Chapter 10 Database Management

 The assignment from
Mr Tri Djoko Wahjono, Ir., M.Sc.  

 

1. What Is a Database, and How Does a Database Interact with Data and Information?

A database is a collection of data organized in a manner that allows access, retrieval, and use of that data. Database software, often called a database management system (DBMS), allows users to create a computerized database; add, modify, and delete the data; sort and retrieve the data; and create forms and reports from the data. Data is a collection of unprocessed items, which can include text, numbers, images, audio, and video. Computers process data into information. Information is processed data; that is, it is organized, meaningful, and useful. In addition to documents, information can be in the form of audio, images, and video.

2. What Is Data Integrity, and What Are the Qualities of Valuable Information?

Because data is used to generate information, many organizations realize that data is one of their more valuable assets. Data integrity identifies the quality of data. Data integrity is important because computers and people use information to make decisions and take actions. For a computer to produce correct information, the data that is entered in a database must have integrity. For information to be valuable, it should be accurate, verifiable, timely, organized, accessible, useful, and cost-effective. Accurate information is error free. Verifiable information can be proven as correct or incorrect. Timely information has an age suited to its use. Organized information is arranged to suit the needs and requirements of the decision maker. Accessible information is available when the decision maker needs it. Useful information has meaning to the person who receives it. Cost-effective information should give more value than it costs to produce.

3. What Is Meant by Character, Field, Record, and File?

Data is classified in a hierarchy, with each level of data consisting of one or more items from the lower level. A bit is the smallest unit of data a computer can process. Eight bits grouped together in a unit form a byte, and each byte represents a single character, which can be a number, letter, space, punctuation mark, or other symbol. A field is a combination of one or more related characters or bytes and is the smallest unit of data a user accesses. A record is a group of related fields. A data file is a collection of related records stored on a storage medium such as a hard disk or optical disc.

4. What Are File Maintenance Techniques and Validation Techniques?

File maintenance refers to the procedures that keep data current. File maintenance procedures include adding records when new data is obtained, modifying records to correct inaccurate data or to update old data with new data, and deleting records when they no longer are needed. Validation is the process of comparing data with a set of rules or values to find out if the data is correct. Many programs perform a validity check that analyzes data, either as you enter it or after you enter it, to help ensure that it is correct. Types of validity checks include an alphabetic check, a numeric check, a range check, a consistency check, a completeness check, and a check digit.

5. How Is a File Processing Approach Different from the Database Approach?

In a file processing system, each department or area within an organization has its own set of data fi les. The records in one fi le may not relate to the records in any other fi le. Two major weaknesses of fi le processing systems are redundant data (duplicated data) and isolated data. With a database approach, many programs and users share the data in a database. The database approach reduces data redundancy, improves data integrity, shares data, permits easier access, and reduces development time. A database, however, can be more complex than a fi le processing system, requiring special training and more computer memory, storage, and processing power than fi le processing systems. Data in a database also can be more vulnerable than data in fi le processing systems.

6. What Functions Are Common to Most Database Management Systems?

Database management systems (DBMSs) are available for many sizes and types of computers. Whether designed for a small or large computer, most DBMSs perform common functions. A data dictionary, sometimes called a repository, contains data about each fi le in the database and each field in those fi les. A DBMS offers several methods to retrieve and maintain data in the database, such as query languages, query by example, forms, and report generators. 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) has a graphical user interface that assists users with retrieving data. A form, sometimes called a data entry form, is a window on the screen that provides areas for entering or modifying data in a database. A report generator, also called a report writer, allows users to design a report on the screen, retrieve data into the report design, and then display or print the report. To supply security, most DBMSs can identify different levels of access privileges that define the actions a specific user or group of users can perform for each field in a database. If a database is damaged or destroyed, a DBMS provides techniques to return the database to a usable form. A backup is a copy of the database. A log is a listing of activities that modify the contents of the database. A recovery utility uses the logs and/or backups to restore the database using rollforward or rollback techniques. In a rollforward, also called forward recovery, the DBMS uses the log to reenter changes made to the database since the last save or backup. In a rollback, also called backward recovery, the DBMS uses the log to undo any changes made to the database during a certain period. Continuous backup is a backup plan in which all data is backed up whenever a change is made.

7. What Are Characteristics of Relational, Object-Oriented, and Multidimensional Databases?

A data model consists of rules and standards that define how the database organizes data. Three popular data models are relational, object-oriented, and multidimensional. A relational database stores data in tables that consist of rows and columns. A relational database developer refers to a fi le as a relation, a record as a tuple, and a field as an attribute. A relational database user refers to a fi le as a table, a record as a row, and a field as a  column. A relationship is a link within the data in a relational database. Structured Query Language (SQL) allows users to manage, update, and retrieve data in a relational database. An object-oriented database (OODB) stores data in objects. An object is an item that contains data, as well as the actions that read or process the data. Applications appropriate for an object-oriented database include a multimedia database, a groupware database, a computer-aided design (CAD) database, a hypertext database, and a hypermedia database. Object-oriented databases often use an object query language (OQL) to manipulate and retrieve data. A multidimensional database stores data in dimensions. These multiple dimensions, sometimes known as a hypercube, allow users to access and analyze any view of the database data. No standard query language exists for multidimensional databases. One application that uses multi dimensional databases is a data warehouse, which is a huge database that stores and manages the data required to analyze historical and current transactions. A smaller version of a data warehouse is the data mart, which contains a database that helps a specific group or department make decisions.

8. How Are Web Databases Accessed?

To access data in a Web database, you fill in a form or enter search text on a Web page, which is the front end to the database. A Web database usually resides on a database server, which is a computer that stores and provides access to a database. One type of program that manages the sending and receiving of data between the front end and the database server is a CGI (Common Gateway Interface) script.

9. What Are the Responsibilities of Database Analysts and Administrators?

A database analyst (DA), or data modeler, focuses on the meaning and usage of data. The DA decides on the placement of fields, defines data relationships, and identifies users’ access privileges. A database administrator (DBA) requires a more technical inside view of the data. The DBA creates and maintains the data dictionary, manages database security, monitors database performance, and checks backup and recovery procedures. In small companies, one person often is both the DA and DBA. In larger companies, the responsibilities of the DA and DBA are split among two or more people.

Chapter 9 Communications and Networks

  The assignment from
Mr Tri Djoko Wahjono, Ir., M.Sc. 

1. What Is the Purpose of the Components Required for Successful Communications, and What Are Various Sending and Receiving Devices?

Computer communications describes a process in which two or more computers or devices transfer data, instructions, and information. Successful communications requires a sending device that initiates a transmission instruction, a communications device that connects the sending device to a communications channel, a communications channel on which the data travels, a communications device that connects the communications channel to a receiving device, and a receiving device that accepts the transmission of data, instructions, or information. All types of computers and mobile devices serve as sending and receiving devices in a communications system.

2. How Are Computer Communications Used?

Communications technologies include blogs, chat rooms, e-mail, fax, FTP, instant messaging, newsgroups, RSS, video conferencing, VoIP, Web, Web folders, and wikis. Users can send and receive wireless messages to and from smart phones, cell phones, handheld game consoles, and other mobile devices using text messaging, picture messaging and video messaging, and wireless instant messaging. People connect wirelessly to the Internet through a wireless Internet access point. A hot spot is a wireless network that provides Internet connections to mobile computers and devices. A cybercafé is a coffeehouse, restaurant, or other location that provides computers with Internet access. A global positioning system (GPS) analyzes signals sent by satellites to determine an earth-based receiver’s geographic location. Many software products provide a means to collaborate, or work online with other users connected to a server. Groupware is software that helps groups of people work on projects or share information over a network. Voice mail allows someone to leave a voice message for one or more people. Web services describe standardized software that enables programmers to create applications that communicate with other remote computers.

3. What Are the Advantages of Using a Network, and How Are LANs, MANs, and WANs Different?

A network is a collection of computers and devices connected together via communications devices and transmission media. Advantages of using a network include facilitating communications, sharing hardware, sharing data and information, sharing software, and transferring funds. Networks typically are classified as a local area network (LAN ), which connects computers in devices in a limited geographical area; a metropolitan area network (MAN ), which is a high-speed network that connects local area networks in a larger area, such as city or town; or a wide area network ( WAN ), which covers a large geographic area using a communications channel that combines many types of media.

4. How Are a Client/Server and Peer-to-Peer Networks Different, and How Does a P2P Network Work?

On a client/server network, one or more computers acts as a server, sometimes called a host computer, which controls access to network resources and provides a centralized storage area, while the other computers and devices on the network are clients that rely on the server for resources. A peer-to-peer network is a simple network that typically connects fewer than 10 computers that have equal responsibilities and capabilities. P2P is an Internet peer-to-peer network on which users access each other’s hard disks directly and exchange fi les over the Internet.

5. How Are a Star Network, Bus Network, and Ring Network Different?

A network topology refers to the layout of computers and devices in a communications network. Three commonly used network topologies are the star, bus, and ring. On a star network, all computers and devices on the network connect to a central device, thus forming a star. A bus network consists of a single central cable to which all computers and other devices connect. On a ring network, a cable forms a closed loop (ring) with all computers and devices arranged along the ring.

6. What Are Various Network Communications Standards?

A network standard defines guidelines that specify the way computers access a medium, the type(s) of medium, the speeds on different types of networks, and the type of physical cable or wireless technology used. Network communications standards include the following. Ethernet specifi es that no central computer or device on the network should control when data can be transmitted. Token ring requires devices to share or pass a special signal, called a token. TCP/IP divides data into packets. Wi-Fi identifies any network based on the 802.11 standards for wireless communications. Bluetooth uses short-range radio waves to transmit data. UWB specifies how two UWB devices use short-range radio waves to communicate at high speeds. IrDA transmits data wirelessly via infrared light waves. RFID uses radio signals for communications. WiMAX is a network standard developed by IEEE that specifies how wireless devices communicate over the air in a wide area. The Wireless Application Protocol (WAP) specifies how some mobile devices can display Internet content.

7. What Is the Purpose of Communications Software?

Communications software helps users establish a connection to another computer or network; manages the transmission of data, instructions, and information; and provides an interface for users to communicate with one another.

8. What Are Various Types of Lines for Communications over the Telephone Network?

The telephone network uses dial-up lines or dedicated lines. A dial-up line is a temporary connection that uses one or more analog telephone lines for communications. A dedicated line is an always-on connection established between two communications devices. Dedicated lines include the following. ISDN is a set of standards for digital transmission of data over standard copper telephone lines. DSL transmits at fast speeds on existing standard copper telephone wiring. FTTP, or Fiber to the Premises, uses fiber-optic cable to provide extremely high-speed Internet access to a user’s physical permanent location. Two specific types of FTTP are FTTH (Fiber to the Home) and FTTB (Fiber to the Building). A T-carrier line is a long-distance digital telephone line that carries multiple signals over a single communications line. ATM is a service that carries voice, data, video, and multimedia at extremely high speeds.

9. What Are Commonly Used Communications Devices?

A communications device is hardware capable of transmitting data between a sending device and a receiving device. A dial-up modem converts digital signals to analog signals and analog signals to digital signals so that data can travel along analog telephone lines. A digital modem sends and receives data and information to and from a digital line. An ISDN modem transmits digital data to and from an ISDN line, while a DSL modem transmits digital data to and from a DSL line. A cable modem, sometimes called a broadband modem, is a digital modem that sends and receives digital data over the cable television network. A wireless modem uses the cell phone network to connect to the Internet wirelessly from mobile computers and devices. A network card enables a computer or device that does not have built-in networking capability to access a network. A wireless access point allows computers and devices to transfer data wirelessly. A router connects multiple computers or other routers together and transmits data to its correct destination on the network. A hub or switch is a device that provides a central point for cables in a network.

10. How Can a Home Network Be Set Up?

A home network connects multiple computers and devices in a home. An Ethernet network connects each computer to a hub with a physical cable. A home powerline cable network uses the same lines that bring electricity into the house.A phoneline network uses existing telephone lines in a home. Most home networks use a Wi-Fi network.

11. What Are Various Physical and Wireless Transmission Media?

Transmission media consist of materials or substances capable of carrying one or more signals. Physical transmission media use tangible materials to send communications signals. Twisted-pair cable consists of one or more twisted-pair wires bundled together. Coaxial cable consists of a single copper wire surrounded by at least three layers: an insulating material, a woven or braided metal, and a plastic outer coating. Fiber-optic cable consists of thin strands of glass or plastic that use light to transmit signals. Wireless transmission media send communications signals through the air or space. Infrared (IR) sends signals using infrared light waves. Broadcast radio distributes radio signals through the air over long and short distances. Cellular radio is a form of broadcast radio that is used widely for mobile communications. Microwaves are radio waves that provide a highspeed signal transmission. A communications satellite is a space station that receives microwave signals from an earth-based station, amplifies the signals, and broadcasts the signals back over a wide area.

Chapter 8 Operating System and Utility Programs

 The assignment from
Mr Tri Djoko Wahjono, Ir., M.Sc. 

1. What Is System Software, and What Are the Two Types of System Software?

System software consists of the programs that control or maintain the operations of a computer and its devices. Two types of system software are operating systems and utility programs. An operating system (OS) is a set of programs containing instructions that work together to coordinate all the activities among computer hardware resources. A utility program, also called a utility, performs maintenance-type tasks, usually related to managing a computer, its devices, or its programs.

2. What Are the Functions of an Operating System?

The operating system starts and shuts down a computer, provides a user interface, manages programs, manages memory, coordinates tasks, configures devices, establishes an Internet connection, monitors performance, provides utilities, updates automatically, controls a network, and administers security. The user interface controls how data and instructions are entered and how information is displayed on the screen. Two types of user interfaces are a graphical user interface (GUI ) and a command-line interface. Managing programs refers to how many users, and how many programs, an operating system can support at one time. An operating system can be single user/single tasking, single user/multitasking, multiuser, or multiprocessing. Memory management optimizes the use of random access memory (RAM). If memory is insufficient, the operating system may use virtual memory, which allocates a portion of a storage medium to function as additional RAM. Coordinating tasks determines the order in which tasks are processed. Tasks include receiving data from an input device, processing instructions, sending information to an output device, and transferring items between storage and memory. Configuring devices involves loading each device’s driver when a user boots the computer. A driver, short for device driver, is a small program that tells the operating system how to communicate with a specific device. Establishing an Internet connection sets up a connection between a computer and an Internet access provider. A performance monitor is an operating system program that assesses and reports information about computer resources and devices. Operating systems often provide the capability of managing and searching for fi les, viewing images, securing a computer from unauthorized access, uninstalling programs, and other tasks. Most operating systems also include an automatic update feature that provides updates to the program. A server operating system is an operating system that organizes and coordinates how multiple users access and share network resources. Network administrators typically have an administrator account that enables them to access fi les, install programs, and specify network settings, including creating user accounts and establishing permissions.

3. What Is the Startup Process on a Personal Computer?

Booting is the process of starting or restarting a computer. When a user turns on a computer, the power supply sends a signal to the system unit. The processor chip finds the ROM chip(s) that contains the BIOS (basic input/output system), which is firmware with the computer’s startup instructions. The BIOS performs the power-on self test (POST ) to check system components and compares the results with data in a CMOS chip. If the POST completes successfully, the BIOS searches for the system files and the kernel of the operating system, which manages memory and devices, and loads them into memory from storage. Finally, the operating system loads configuration information, requests any necessary user information, and displays the desktop on the screen. The operating system executes programs in the Startup folder, which contains a list of programs that open automatically when you boot the computer.

4. What Are Features of Windows 7, Mac OS X, UNIX, and Linux Operating Systems?

A stand-alone operating system is a complete operating system that works on a desktop computer, notebook computer, or mobile computing device. Windows 7 is Microsoft’s fastest, most efficient operating system to date, offering quicker program start up, built-in diagnostics, automatic recovery, improved security, p y enhanced searching and organizing capabilities, and an easy-to-use interface. Most users choose from Windows 7 Starter, Windows 7 Home Premium, Windows 7 Ultimate, or Windows 7 Professional editions. Mac OS X is a multitasking operating system available only for Apple computers. UNIX is a multitasking operating system developed at Bell Laboratories. Linux is a popular, multitasking UNIX-type operating system that is open source software, which means its code is available to the public for use, modification, and redistribution.

5. What Are Various Server Operating Systems?

Server operating systems include Windows Server 2008, UNIX, Linux, Solaris, and NetWare. Windows Server 2008 is an upgrade to Windows Server 2003 and includes features of previous Windows Server versions. UNIX, like Linux, is a multipurpose operating system because it is both a stand-alone and server operating system. Solaris, a version of UNIX developed by Sun Microsystems, is a server operating system designed specifically for e-commerce applications. Novell’s NetWare is a server operating system designed for client/server networks.

6. What Are the Features of Several Embedded Operating Systems?

Mobile devices and many consumer electronics have an embedded operating system that resides on a ROM chip. Popular embedded operating systems include Windows Embedded CE, Windows Mobile, Palm OS, iPhone OS, BlackBerry, Google Android, embedded Linux, and Symbian OS. Windows Embedded CE is a scaled-down Windows operating system designed for use on communications, entertainment, and computing devices with limited functionality. Windows Mobile, an operating system based on Windows Embedded CE, provides a user interface designed for specific types of smart phones and PDAs. Palm OS is an operating system used on smart phones and PDAs. iPhone OS, developed by Apple, is an operating system for the iPhone and iPod touch. The BlackBerry operating system runs on handheld devices supplied by RIM. Google Android is an operating system developed by Google for mobile devices. Embedded Linux is a scaled-down Linux operating system for smart phones, PDAs, portable media players, and other devices requiring an embedded operating system. Symbian OS is an open source multitasking operating system designed for smart phones.

7. What Is the Purpose of Several Utility Programs?

Most operating systems include several built-in utility programs. A file manager performs functions related to fi le management. A search utility attempts to locate a fi le on your computer based on criteria you specify. An image viewer displays, copies, and prints the contents of a graphics fi le, such as photos. An uninstaller removes a program and any associated entries in the system fi les. A disk cleanup utility searches for and removes unnecessary files. A disk defragmenter reorganizes the fi les and unused space on a computer’s hard disk. A backup utility is used to copy, or back up, selected fi les or an entire hard disk to another storage medium. A restore utility reverses the backup process and returns backed up fi les to their original form. A screen saver displays a moving image or blank screen if no keyboard or mouse activity occurs for a specified time. A personal firewall detects and protects a personal computer from unauthorized intrusions. An antivirus program protects computers against a virus, or potentially damaging computer program, by identifying and removing any computer viruses. A spyware remover detects and deletes spyware and other similar programs. An adware remover detects and deletes adware. Internet filter programs can include Web filtering software, an anti-spam program, a phishing filter, and a pop-up blocker. A file compression utility shrinks the size of a fi le so that it takes up less storage space. A media player allows you to view images and animation, listen to audio, and watch video fi les on a computer. Disc burning software writes text, graphics, audio, and video fi les on a recordable or rewritable CD, DVD, or Blu-ray Disc. A personal computer maintenance utility identifies and fixes operating system problems and improves a computer’s performance.