Chapter 13 Computer Programs and Programming Languages A computer program is a series of instructions that directs a computer to perform tasks. Created by a programmer using a programming language. Low-Level Languages

• Assembly language is the second generation of programming languages.
• Machine language is the first generation of programming languages.
• Only language the computer directly recognizes.
• A source program contains the code to be converted to machine language.

Procedural language

• In a procedural language, the programmer writes instructions that tell the computer what to accomplish and how to do it. A compiler translate an entire program before executing it. An interpreter converts and executes one code statement at a time.
• The C programming language is used to write many of today's programs.
• COBOL (COmmon Business-Oriented Language) is designed for business applications, but easy to read because of the English-like statements.
• Object-Oriented Programming Languages and Program Development Tools

• An object-oriented programming (OOP) language allows programmers the ability to reuse and modify existing objects.
• Other advantages include: Objects can be reused, Work well in a RAD environment, Programmers create applications faster.
• Java is an object-oriented programming language developed by Sun Microsystems.
• XML allows Webs developers to create customized tags and use predefined tags to display content appropriately on various devices. -WML is a subset of XML and is used to design pages for microbrowsers.
• The Microsoft .NET Framework allows almost any type of program to run on the Internet or an internal business network, as well as computers and mobile devices.
• C++ is an extension of the C programming language.
• C# is based on C++ and was developed by Microsoft.
• F# combines the benefit of an object-oriented language with those of a functional language.
• A visual programming language is a language that uses a visual or graphical interface for creating all source code.

• PowerBuilder is a powerful program development RAD tool.
• A 4GL (fourth-generation language) is a nonprocedural language that enables users and programmers to access data in a database.
• An application generator is a program that creates source code or machine code from a specification of the required functionality.
• A macro is a seriess of statements that instructs an application how to complete a task.
• The macro are usually created in one of two ways: Record the macro with a macro recorder, Write the macro.

Web Page Development

• HTML is a special formatting language that programmers use to format documents for display on the Web.
• XHTML is a markup language that allows Web sites to be displayed more easily on mobile devices.
• Two application of XML are RSS 2.0 and ATOM.
• Web browsers can execute short programs to add interactive elements to Web pages.
• Programmers write scripts, applets, servlets, or ActiveX controls using a variety of languages.
• Web 2.0 allows Web sites to provide a means for users to: Share personal information, Allow users to modify Web site content, Have application software built into the site.
• Web page authoring software can create sophisticated Web pages that include images, video, audio, animation, and other effects

Multimedia Program Development

• Multimedia authoring software allows programmers, to combine text, graphics, animation, audio, and video in an interactive presentation.

Program Development

• Program development consists of a series of steps programmers use to build computer programs.

Step 1 - Analyze Requirements

• To initiate program development, programmer:
• i) review the requirements
• ii) meets with the system analyst and users
• iii) identifies input, processing, and output.

Step 2- Design Solution

• Design solution algorithm
• In structured design, the programmer typically begins with a general design and moves toward a more detailed design.
• Programmers use a hierarchy chart to show program modules graphically.
• With object-oriented (OO) design, the programmer packages the data and the program into a single object.
• The sequence control structure shows one or more actions following each other in order.
• The selection control structures tells the program which action to take, based on a certain condition.
• The repetition control structure enables a program to perform one or more actions repeatedly as long as a certain condition is met.
• A program flowchart graphically shows the logic in a solution algorithm.
• Flowcharting software makes it easy to modify and update flowcharts.
• UML (Unified Modeling Language) has been adopted as a standard notation for object modeling and development.

Step 3 - Validate Design

• Check for logic errors using test data.

Step 4 - Implement Design

• Implementation of the design includes using a program development tool that assists the programmer by:
• i) generating or providing some or all code
• ii) Writing the code that translates the design into a computer program
• iii) Creating the user interface.
• Extreme programming is a strategy where programmers immediately begin coding and testing solutions as soon as requirements are defined.

Step 5 - Test Solution

• The goal of program testing is to ensure the program runs correctly and is error free.
• Errors include syntax errors and logic errors
• Debugging the program involves removing the bugs
• A beta is a program that has most or all of its features and functionality implemented.

Step 6 - Document Solution

• In documenting the solution, the programmer performs two activities: Review the program code and all the documentation.

Chapter 12 System Development System development is a set of activities used to build an information system. A system is a set of components that interact to achieve a common goal. An information system (IS) is a collection of hardware, software, data, people, and procedures that work together to produce quality information.
-System development should follow three general guidelines:

1.  Group activities or tasks into phases 
2.  involve users
3. define standards.

• Project management is the process of planning, scheduling, and then controlling the activities during system development.
• To plan and schedule a project efficiently, the project leader identifies: Project scope, Required activities, Order of activities.
• Feasibility is a measure of how suitable the development of a system will be to the organization. Operational feasibility, Schedule feasibility, Technical feasibility, Economic feasibility.
• Documentation is the collection and summarization of data and information.
• Users and IT professionals refer to existing documentation when working with and modifying current systems.

Planning Phase

• The planning phase for a project begins when the steering committee receives a project request.
• Four major activities are performed for example review and approve the project requests, Prioritize the project requests, Allocate resources, Form a project development team.

Analysis Phase

• Process modeling (structured analysis and design) is an analysis and design technique that describes processes that transform inputs into outputs.
• An entity-relationship diagram (ERD) is a tool that graphically shows the connections among entities in a system.
• Entities are objects in the system that have data.
• A data flow diagram (DFD) is a tool that graphically shows the flow of data in a system.
• The project dictionary contains all the documentation and deliverables of a project.
• Structured English is a style of writing that describes the steps in a process.
• The data dictionary stores the data item's name, description, and other details about each data item.
• Object modeling combines the data with the processes that act on that data into a single unit, called an object.
• UML (Unified Modeling Language) has been adopted as a standard notation for object modeling and development.
• A use case diagram graphically shows how actors (users) interact with the information system.
• The system proposal assesses the feasibility of each alternative solution.
• The steering committee discusses the system proposal and decides which alternative to pursue.

Design Phase

• The design phase consists of two major activities for example Acquire hardware and software, Develop all of the details of the new or modified information system.
• Systems analysts typically develop two types of designs for each input and output.
• A prototype (proof of concept) is a working model of the proposed system. Prototypes have inadequate or missing documentation.

Implementation Phase

• The purpose of the implementation phase is to construct the new or modified system and then deliver it. Develop programs > Install and test the new system > Train users > Convert to the new system.
• Various tests should be performed on the new system. Unit test - verifies that each individual program or object works by itself. Systems test - verifies that all programs in an application work together properly. Integration test - verifies that an application works with other applications. Acceptance test - checks the new system to ensure that it works with actual data.
• Training involves showing users exactly how they will use the new hardware and software in the system.
• One or more of four conversion strategies can be used to change from the old system to the new system.

Operation, Support, and Security Phase

• The purpose of the operation, support, and security phase is to provide ongoing assistance for an information system and its users after the system is implemented. Perform maintenance activities > Monitor system performance > Assess system security.
• A computer security plan should do the following: Identify all information assets of an organization. Identify all security risks that may cause an information asset loss. For each risks, identify the safeguards that exist to detect, prevent, and recover from a loss.

Chapter 14 Enterprise Computer

Enterprise computing involves the use of computers in networks,such as LANs and WANs, or a series of interconnected networks that encompass a variety of different operating systems,protocols, and network architectures

Types of enterprises
-Retail 
-Manufacturing
-Service
-Wholesale
-Government 
-Educational
-Transportation

• Most traditional enterprises are organized in a hierarchical manner
• In an enterprise , users typically fall into one of four categories

1. Executive Management 
2. Middle Management
3. Operational Management
4. Non management Employees

• Enterprise information is the information is the information gathered in the ongoing operations of an enterprise-sized organization

- Business intelligence 

-Business process management

-Business process automation

• Managers coordinate resources by performing four activties

-Planning

-Organizing

-Leading

-Controlling

Information System in the Enterprise

An information system  is a set of hardware,software,data,people, and procedures that work together to produce information

• Functional units within an enterprise might include

-accounting and finance

-human resource

-engineering or product development

-manufacturing

-marketing 

-sales

-distribution

-customer

-information technology

• Acounting software manages everyday transactions
• Billing software helps the company reconcile purchases with customer payments
• Financial software helps managers budget , forecast, and analyze
• A human resources information system(HRIS) manages one or more human resources functions 
• Employee relationship management systems manage communication between employees and the business 
• Computer-aided design(CAD) uses computers and special software to aid in engineering , drafting , and design
• Computer-aided engineering (CAE) uses computers to test product designs
• Computer-aided manufacturing (CAM) is the use of computers to control production equipment
• Computer-integrated manufacturing (CIM) uses computers to integrate the many different operations of the manufacturing process
• Material Requirements Planning (MRP) uses software to help monitor and control processes related to production
• Manufacturing Resource Planning 11 (MRP11)is an extension of MRP and also includes software that helps in scheduling

A quality control system helps an organization maintain or improve the quality of its products or services

A marketing information system serves as a central repository for the tasks of a marketing department

• sales force automation(SFA) software equips traveling salespeople with the electronic tools they need to be more productive

Distribution system perform the following fucions

-Provide forecasting for inventory control

-Manage and track shipping of products

-Provide information and analysis on inventory in a warehouse

• Customer interaction management (CIM) software manages the day-to-day interactions with customers
• The information technology (IT) department makes technology decisions for the enterprise
• Web site management programs collect data designed to help organization make informed decisions regarding their Wed presence

General purpose information systems generally fall into one of five categories
-office information system 

-transaction processing system 

-management information system

-decision support system

-expert system

• Batch processing vs online transaction processing

Integrated Information Systems

-Customer relationship management manages information about customer,interactions with customers, past purchases and interests

-Enterprise resource planning provides centralized,integrated software to help mange and coordinate ongoing activities

-Content management system are information system that combine databases ,software, and procedures

Enter-Wide Technologies and Methodologies

Some technologies used in enterprises include

-portals

-data warehouses

-electronic data interchange

-extranets

-web services

-document management systems

-workflow

-virtual private networks

-A portal is a collection of links, content, and services presented on a Web page that are interesting for a particular job function.

-A data warehouse is a huge database that stores manages the data required to analyze historical and current transactions.

-Web services allow businesses to create products and B2B interactions over the Internet.

-A document management system (DMS) allows for storage and management of a company's documents.

-A workflow is a defined process that identifies the specific set of steps involved in completing a particular project or business process.

-A virtual private network (VPN) provides mobile users, vendors, and customers with a secure connection to the company network server.

Virtualization and cloud Computing

-Virtualization is the practice of sharing or pooling computing resources.

-Server virtualization: Provides the capability to divide a physical server logically into many virtual servers.

-Storage virtualization: Provides the capability to create a single logical storage device from many physical storage devices.

Enterprise Hardware

-Enterprise hardware allows large organizations to manage and store information and data using devices geared for: Heavy use, Maximum availability, Maximum efficiency.

-RAID duplicates data and implements duplication in different ways.

-Network attached storage (NAS) is a server that provides storage to users and information systems attached to the network.

-A storage area network (SAN) is a high-speed network that provides storage to other servers to which it attached.

-An enterprise storage system is a strategy that focuses on the availability, protection, organization, and backup of storage in a company.

-A blade server packs a complete computer server on a single card rather than a system unit.

-A thin client is a small terminal-like computer that mostly relies on a server for data storage and processing.

-The processing for a  thin client usually is done on a server.

High Availability, Scalability, and Interoperability

-A high-availability system continues running and performing tasks for at least 99% of the time.

-Scalability is a measure of how well computer hardware, software, or an information system can grow to meet increasing performance demands.

-Interoperability is the ability for an information system to share information with other information systems within an enterprise.

Backup Procedures

-Continuous data protection provides automatic data backup whenever data is changed in an enterprise.

-A disaster recovery plan is a written plan describing the steps a company would take a restore computer operations in the event of a disaster.

-Contains four major components: Emergency plan, Backup plan, Recovery plan, Test plan.

Chapter 11 Manage Computing Securely,Safely                     and Ethically

Computer Security Risks

• a computer security risk is any event or action that could cause a loss of or damage to computer hardware , software , data , information , or processing cability
• A cybercrime is an online or Internet-based illegal act for example hackers , crackers , script kiddies , corporate spie and etc

Internet and Network Attacks

• Information transmitted over networks has a higher degree of security risk than information kept on an organization premises
• an online security service is web site that evaluates our computer to check for Internet and e-mail vulerabilities

Computer virus-affects a computer negatively by altering the way                               the computer works
Worm -copies itself repeatedly , using up resources and possibly                   shutting down the computer or network 
Trojan horse-a malicious program that hides within or looks like a                         legitimate program
Rootkit-program that hides in a computer and allows someone from               a remote location to take full control

An infected computer has one or more of the following symptoms

• Operating system runs much slower than usual 
• Available memory is lee than expected 
• files becomes corrupted 
• Screen displays unusual message or image
• Music or unusual sound plays randomly
• Existing programs and files disappear 
• Programs or files do not work properly 
• Unknown programs or files mysteriously appear
• System properties change 
• Operating system does not start up 
• Operating system shuts down unexpectedly

User can take several precautions to protect their home and work computers and mobile devices from these malicious infections

• a botnet is a group of compromised computers connected to a network 
• a denial of service attack (DoS attack)disrupts computer access to Internet services
• a back door is a program or set of instructions in a program that allow user to bypass security controls
• spoofing is a technique intruders use to make their network or Internet transmission appear legitimate
• a firewall is hardware or software that protect a network resources from intrusion 

Intrusion detection software

• analyzes all network traffic 
• assesses system vulnerabilities
• identifies any unauthorized intrusions 
• notifies network administrators of suspicious behavior patterns or system breaches

Honeypot

• vulnerable computer that is set up to entice an intruder too break into it

Unauthorized Access and Use
Unauthorized access is the use of a computer or network without permission 
Unauthorized use is the use of a computer or its data for unapproved or possibly illegal activities

• organizations take several measures to help prevent unauthorized access and use

-acceptable use policy 
-disable file and printer sharing
-firewall
-intrusion detection software

• access control define who can access it, and what action they can take for example two-phase processes called identification and authentication , user name , password ,passphrase and CAPTCHA
• A possessed object is any item that we must carry to gain access to a computer or computer facility
• A biometric device authenticates a person identity by translating a personal characteristic into a digital code that is compared with a digital code in a computer
• digital forensics is the discovery, collection, and analysis of evidence found on computers and network 
• Many areas use digital forensics for example law enforcement ,criminal prosecutors , military intelligence , insurance agencies and information security departments 

Hardware Theft and Vandalism
Hardware theft is the act of stealing computer equipment
Hardware vandalism is the act of defacing or destroying computer equipment

• to help reduce the chances of the theft,companies and use a variety of security measures

For example
-physical access control 
-alarm system
-cables to lock equipment 
-real time location system
-password,possessed object,and biometrics 

Software Theft
software theft occurs when someone steals software media,intentionally erases programs, illegally copies a program and illegally registers and activates a program

A single-user license agreement typically contains the following conditions
Permitted to
-Install the software on one computer 
-make one copy of the software
-Remove the software from our computer before giving it away or selling it

Not permitted to
-Install the software on a network
-give copies to friends or while continuing to use the software 
-export the software
-rent or lease the software

• copying, loaning , borrowing , renting , or distributing software can be a violation of copyright law
• some software requires product activation to function fully

Information Theft
Information theft occurs when someone steals personal or confidential information

• Encryption is a process of converting readable data into unreadable characters to prevent unauthorized access
• a digital signature is an encrypted code that a person , wed site , or organization attaches to an electronic message to verify the identity of the sender
• Web browsers and Web sites use encryption techniques
• popular security techniques include digital certificates , transport layer security(TLS) , secure HTTP and VPN

System Failure

• A system failure is the prolonged malfunction of a computer 
• a variety of factors can lead to system failure including
• -aging hardware                                                                             -natural disasters                                                                           -electrical power problems                                                            -errors in computer programs
• two ways to protect from system failures cauesd by electrical power variations include surge protectors and uninterruptable power supplies (UPS)

Backing Up- The Ultimate Safeguard 

• a backup is a duplicate of a file , program , or disk that can be used if the original is lost , damaged or destroyed 
• Offsite  backups are stored in a location separate from the computer site
• two categories of backup - full backup , selective backup
• three-generation backup policy

Wireless Security 

• wireless access poses additional security risks -about 80 percent of wireless network have no security protection
• war driving  allows individual to detect wireless network while driving a vehicle through the area
• in additional to using firewall some safeguards improve security of wireless network
• -a wireless access point should not broadcast an SSID                -change the default SSID                                                              -configure a WAP so that only certain devices can access it        -use WPA or WPA2 security standards

Ethics and Society 

• Computer ethics are the moral guidelines that govern the use of computers and information systems.
• Information accuracy is a concern.
• Intellectual property rights are the rights to which creators are entitled for their work.
• An IT code of conduct is a written guideline that helps determine whether a specific computer action is ethical or unethical.
• Green Computing involves reducing the electricity and environmental waste while using a computer.
• Information privacy refers to the right of individuals and companies to deny or restrict the collection nad use of information about them.
• Huge databases store data online.
• It is important to safeguard your information.
• a cookie is a small text file that a web server stores on our computer
• spam is an unsolicited e-mail message or newsgroup posting
• E-mail filtering blocks e-mail messages from designated sources
• Anti-spam programs attempt to removes spam before it reaches our inbox
• Phishing is a scam in which a perpetrator sends an official looking e-mail message that attempts to obtain our personal and financial information 
• Pharming is a scam where a perpetrator attempts to obtain your personal and financial information via spoofing
• Content filtering is the process of restricting access to certain material on the Web
• Web filtering software restricts access to specified Wed sites

Chapter 10 Managing a Database

Database is a collection of data organized in a manner that allows access, retrieval, and use of that data.
Data is a collection of unprocessed item for example text , number , images , audio and video
Information is processed data

Database , Data and Information 

• Database software as we called a database management system (DBMS) it allow user to -create a computerized database                                                   -add,modify and delete data                                                         -sort and retrieve data                                                                   -create forms and reports from the                                                 data 
• Data integrity identifies the quality of the data 
• Garbage in ,garbage out(GIGO) points out the accuracy of a computer output depends on the accuracy of the input
• For information should have the following characteristic that is accurate , verifiable,timely,organized,accessible,useful andcost-effective

The Hierarchy of Data

• a character is one byte for the number , letters ,space punctuation marks or other symbols
• a field is a combination of one or more related characters for example field name , field size and data type
• common data types include text , numeric , AutoNumber , currency , date , memo , yes/no , hyperlink , object and attachment
• a record is a group of related fields-a primartkey uniquely identifies each record 
• a data file is a collection of related record

Maintaining Data

• File maintenance refers to the procedures that keep data current -adding records,modifying records and deleting records
• users add new records to a file when they obtain new data
• user modify a record to correct inaccurate data or update olad data
• Validation compares data with a set of rules or values to find out if the data is correct -alphabetic/numeric check ,range check , consistency check , completeness check , check digit and other checks

File processing Versus Databases 
File processing system

• each department has its own set of files 
• used for many years
• have data redundancy 
• isolate data

Database approach

• programs and users share data 
• reduce data redundancy
• improve data integrity 
• share data
• allows easier access
• reduces development time 
• can be more vulnerable

Database Management Systems

• a data dictionary contains data about each file in the database and each field in those files
• a DBMS provides several tools that allow user and programs to retrieve and maintain data in the database 
• a query language consists of simple , English -like statements that allow users to specify the data to display, print, or store
• query by example (QBE) provides a GUI to assist users with retrieving data
• A dorm is a window on the screen that provides areas for entering or modifying data in a database
• a report generator allows users to design a report on the screen , retrieve data into the report design , and then display or print the report
• A DMS provides means to ensure that only authorized users access data at permitted times - access privileges                                                                          -principle of least privilege
• A DMBS provides a variety of techniques to restore the database to a usable form in case it is damaged or destroyed         -backup          -log       -recovery utility     -continuous backup

Relational, object-Oriented, and multidimensional Databases

• a data model consists of rules and standards that define how the database organizes data
• A relational database stores data in tables that consist of row and columns .each row has a primary key and each column has a unique name
• 
  
• a relationship is a link within the data 
• structured query language (SQL) is a query language that allows users to manage, update,and retrieve data
• an object-oriented database (OODB) stores data in objects 
• examples of applications appropriate for an object-oriented database include multimedia database , groupware database , computer aided design database and hypertext database
• a multidimensional database can store data in more than two dimensions of data
• a data warehouse is a huge database that stores and manages the data required to analyze historical and current transactions

Wed Databases

• databases on the web allow you to

   -shop for products or                                                                              services

   -buy or sell stocks 

   -search for a job

   -make airline reservations

   -register for college classes

   -check semester grades

Database Administration 

• it is important have have a carefully designed database
• Database Analyst(DA)-decides on proper filed placement,defines data relationship ,and identifies users access privileges
• Database Administrator (DBA)-creates and maintains the data dictionary ,manages security , monitors performance and checks backup and recovery procedures
• Employees shold learn how to use the data in the database effectively-interact with database                                                                  -identify new data for the database                                              -maintain the database

Chapter 9 Network and Communications
Communications
Computer communications describes a process in whch two or more computers or devices transfer data, instructions,and information

(sending  device) - (communications channel)-( receiving device)

User of Computer Communications
user can send and receive wireless messages using wireless messaging services

1.Text messaging  (SMS) allows users to send and receive short text messages on a phone or other mobile device or computer

2.Picture messaging allows users to send pictures and sound files

3.Video messaging allows users to send short video clips

4.Wireless instant messaging allows wireless users to exchange real-time messages with one or more other users 

Wireless Internet access points allow people to connect wirelessly to the internet from home,work,school,and in many public locations

• 
  

A cybercafe is a location for people to use computer to access internet

A global positioning system (GPS) is a navigation system that consists of one or more earth-based receivers that accept and analyze signals sent by satellites in order tp determine the Gps receiver's geographic location

Groupware-helps groups of people work together on projects and                   share information over a network 
                  -Component of work group computing
                  -Major feature is a group scheduling
Voice mail-is allows someone to leave a voice message for one or                more people 
                  -computer in voice mail system converts an analog                       voice message into digital form
                  -a voice mailbox is a storage location on a hard disk int                he voice mail system
Many programs provide a means to collaborate, or work online ,with other users connected to a server
Collaboration software includes tools that enables users to share documents via online meeting and communicate with other connected users for example online meeting ,web conferences and document management systems
Web services enable programmers to create applications that communications with other remote computer over the Internal or on an internal business network 
A mashup is a web application that combines services from two or more sorces

Networks
A network is a collection of computers and devices connected together via communications devices and transmission media. Advantages of a network include: Facilitating communications, Sharing hardware and software, Transferring funds, Sharing data and information.
A local area network (LAN) is a network that connects computers and devices in a limited geographical area. A wireless LAN (WLAN) is a LAN that uses no physical wires. A metropolitan area network (MAN) connects LANs in a metropolitan area. A wide are network (WAN) is a network that covers a large geographical area.
The design of computers, devices, and media on a network is sometimes called the network architecture. P2P descirbes an Internet network on which users access each other's hard disks and exchange files directly over the Internet. A network topology refers to the layout of the computers and devices in a communications network. An intranet is an internal network that uses Internet technologies. An extranet allows customers or suppliers to access part of its intranet. 

Network Communications Standards
Ethernet is a network standard that specifies no computer controls when data can be transmitted. 
The token ring standard specifies that computers and  devices on the network share or pass a special (token). 
TCP/IP is a network standard that defines how messages are routed from one end of a network to another.
Wi-Fi identifies any network based on the 802.16 standard that facilitates wireless communication.
Sometimes referred to as wireless Ethernet.
Bluetooth defines how two Bluetooth devices use short-range radio waves to transmit data.
UWB (ultra-wideband) specifies how two UWB devices use short-range radio waves to communicate at high speeds.
IrDA transmits data wirelessly via infrared (IR) light waves.
RFID uses radio signals to communicate with a tag placed in or attached to an object, animal, or person.
Communications software consists of programs that: Helps users establish a connection to another computer or network. Manage the transmission of data, instructions, and information.

Communications Over the Telephone Network
The public switched telephone network (PSTN) is the worldwide telephone system.
A communicaation device is any type of hardware capable of transmitting data, instructionsm and information between a sending device and a receiving device.
A dial-up modem converts signals between analog and digital.
A digital modem sends and receives data and information to and from a digital line.
A wireless modem uses the cell phone network to connect to the Internet wirelessly from a notebook computer, a smart phone, or other mobile device.
A network card enables a computer or device to access a network.
Available in a variety of styles.
Wireless network cards often have an antenna.

Communications Devices
A wireless access point is a central communications device that allows computers and devices to transfer data wirelessly among themselves or to a wired network.
A router connects multiple computers or other routers together and transmits data to its correct destination on a network.
Many are protected by a hardware firewall.
A hub or switch connects several devices in a network together.

Home Networks
Home networks provide computers with the following capabilities: Connect to the Internet at the same times, Play multiplayer games, Connect game consoles to the Internet.

Communications Channel
the amount of data that can travel over a communications channel sometimes is called the bandwidth.
Latency is the time it takes a signal to travel from one location to another on a network.
Transmission media carries one or more signals.
Broadband media transmit multiple signals simultaneously.

Wireless Transmission Media
Cellular radio is a form of broadcast radio that is used widely for mobile communications.
Microwaves are radio waves that provide a high-speed signal transmission.
A communications satellite is a space station that receives microwave signals from an earth-based station, amplifies it, and broadcasts the signal over a wide area.

Chapter 8 Types of storage
Storage 
Storage its holds data,instructions and information for future use.
A storage medium is the physical material on which computer keeps data, instructions and information.

• Capacity is the number of bytes a storage medium can hold. For example kilobyte(KB) ,Megabyte (MB) ,Gigabyte (GB) ,Terabyte(TB) 
• a storage device is the computer hardware that records or retrieves items to and from storage media
• reading is the process of transferring items from a storage medium into memory
• writing is the process of transferring item from memory to a storage medium
• Access time measures the amount of time it takes a storage device to locate an item on a storage medium and the time required to deliver an item from memory to the processor

Hard disks

• a hard disk that contains one more inflexible , circular platters that use magnetic particles to store data , instructions , and information
• hard disk can store data by using longitudinal recording or perpendicular recording
• the characteristics of a hard disk include capacity ,platters,read/write heads ,cylinders , sectors and tracks ,revolutions per Minute ,transfer rate and access time
• Formatting is the process of diving the disk into tracks and sectors so that the operating system can store and locate data and information
• the hard disk arms move the read and write head which reads items and writes item in the drive
• A head crash occurs when a read and write head touches the surface of a platter 
• and always keep a backup of our hard disk
• RAIN is a group of two or more integrated hard disks
• A network attached storage (NAS) device is a server connected to a network with the sole purpose of providing storage 
• a disk controller consists of a special-purpose chip and electronic circuits that control the transfer of data,instructions,and information from a disk to and from the system bus and other components of the computer
• SATA , EIDE , SCSI , SAS

Flash Memory Storage

Flash memory chips are a type of solid state media and contain no moving parts

Solid state drives (SSDs)have several advantages over magnetic hard disk for example faster success time , faster transfer rates , generate less heat and consume less power and last longer 

• a memory card is a removable flash memory device that you insert and remove from a slot in a computer, mobile device , or card reader/writer for example compact flash (CF) ,secure digital (SD) , secure digital high capacity (SDHC) ,microSD , microSDHC ,picture card , memory stick and memory stick micri(M2)
• USB flash drives plug into a USB port on a computer or mobile device
• an Express Card module is a removable device that fits in an Express Card slot 
• Developed by the PCMCIA
• Commonly used in notebook computers

Cloud storage

cloud  storage is an Internet service that provides storage to computer users

Optical Discs

an optical disc consists of a flat,round,portable disc made of metal,plastic and lacquer that is written and read by a laser 

• it store software,data ,digital photos,movies and music
• it commonly store items in a single track that spirals from the center of the disc to the edge
• Track is divided into evenly sized sectors
• Archive disc-stores photo from online photo center                                         -resolution usually is 7200 pixels per photo                                 -cost is determined by the number of photos that                            being stored
• picture CD - single-session CD-ROM that stores digital                                   versions of film                                                                          -it uses a 1024 x 1536 resolution                                                  -many photo centers offer Picture CD dervices

Other types of storage 

• tape is a magnetically coated ribbon of pla stic capable of storing large amounts of data and information
• tape drive is reads and writes data and information on a tape
• a magnetic stripe card contains a magnetic sripe that stores information 
• a smart card stores data on a thin microprocessor embedded in the card
• Microfilm and microfiche store microscopic images of documents on a roll or sheet film