Saturday, December 14, 2013

Chapter 10

Name : Genesius Hartanto
NIM : 1701308971
Class : 01PCT
Professor : 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 an organized collection of data. The data are typically organized to model relevant aspects of reality in a way that supports processes requiring this information. For example, modeling the availability of rooms in hotels in a way that supports finding a hotel with vacancies.
Database management systems (DBMSs) are specially designed applications that interact with the user, other applications, and the database itself to capture and analyze data. A general-purpose database management system (DBMS) is a software system designed to allow the definition, creation, querying, update, and administration of databases. Well-known DBMSs include MySQL, PostgreSQL, SQLite, Microsoft SQL Server, Oracle, SAP, dBASE, FoxPro, IBM DB2, LibreOffice Base and FileMaker Pro. A database is not generally portable across different DBMS, but different DBMSs can interoperate by using standards such as SQL and ODBC or JDBC to allow a single application to work with more than one database.

Formally, the term "database" refers to the data itself and supporting data structures. Databases are created to operate large quantities of information by inputting, storing, retrieving, and managing that information. Databases are set up so that one set of software programs provides all users with access to all the data.
A "database management system" (DBMS) is a suite of computer software providing the interface between users and a database or databases. Because they are so closely related, the term "database" when used casually often refers to both a DBMS and the data it manipulates.
Outside the world of professional information technology, the term database is sometimes used casually to refer to any collection of data (perhaps a spreadsheet, maybe even a card index). This article is concerned only with databases where the size and usage requirements necessitate use of a database management system.
The interactions catered for by most existing DBMS fall into four main groups:
·         Data definition. Defining new data structures for a database, removing data structures from the database, modifying the structure of existing data.
·         Update. Inserting, modifying, and deleting data.
·         Retrieval. Obtaining information either for end-user queries and reports or for processing by applications.
·         Administration. Registering and monitoring users, enforcing data security, monitoring performance, maintaining data integrity, dealing with concurrency control, and recovering information if the system fails.
A DBMS is responsible for maintaining the integrity and security of stored data, and for recovering information if the system fails.
Both a database and its DBMS conform to the principles of a particular database model. "Database system" refers collectively to the database model, database management system, and database.
Physically, database servers are dedicated computers that hold the actual databases and run only the DBMS and related software. Database servers are usually multiprocessor computers, with generous memory and RAID disk arrays used for stable storage. RAID is used for recovery of data if any of the disks fails. Hardware database accelerators, connected to one or more servers via a high-speed channel, are also used in large volume transaction processing environments. DBMSs are found at the heart of most database applications. DBMSs may be built around a custom multitasking kernel with built-in networking support, but modern DBMSs typically rely on a standard operating system to provide these functions. Since DBMSs comprise a significant economical market, computer and storage vendors often take into account DBMS requirements in their own development plans.
Databases and DBMSs can be categorized according to the database model(s) that they support (such as relational or XML), the type(s) of computer they run on (from a server cluster to a mobile phone), the query language(s) used to access the database (such as SQL or XQuery), and their internal engineering, which affects performance, scalability, resilience, and security.
2.       What is Data Integrity, and what are the qualities of valuable information?
Data integrity refers to maintaining and assuring the accuracy and consistency of data over its entire life-cycle, and is a critical aspect to the design, implementation and usage of any system which stores, processes or retrieves data. The term data integrity is broad in scope and may have widely different meanings depending on the specific context - even under the same general umbrella of computing. This article provides only a broad overview of some of the different types and concerns of data integrity.
Data integrity is the opposite of data corruption, which is a form of data loss. The overall intent of any data integrity technique is the same: ensure data is recorded exactly as intended (such as a database correctly rejecting mutually exclusive possibilities,) and upon later retrieval, ensure the data is the same as it was when it was originally recorded. In short, data integrity aims to prevent unintentional changes to information. Data integrity is not to be confused with data security, the discipline of protecting data from unauthorized parties.
Any unintended changes to data as the result of a storage, retrieval or processing operation, including malicious intent, unexpected hardware failure, and human error, is failure of data integrity. If the changes are the result of unauthorized access, it may also be a failure of data security. Depending on the data involved this could manifest itself as benign as a single pixel in an image appearing a different color than was originally recorded, to the loss of vacation pictures or a business-critical database, to even catastrophic loss of human life in a Life-critical system.

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 an 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 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 database approach?
Each department or area within an organization has its own set of data files. The records in one file may not relate to the records in any other file. Two major weaknesses of file processing systems are redundant data (duplicated data) and isolated data. With a database approach, many programs and users share the data in 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 file processing system, requiring special training and more computer memory, storage, and processing power than file processing systems. Data in a database also can be more vulnerable than data in file processing systems.

6.       What functions are common to most database management systems?
Database management system - (DBMS) A suite of programs which typically manage large structured sets of persistent data, offering ad hoc query facilities to many users. They are widely used in business applications.

A database management system (DBMS) can be an extremely complex set of software programs that controls the organization, storage and retrieval of data (fields, records and files) in a database. It also controls the security and integrity of the database. The DBMS accepts requests for data from the application program and instructs the operating system to transfer the appropriate data.

When a DBMS is used, information systems can be changed much more easily as the organization's information requirements change. New categories of data can be added to the database without disruption to the existing system.

Data security prevents unauthorized users from viewing or updating the database. Using passwords, users are allowed access to the entire database or subsets of the database, called subschemas (pronounced "sub-skeema"). For example, an employee database can contain all the data about an individual employee, but one group of users may be authorized to view only payroll data, while others are allowed access to only work history and medical data.

The DBMS can maintain the integrity of the database by not allowing more than one user to update the same record at the same time. The DBMS can keep duplicate records out of the database; for example, no two customers with the same customer numbers (key fields) can be entered into the database.

Query languages and report writers allow users to interactively interrogate the database and analyze its data.

If the DBMS provides a way to interactively enter and update the database, as well as interrogate it, this capability allows for managing personal databases. However, it may not leave an audit trail of actions or provide the kinds of controls necessary in a multi-user organization. These controls are only available when a set of application programs are customized for each data entry and updating function.

A business information system is made up of subjects (customers, employees, vendors, etc.) and activities (orders, payments, purchases, etc.). Database design is the process of deciding how to organize this data into record types and how the record types will relate to each other. The DBMS should mirror the organization's data structure and process transactions efficiently.

Organizations may use one kind of DBMS for daily transaction processing and then move the detail onto another computer that uses another DBMS better suited for random inquiries and analysis. Overall systems design decisions are performed by data administrators and systems analysts. Detailed database design is performed by database administrators.

The three most common organizations are the hierarchical database, network database and relational database. A database management system may provide one, two or all three methods. Inverted lists and other methods are also used. The most suitable structure depends on the application and on the transaction rate and the number of inquiries that will be made.

Database machines are specially designed computers that hold the actual databases and run only the DBMS and related software. Connected to one or more mainframes via a high-speed channel, database machines are used in large volume transaction processing environments. Database machines have a large number of DBMS functions built into the hardware and also provide special techniques for accessing the disks containing the databases, such as using multiple processors concurrently for high-speed searches.

The world of information is made up of data, text, pictures and voice. Many DBMSs manage text as well as data, but very few manage both with equal proficiency. Throughout the 1990s, as storage capacities continue to increase, DBMSs will begin to integrate all forms of information. Eventually, it will be common for a database to handle data, text, graphics, voice and video with the same ease as today's systems handle data.

7.       What are Characteristics of relational, object-oriented, and multidimensional databases?
This isn’t the first time in recent history that new types of database products have emerged and overcome RDBMS inefficiencies. Back in the 1980s, a class of applications was identified in which RDBMS products ill-handled the data-management needs (especially the generation of RDBMSs available at that time).
These applications all needed user-specified data types that varied among different implementations. For example, computer-aided design/computer-aided manufacturing (CAD/CAM) applications had to be capable of specifying data types that related to product drawings, blueprints, and other related factors.
Computer-aided software engineering (CASE) needed data types to represent applications and systems, databases, graphical representations of entities and attributes, process and data flows, and other parts of the application-development process.
What resulted was object-oriented database management systems (ODBMSs), which eliminated the table-row-column structures of relational databases and instead introduced the concepts of classes and subclasses (or types and subtypes), objects, properties, methods, and the other parts of object-oriented technology directly into the database engine.
Because RDBMS technology wasn’t well-suited to multidimensional analysis, particularly in terms of performance, vendors set out to develop their own structures tuned and optimized for improved performance.
If you track happenings in the database management world, you’re probably familiar with the convergence of relational and object-oriented database technology. RDBMS products are being equipped with object-oriented extensions.
Arguably, this approach to handling complex data types (objects) has won out over non-relational products (“pure” ODBMSs), primarily because of the large installed base of relational products and applications running on top of them. Will the same thing happen in the data warehousing world — relational technology overtaking and then overwhelming specialized multidimensional products? Only time will tell.

8.       How are Web Databases Accessed?
You can use Access 2010 and Access Services, a new component of SharePoint, to build web database applications. This helps you:
·         Secure and manage access to your data
·         Share data throughout an organization, or over the Internet
Note    A user account is required to use a web database. Anonymous access is not supported.
·         Create database applications that don't require Access to use

9.       What are the responsibilities of Database Analysts and Administrators?
A database administrator's responsibilities can include the following tasks:
·         Installing and upgrading the database server and application tools
·         Allocating system storage and planning future storage requirements for the database system
·         Modifying the database structure, as necessary, from information given by application developers verbally
·         Enrolling users and maintaining system security
·         Ensuring compliance with database vendor license agreement
·         Controlling and monitoring user access to the database
·         Monitoring and optimizing the performance of the database
·         Planning for backup and recovery of database information
·         Maintaining archived data
·         Backing up and restoring databases
·         Contacting database vendor for technical support
·         Generating various reports by querying from database as per need.

Chapter 9

Name : Genesius Hartanto
NIM : 1701308971
Class : 01PCT
Professor : 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. Today, even the smallest computers and devices can communicate directly with one another, with hundreds of computers on a company network, or with millions of other computers.
For successful communications, you need the following:
• A sending device that initiates an instruction to transmit data, instructions, or information.
• A communications device that connects the sending device to a communications channel.
• A communications channel, or transmission media on which the data, instructions, or information travel.
• A communications device that connects the communications channel to a receiving device.
• A receiving device that accepts the transmission of data, instructions, or information.
Some devices that serve as sending devices and receiving devices are
(a) mainframe computers,
(b) servers,
(c) desktop computers,
(d) notebook computers,
(e) smart phones,
(f) Internet-enabled portable media players,
(g) handheld game consoles, and
(h) GPS receivers.
The communications channel consists of telephone and power lines, cable television and other underground lines, microwave stations, and satellites.

2.     How Are Computer Communications Used?
Computer communications are everywhere. Many require that users subscribe to an Internet access provider. With other computer communications, an organization such as a business or school provides communications services to employees, students, or customers.
The following pages discuss a variety of computer communications. 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 cybercaf√© 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. Many businesses network their computers together to facilitate communications, share hardware, share data and information, share software, and transfer funds.
• Facilitating communications — Using a network, people communicate efficiently and easily via e-mail, instant messaging, chat rooms, blogs, wikis, online social networks, video telephone calls, online meetings, video conferencing, VoIP, wireless messaging services, and groupware.
• Sharing hardware — In a networked environment, each computer on the network can have access to hardware on the network. Business and home users network their hardware to save money.
• Sharing data and information — In a networked environment, any authorized computer user can access data and information stored on other computers on the network.
• Sharing software — Users connected to a network have access to software on the network.
To support multiple users’ access of software, most vendors sell network versions or site licenses of their software, which usually cost less than buying individual copies of the software for each computer.
• Transferring funds — Called electronic funds transfer (EFT ), it allows users connected to a network to transfer money from one bank account to another via transmission media.
LANs, MANs, and WANs
Networks usually are classified as a local area network, metropolitan area network, or wide area network. The main differentiation among these classifications is their area of coverage.
·         LAN (local area network) is a network that connects computers and devices in a limited geographical area such as a home, school computer laboratory, office building, or closely positioned group of buildings. Each computer or device on the network, called a node, often shares resources such as printers, large hard disks, and programs.Often, the nodes are connected via cables.
·         MAN (metropolitan area network) is a high-speed network that connects local area networks in a metropolitan area such as a city or town and handles the bulk of communications activity across that region. A MAN typically includes one or more LANs, but covers a smaller geographic area than a WAN. A MAN usually is managed by a consortium of users or by a single network provider that sells the service to the users. Local and state governments, for example, regulate some MANs. Telephone companies, cable television operators, and other organizations provide users with connections to the MAN.
·         WAN (wide area network) is a network that covers a large geographic area (such as a city, country, or the world) using a communications channel that combines many types of media such as telephone lines, cables, and radio waves (Figure 9-12). A WAN can be one large network or can consist of two or more LANs connected together. The Internet is the world’s largest WAN.

4.     How Are a Client/Server and Peer-to-Peer Network Different, and How Does a P2P Network Work?
·         Client/Server
On a client/server network, one or more computers act as a server, and the other computers on the network request services from the server. A server, sometimes called a host computer, controls access to the hardware, software, and other resources on the network and provides a centralized storage area for programs, data, and information. The clients are other computers and mobile devices on the network that rely on the server for its resources. For example, a server might store a database of customers. Clients on the network (company employees) access the customer database on the server.
·         Peer-to-Peer
One type of peer-to-peer network is a simple, inexpensive network that typically connects fewer than 10 computers. Each computer, called a peer, has equal responsibilities and capabilities, sharing hardware (such as a printer), data, or information with other computers on the peer-to-peer network. Each computer stores files on its own storage devices. Thus, each computer on the network contains both the server operating system and application software. All computers on the network share any peripheral device(s).attached to any computer. For example, one computer may have a laser printer and a scanner, while another has an ink-jet printer and an external hard disk. Peer-to-peer networks are ideal for very small businesses and home users.
·         Another type of peer-to-peer, called P2P, describes an Internet network on which users access each other’s hard disks and exchange files directly over the Internet. This type of peer-to peer network sometimes is called a file sharing network because users with compatible software and an Internet connection copy files from someone else’s hard disk to their hard disks. As more users connect to the network, each user has access to shared files on other users’ hard disks. When users log off the network, others no longer have access to their hard disks.

5.     How Are a Star Network, Bus Network, and Ring Network Different?
·         Star Network
On a star network, all of the computers and devices (nodes) on the network connect to a central device, thus forming a star. Two types of devices that provide a common central connection point for nodes on the network are a hub and a switch. All data that transfers from one node to another passes through the hub or switch. Star networks are fairly easy to install and maintain. Nodes can be added to and removed from the network with little or no disruption to the network. On a star network, if one node fails, only that node is affected. The other nodes continue to operate normally. If the hub or switch fails, however, the entire network is inoperable until the device is repaired. Most large star networks, therefore, keep backup hubs or switches available in case the primary one fails.
·         Bus Network
A bus network consists of a single central cable, to which all computers and other devices connect. The bus is the physical cable that connects the computers and other devices. The bus in a bus network transmits data, instructions, and information in both directions. When a sending device transmits data, the address of the receiving device is included with the transmission so that the data is routed to the appropriate receiving device. Bus networks are popular on LANs because they are inexpensive and easy to install. One advantage of the bus network is that computers and other devices can be attached and detached at any point on the bus without disturbing the rest of the network.
·         Ring Network
On a ring network, a cable forms a closed loop (ring) with all computers and devices arranged along the ring. Data transmitted on a ring network travels from device to device around the entire ring, in one direction. When a computer or device sends data, the data travels to each computer on the ring until it reaches its destination. If a computer or device on a ring network fails, the entire network potentially could stop functioning. A ring network can span a larger distance than a bus network, but it is more difficult to install. The ring topology primarily is used for LANs, but also is used in WANs.

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 specifies 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 consists of programs that (1) help users establish a connection to another computer or network; (2) manage the transmission of data, instructions, and information; and (3) provide an interface for users to communicate with one another. The first two are system software and the third is application software. Chapter 3 presented a variety of examples of application software for communications: e-mail, FTP, Web browser, newsgroup/message boards, chat rooms, instant messaging, video conferencing, and VoIP. Sometimes, communications devices are preprogrammed to accomplish communications tasks. Other communications devices require separate communications software to ensure proper transmission of data. Communications software works with the network standards and protocols just discussed to ensure data moves through the network or the Internet correctly. Communications software usually is bundled with the operating system or purchased network devices. 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?
·         Dial-Up Lines
A dial-up line is a temporary connection that uses one or more analog telephone lines for communications. A dial-up connection is not permanent. a dial-up line to connect computers costs no more than making a regular telephone call.
·         Dedicated Lines
Satellite local access area local telephone company A dedicated line is a type of always on connection that is established between two communications devices (unlike a dial-up line where the connection is reestablished each time it is used). The quality and consistency of the  connection on a dedicated line are better than a dial-up line because dedicated lines provide a constant connection. Businesses often use dedicated lines to connect geographically distant offices. Dedicated lines can be either analog or digital. Digital lines increasingly are connecting home and business users to networks around the globe because they transmit data and information at faster rates than analog lines. Five types of digital dedicated lines are ISDN lines, DSL, FTTP, T-carrier lines, and ATM.
·         ISDN Lines
For the small business and home user, an ISDN line provides faster transfer rates than dial-up telephone lines. Not as widely used today as in the past, ISDN (Integrated Services Digital Network) is a set of standards for digital transmission of data over standard copper telephone lines. With ISDN, the same telephone line that could carry only one computer signal now can carry three or more signals at once through the same line, using a technique called multiplexing.
·         DSL
DSL is a popular digital line alternative for the small business or home user. DSL (Digital Subscriber Line) transmits at fast speeds on existing standard copper telephone wiring.
Some DSL installations include a dial tone, providing users with both voice and data communications. These DSL installations often require that filters be installed to reduce noise interference when voice communications share the same line. ADSL is one of the more popular types of DSLs. As shown in Figure 9-25, ADSL (asymmetric digital subscriber line) is a type of DSL that supports faster transfer rates when receiving data (the downstream rate) than when sending data (the upstream rate). ADSL is ideal for Internet access because most users download more information from the Internet than they upload.
·         FTTP
FTTP, which stands for 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 and FTTB. FTTH (Fiber to the Home) provides home users with Internet access via fiber-optic cable. Similarly, FTTB (Fiber to the Building) refers to small businesses that use fiber-optic cables to access the Internet. With FTTP service, an optical terminal at your location receives the signals and transfers them to a router connected to your computer. As the cost of installing fiber decreases, more homes and businesses will opt for this high-speed Internet access.
·         T-Carrier Lines
A T-carrier line is any of several types of long-distance digital telephone lines that carry multiple signals over a single communications line. Where as a standard dial-up telephone line carries only one signal, digital T-carrier lines use multiplexing so that multiple signals share the line. T-carrier lines provide very fast data transfer rates. Only medium to large companies usually can afford the investment in T-carrier lines because these lines are so expensive.
·         ATM
ATM (Asynchronous Transfer Mode) is a service that carries voice, data, video, and multimedia at very high speeds. Telephone networks, the Internet, and other networks with large amounts of traffic use ATM. Some experts predict that ATM eventually will become the Internet standard for data transmission, replacing T3 lines.

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 power line cable network uses the same lines that bring electricity into the house. A phone line 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?

·         Twisted-Pair Cable
One of the more widely used transmission media for network cabling and telephone systems is twisted-pair cable. Twisted-pair cable consists of one or more twisted-pair wires bundled together. Each twisted-pair wire consists of two separate insulated copper wires that are twisted together. The wires are twisted together to reduce noise. Noise is an electrical disturbance that can degrade communications.
·         Coaxial Cable
Coaxial cable, often referred to as coax (pronounced KO-ax), consists of a single  copper wire surrounded by at least three layers: (1) an insulating material, (2) a woven or braided metal, and (3) a plastic outer coating (Figure 9-37). Cable television (CATV) network wiring often uses coaxial cable because it can be cabled over longer distances than twisted-pair cable. Most of today’s computer networks, however, do not use coaxial cable because other transmission media such as fiber-optic cable transmit signals at faster rates.
·         Fiber-Optic Cable
The core of a fiber-optic cable consists of dozens or hundreds of thin strands of glass or plastic that use light to transmit signals. Each strand, called an optical fiber, is as thin as a human hair. Inside the fiber-optic cable, an insulating glass cladding and a protective coating surround each optical fiber. Fiber-optic cables have the following advantages over cables that use wire, such as twisted-pair and coaxial cables:
• Capability of carrying significantly more signals than wire cables
• Faster data transmission
• Less susceptible to noise (interference) from other devices such as a copy machine
• Better security for signals during transmission because they are less susceptible to noise
• Smaller size (much thinner and lighter weight)
·         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 high speed 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.

Wednesday, December 11, 2013

Chapter 8

Name : Genesius Hartanto
NIM : 1701308971
Class : 01PCT
Professor : Mr. Tri Djoko Wahjono, Ir., M.Sc.

1.       What is system software, and what are the two types of system software?
System software (or systems software) is computer software designed to operate and control the computer hardware and to provide a platform for running application software.
The two types of system software :
a.       The operating system (prominent examples being z/OS, Microsoft Windows, Mac OS X and Linux), allows the parts of a computer to work together by performing tasks like transferring data between memory and disks or rendering output onto a display device. It also provides a platform to run high-level system software and application software
b.      Utility software helps to analyze, configure, optimize and maintain the computer

2.       What are the functions of an operating system?
a.       Booting the computer
b.      Performs basic computer tasks eg managing the various peripheral devices eg mouse, keyboard
c.       Provides a user interface, e.g. command line, graphical user interface (GUI)
d.      Handles system resources such as computer's memory and sharing of the central processing unit (CPU) time by various applications or peripheral devices
e.      Provides file management which refers to the way that the operating system manipulates, stores, retrieves and saves data

3.       What is the startup process on a personal computer?
In computing, booting (also known as booting up) is the initial set of operations that a computer system performs after electrical power to the CPU is switched on or when the computer is reset. The process begins when a computer is turned on for the first time, is re-energized after being turned off, when it is reset or when the operator invokes a LOAD function from the console, and ends when the computer is ready to perform its normal operations. On modern general purpose computers, this can take tens of seconds and typically involves performing a power-on self-test, locating and initializing peripheral devices, and then finding, loading and starting an operating system. Many computer systems also allow these operations to be initiated by a software command without cycling power, in what is known as a soft reboot, though some of the initial operations might be skipped on a soft reboot. A boot loader is a computer program that loads the main operating system or runtime environment for the computer after completion of the self-tests.
The computer term boot is short for bootstrap or bootstrap load and derives from the phrase to pull oneself up by one's bootstraps.The usage calls attention to the requirement that, if most software is loaded onto a computer by other software already running on the computer, some mechanism must exist to load initial software onto the computer. Early computers used a variety of ad-hoc methods to get a small program into memory to solve this problem. The invention of read-only memory (ROM) of various types solved this paradox by allowing computers to be shipped with a start up program that could not be erased. Growth in the capacity of ROM has allowed ever more elaborate start up procedures to be implemented.
On general purpose computers, the boot process begins with the execution of an initial program stored in boot ROMs or read in another fashion. In some older computers, the initial program might have been the application to run, if no operating system was used, or the operating system. In other computers, the initial program is a boot loader that may then load into random-access memory (RAM), from nonvolatile secondary storage (such as a hard disk drive) or, in some older computers, from a medium such as punched cards, punched tape, or magnetic tape, the binary code of an operating system or runtime environment and then execute it. If the boot loader is limited in its size and capabilities, it may, instead, load a larger and more capable secondary boot loader, which would then load the operating system or runtime environment. Some embedded systems do not require a noticeable boot sequence to begin functioning and when turned on may simply run operational programs that are stored in ROM.

4.       What are features of windows 7, Mac OS X, UNIX, and Linux Operating Systems?
a.       Windows 7
Windows 7 is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops, netbooks, tablet PCs, and media center PCs. It was released to manufacturing on July 22, 2009, and became generally available for retail worldwide on October 22, 2009, less than three years after the release of its predecessor, Windows Vista. Windows 7's server counterpart, Windows Server 2008 R2, was released at the same time. Windows 7 is succeeded by Windows 8.
Unlike Windows Vista's many new features, Windows 7 was an incremental upgrade designed to work with Vista-compatible applications and hardware. Presentations given by Microsoft in 2008 focused on multi-touch support, an updated Windows shell with a new taskbar, referred to internally as the Superbar, a home networking system called HomeGroup,  and performance improvements. Some standard applications that have been included with prior releases of Microsoft Windows, including Windows Calendar, Windows Mail, Windows Movie Maker, and Windows Photo Gallery, are not included in Windows 7; most are instead offered separately at no charge as part of the Windows Essentials suite.

b.      Mac OS X
Mac OS X is a multitasking operating system available only for Apple computers.

c.       UNIX
-          multi-user
more than one user can use the machine at a time
supported via terminals (serial or network connection)
-          multi-tasking
more than one program can be run at a time
-          hierarchical directory structure
to support the organisation and maintenance of files
-          portability
only the kernel ( <10%) written in assembler
tools for program development
a wide range of support tools (debuggers, compilers)

d.      Linux
Linux is an operating system, a software program that controls your computer. Most vendors load an operating system onto the hard drive of a PC before delivering the PC, so, unless the hard drive of your PC has failed, you may not understand the function of an operating system.
An operating system solves several problems arising from hardware variation. As you're aware, no two PC models (or models of other computers, for that matter) have identical hardware. For example, some PCs have an IDE hard drive, whereas others have a SCSI hard drive. Some PCs have one hard drive, others have two or more. Most PCs have a CD-ROM drive, but some do not. Some PCs have an Intel Pentium CPU, whereas others have an AMD K-6, and so on. Suppose that, in a world without operating systems, you're programming a new PC application, perhaps a new multimedia word processor. Your application must cope with all the possible variations of PC hardware. As a result, it becomes bulky and complex. Users don't like it because it consumes too much hard drive space, takes a long time to load, and - because of its size and complexity - has more bugs than it should.
Operating systems solve this problem by providing a single standard way for applications to access hardware devices. When an operating system exists, applications can be more compact, because they share the commonly used code for accessing the hardware. Applications can also be more reliable because this code is written only once, and by expert programmers, rather than by every application programmers.
As you'll soon learn, operating systems do many other things as well; for example, they generally provide a file system so that you can store and retrieve data, and a user interface so that you can control the operation of your computer. However, if you think of a computer's operating system as its subconscious mind, you won't be far off the mark. It's the computer's conscious mind - applications such as word processors and spreadsheets - that do useful work. But, without the subconscious - the operating system - the computer would cease breathing and applications would not function.

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-commeree applications. Novell’s NetWare is a server operating system designed for client/server networks.

6.       What are the features of several embedded operating systems?
An embedded system is a computer system with a dedicated function within a larger mechanical or electrical system, often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal computer (PC), is designed to be flexible and to meet a wide range of end-user needs. Embedded systems control many devices in common use today.
Modern embedded systems are often based on microcontrollers (i.e CPUs with integrated memory and/or peripheral interfaces)  but ordinary microprocessors (using external chips for memory and peripheral interface circuits) are also still common, especially in more complex systems. In either case, the processor(s) used may be types ranging from rather general purpose to very specialised in certain class of computations, or even custom designed for the application at hand. A common standard class of dedicated processors is the digital signal processor (DSP).
The key characteristic, however, is being dedicated to handle a particular task. Since the embedded system is dedicated to specific tasks, design engineers can optimize it to reduce the size and cost of the product and increase the reliability and performance. Some embedded systems are mass-produced, benefiting from economies of scale.
Physically, embedded systems range from portable devices such as digital watches and MP3 players, to large stationary installations like traffic lights, factory controllers, and largely complex systems like hybrid vehicles, MRI, and avionics. Complexity varies from low, with a single microcontroller chip, to very high with multiple units, peripherals and networks mounted inside a large chassis or enclosure

7.       What is the purpose of several utility programs?

Utility Software is essentially what takes care of your computer system. Utility Software consists of but is not limited to the following: Disk cleaner - Finds files that are not in use anymore, or may have never been in use that take up a lot of space on the hard drive. Defragmenter - Locating the files that may be broken and therefore not completely functionary to the system and grouping them together, placing them in a different area of your computer’s hard drive. Checker - Similar to cleaners, disk checkers scan your computer to see if you have any files that are corrupt or unusable due to incorrect saving, to create a more capable computer system. Anti-virus system - A utility that scans your computer for threats or viruses that have made their way on to your computer, whether it’s from visiting un-trusted websites or downloads. It quarantines any viruses and allows you to delete them how you wish. Space analyzer - This option shows you how much of your hard drive is being used and by what. It gives you the size of each document, folder, and systems and groups it all together to also show you how much space is not being used. Backups " Backing up a system is handy to do and very recommended for important files. It saves or copies on your computer system and can restore all or portions of a document or system in the case of a system error, or improper saving of a document. Networks - This utility will check your computer's connectivity to one or more networks. It offers ways of repairing lost connections as well as keeps a record of networks you may have used. All of these put together are used to optimize your computer and make it work in the most efficient way possible.

Chapter 7

Name : Genesius Hartanto
NIM : 1701308971
Class : 01PCT
Professor : Mr. Tri Djoko Wahjono, Ir., M.Sc.

1.       How Are Storage Devices Different from Storage Media?
·         Storage device refers to the apparatus for recording computer data. Examples are the RAM, floppy drives, ZIP drives, and other disks drives. While, storage media are the materials on which data are written and stored or a devices that store application and user information. Examples are the floppy disks, optical discs, hard disks, etc.
·         A storage device is the computer hardware that records and/or retrieves items to and from storage media.

2.       What Are the Characteristics of an Internal Hard Disk?
A hard disk drive (HDD) is a data storage device used for storing and retrieving digital information using rapidly rotating disks (platters) coated with magnetic material. An HDD retains its data even when powered off. Data is read in a random-access manner, meaning individual blocks of data can be stored or retrieved in any order rather than sequentially. An HDD consists of one or more rigid ("hard") rapidly rotating disks (platters) with magnetic heads arranged on a moving actuator arm to read and write data to the surfaces.

The primary characteristics of an HDD are its capacity and performance
·         The capacity of a hard disk
Is determined from whether it uses longitudinal or perpendicular recording, the number of platters it contains, and the composition of the magnetic coating on the platters.
·         Performance
A.      Time to access data
The factors that limit the time to access the data on an HDD are mostly related to the mechanical nature of the rotating disks and moving heads. Seek time is a measure of how long it takes the head assembly to travel to the track of the disk that contains data. Rotational latency is incurred because the desired disk sector may not be directly under the head when data transfer is requested. These two delays are on the order of milliseconds each. The bit rate or data transfer rate (once the head is in the right position) creates delay which is a function of the number of blocks transferred; typically relatively small, but can be quite long with the transfer of large contiguous files. Delay may also occur if the drive disks are stopped to save energy.
Time to access data can be improved by increasing rotational speed (thus reducing latency) and/or by reducing the time spent seeking. Increasing areal density increases throughput by increasing data rate and by increasing the amount of data under a set of heads, thereby potentially reducing seek activity for a given amount of data.

B.      Seek time
Seek time has continued to improve slowly over time. Some desktop and laptop computer systems allow the user to make a tradeoff between seek performance and drive noise. Faster seek rates typically require more energy usage to quickly move the heads across the platter, causing louder noises from the pivot bearing and greater device vibrations as the heads are rapidly accelerated during the start of the seek motion and decelerated at the end of the seek motion. Quiet operation reduces movement speed and acceleration rates, but at a cost of reduced seek performance.
C.      Latency
Latency is the delay for the rotation of the disk to bring the required disk sector under the read-write mechanism. It depends on rotational speed of a disk, measured in revolutions per minute (rpm). Average rotational latency is shown in the table below, based on the statistical relation that the average latency in milliseconds for such a drive is one-half the rotational period.
D.      Data Transfer rate
HDD data transfer rate depends upon the rotational speed of the platters and the data recording density. Because heat and vibration limit rotational speed, advancing density becomes the main method to improve sequential transfer rates. Higher speeds require more power absorbed by the electric engine, which hence warms up more. While areal density advances by increasing both the number of tracks across the disk and the number of sectors per track, only the latter increases the data transfer rate for a given rpm. Since data transfer rate performance only tracks one of the two components of areal density, its performance improves at a lower rate.

3.       What Is the Purpose of Network Attached Storage Devices, External and Removable Hard Disks, and Hard Disk Controllers?
·         Network Attached Storage Device
NAS is useful for more than just general centralized storage provided to client computers in environments with large amounts of data. NAS can enable simpler and lower cost systems such as load-balancing and fault-tolerant email and web server systems by providing storage services.
File-level computer data storage connected to a computer network providing data access to a heterogeneous group of clients. NAS not only operates as a file server, but is specialized for this task either by its hardware, software, or configuration of those elements.
·         External and Removable Hard Disks
An external hard disk is a separate freestanding hard disk that connects with a cable to a USB or FireWire port on the system unit or communicates wirelessly. External hard disks have storage capacities up to 4 TB and more.
A removable hard disk can be inserted or removed from a built-in or external drive. Removable hard disks have storage capacities up to 1 TB
·         Hard Disk Controller
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 in a computer. A hard disk controller may be part of the hard disk on the motherboard, or it may be a separate
4.       What Are the Various Types of Flash Memory Storage? 
·         A solid state drive (SSD)
Typically uses flash memory to store data, instructions, and information. Data storage device using integrated circuit assemblies as memory to store data persistently. SSD technology uses electronic interfaces compatible with traditional block input/output (I/O) hard disk drives, thus permitting simple replacement in common applications.
·         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 or writer. Common memory cards include CompactFlash, Secure Digital (SD), Secure Digital High Capacity (SDHC), micro SD, microSDHC, xD Picture Card, Memory Stick, and Memory Stick Micro (M2).
·         A USB flash drive
Sometimes called a thumb drive, is a flash memory storage device that plugs in a port on a computer or mobile device.
·         An Express Card module
Is a removable device that it’s in an Express Card slots. Express Card modules can add memory, storage, communications, or other capabilities to a computer.

5.       What Is Cloud Storage, and What Are Its Advantages?
Cloud storage is a model of networked enterprise storage where data is stored in virtualized pools of storage which are generally hosted by third parties. Hosting companies operate large data centers, and people who require their data to be hosted buy or lease storage capacity from them or Internet service that provides storage for computer users.

Advantage of Cloud storages:
·         Companies need only pay for the storage they actually use, typically an average of consumption during a month. This does not mean that cloud storage is less expensive, only that it incurs operating expenses rather than capital expenses.
·         Organizations can choose between off-premise and on-premise cloud storage options, or a mixture of the two options, depending on relevant decision criteria that is complementary to initial direct cost savings potential; for instance, continuity of operations (COOP), disaster recovery (DR), security (PII, HIPPA, SARBOX, IA/CND), and records retention laws, regulations, and policies.
·         Storage availability and data protection is intrinsic to object storage architecture, so depending on the application, the additional technology, need effort and cost to add availability and protection can be eliminated.
·         Storage maintenance tasks, such as purchasing additional storage capacity, are offloaded to the responsibility of a service provider.
·         Cloud storage provides users with immediate access to a broad range of resources and applications hosted in the infrastructure of another organization via a web service interface.
·         Cloud storage can be used for copying virtual machine images from the cloud to on-premise locations or to import a virtual machine image from an on-premise location to the cloud image library. In addition, cloud storage can be used to move virtual machine images between user accounts or between data centers.
·         Many Cloud Storage providers offer free accounts which can be expanded through various techniques, which many people have started to take advantage of to get hundreds of gigabytes of free online storage.

6.       What Are the Characteristics of Optical Discs?
Is a flat, usually circular disc which encodes binary data (bits) in the form of pits (binary value of 0 or off, due to lack of reflection when read) and lands (binary value of 1 or on, due to a reflection when read) on a special material (often aluminum) on one of its flat surfaces. The encoding material sits atop a thicker substrate (usually polycarbonate) which makes up the bulk of the disc and forms a dust defocusing layer. The encoding pattern follows a continuous, spiral path covering the entire disc surface and extending from the innermost track to the outermost track. The data is stored on the disc with a laser or stamping machine, and can be accessed when the data path is illuminated with a laser diode in an optical disc drive which spins the disc at speeds of about 200 to 4,000 RPM or more, depending on the drive type, disc format, and the distance of the read head from the center of the disc (inner tracks are read at a higher disc speed). The pits or bumps distort the reflected laser light, hence most optical discs (except the black discs of the original PlayStation video game console) characteristically have an iridescent appearance created by the grooves of the reflective layer. The reverse side of an optical disc usually has a printed label, sometimes made of paper but often printed or stamped onto the disc itself. This side of the disc contains the actual data and is typically coated with a transparent material, usually lacquer. Unlike the 3½-inch floppy disk, most optical discs do not have an integrated protective casing and are therefore susceptible to data transfer problems due to scratches, fingerprints, and other environmental problems. Optical discs, which primarily store software, data, digital photos, movies, and music, contain microscopic pits (indentations) and lands (flat areas) in their middle layer. Optical discs commonly store items in a single track that spirals from the center of the disc to its edge. Like a hard disk, the ingle track is divided into evenly sized sectors.

7.       How Are the Various Types of Optical Discs Different?
There are numerous formats of optical direct to disk recording devices on the market, all of which are based on using a laser to change the reflectivity of the digital recording medium in order to duplicate the effects of the pits and lands created when a commercial optical disc is pressed. A CD-ROM, or compact disc read-only memory, is a type of optical disc that uses laser technology to store items Users can read the contents of standard CD-ROMs but cannot erase or modify their contents. Formats such as CD-R and DVD-R are "Write once read many" is a multisession disc on which users can record their own items, such as text, graphics, and audio, while CD-RW and DVD-RW are rewritable, more like a magnetic recording hard disk drive (HDD).

8.       How Are Tape, Magnetic Stripe Cards, Smart Cards, Microfilm and Microfiche, and Enterprise Storage Used?
·         Tape
A tape drive is a data storage device that reads and writes data on a magnetic tape. Magnetic tape data storage is typically used for offline, archival data storage. Tape media generally has a favorable unit cost and long archival stability.
·         A Magnetic Stripe Card
Is a type of card capable of storing data by modifying the magnetism of tiny iron-based magnetic particles on a band of magnetic material on the card. The magnetic stripe, sometimes called swipe card or magstripe, is read by swiping past a magnetic reading head. Such as credit card, entertainment card, bank card, or other similar card with a stripe that contains information identifying you and the card. A magnetic stripe card reader reads the information stored on the stripe.

·         A Smart Card
Any pocket-sized card with embedded integrated circuits.
Smart cards are made of plastic, generally polyvinyl chloride, but sometimes polyethylene terephthalate based polyesters, acrylonitrile butadiene styrene or polycarbonate. Since April 2009, a Japanese company has manufactured reusable financial smart cards made from paper. Smart cards can provide identification, authentication, data storage and application processing. Smart cards may provide strong security authentication for single sign-on (SSO) within large organizations.

·         Microfilm and microfiche
Microfilm is essentially 35mm photographic film that was used to take images of the pages of a book, a periodical volume or a newspaper.  The reel of film is then duplicated and sold to libraries.  Microfiche are flat sheets of photographic film about 4×6 inches in size. Reduce the amount of paper must handle, are inexpensive, and have the longest life of any storage media. Enterprises use computers, servers, and networks to manage and store huge volumes of data and information.
·         Enterprise Storage
Is the computer data storage designed for large-scale, high-technology environments of the modern enterprises. When comparing to the consumer storage, it has higher scalability, higher reliability, better fault tolerance, and much higher initial price. Some storage systems can provide more than 185 TB of storage, and optical disc servers hold hundreds of optical discs.
From the salesperson's point of view, the four main enterprise storage markets are:
·         Online storage - large disk array solutions, minimizing access time to the data, and maximizing reliability;
·         Backup - off-line storage for data protection, with a smaller price per byte than online storage, but at a cost of higher average access time; often uses sequential access storage, such as tape libraries;
·         Archiving - technically similar to backup, but its purpose is long-term retention, management, and discovery of fixed-content data to meet regulatory compliance, litigation protection, and storage cost optimization objectives;
·         Disaster recovery solutions, used to protect the data from localized disasters, usually being a vital part of broader business continuity plan.