main.

float payRate; // payRate is a float variable.

// It holds the hourly pay rate.

float hours; // hours is a float variable too.

// It holds the hours worked.

int empNum; // empNum is an integer.

// It holds the employee number.


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Program 2-25

/*

PROGRAM: PAYROLL.CPP

Written by Herbert Dorfmann

This program calculates company payroll

Last modification: 3/30/96

*/


void main(void)

{

float payRate; /* payRate holds hourly pay rate */

float hours; /* hours holds hours worked */

int empNum; /* empNum holds employee number */


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Program 2-26

/*

PROGRAM: PAYROLL.CPP

Written by Herbert Dorfmann

This program calculates company payroll

Last modification: 3/30/96

*/


void main(void)

{

float payRate; // payRate holds the hourly pay rate

float hours; // hours holds the hours worked

int empNum; // empNum holds the employee number


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2.17 Focus on Software Engineering: Programming Style

• Program style refers to the way a programmer uses identifiers, spaces, tabs, blank lines, and punctuation characters to visually arrange a program’s source code.

Generally, C++ ignores white space. Indent inside a set of braces. Include a blank line after variable declarations.

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Program 2-27


void main(void){float shares=220.0;float avgPrice=14.67;cout <<"There were "<<shares<<" shares sold at $"<<avgPrice<<" per share.\n";}

Program Output

There were 220 shares sold at $14.67 per share.

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Program 2-28

// This example is much more readable than Program 2-26.


void main(void)

{

float shares = 220.0;

float avgPrice = 14.67;

cout << "There were " << shares << " shares sold at $";

cout << avgPrice << " per share.\n";

}

Program Output

There were 220.0 shares sold at $14.67 per share.

starting out with c++, 3 rd edition 1 chapter 2. introduction to c++

Documents

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c program c programs

simple c program

rd edition

void main void

specific purposes