It is possible that the data of a particular system may be spread in different branches of a company, but it must be controlled from one central location. Logically Organised: The database must be organised in a logical manner. For example. Shared: In a multi-user application, the database is designed such that the data can be shared or accessed by different users.
The sharing of data is possible, only if the database is integrated. Data independence: The most important objective of a database is the provision of data independence.
Most of the present day applications are generally data-dependent. If the storage structure of the data files is to be changed, the programme should also be modified accordingly. Instead, they form their requests in database query language. Among these applications are computer aided design systems, knowledge base and modeling systems. Database Programmes: the set of instructions given to the database system to perform the arithmetic and logical operations on data are also the important components of a DBMS.
These sets of instructions are called programmes. These instructions are given to interact among the different elements of the database. These instructions generally comprise a set of rules and relationships. It is required to meet the objectives of the database which we discussed in the previous section. Despite these disadvantages, today, a DBMS has become an essential system of data Management for all organisations.
A field is the lowest level logical unit in the data hierarchy. For example, a single character, viz; A has little meaning out of context. But when characters are combined to form a name e. The term file is also used to refer to a named area on a secondary storage device that contains a programme, textual material or even an image. All the records about authors for the publisher comprise a file. For example, if records are kept in a traditional file environment and an author moves, his or her address must be changed in all files that maintain the address data.
In a database, data about addresses of authors are stored only once and are made available to all departments. Therefore, only one update is needed.
The phrase data element, or elementary item, is also sometimes used. Although the data item may be treated as a molecule of the database, data items are grouped together to form aggregates described by various names.
For example, the data recurred is used to refer to a group of data items and a programme usually reads or writes the whole records. The data items could occasionally be further broken down into what may be called an automatic level for processing purpose. The first 2 digits of these number reflect the year of admission, the next 2 digits refer to the Regional Centre where the student has first opted for admission, the next 4 digits are simple sequence numbers and the last digits are check digits.
For the purpose of processing, it may sometimes be necessary to split the data item. All such items about which relevant information is stored in the database are called Entities.
The qualities of the entity which we store as information are known as attributes. An attribute may be expressed as a number or as a text. It may even be a scanned picture, a sound sequence, a moving picture, which is now possible in some visual and multi-media database. The principal components of a DBMS are a data description module and a data manipulation module. The data description module of the DBMS analyses the data requirements of applications programmes and transfers control to the data manipulation module, which retrieves the data from the database.
Most people are able to use a database management Notes without knowing its underlying structure. This ease, of course, is made possible by the four components of DBMS software: data definition language, data manipulation language, query language and report generator. Data Definition Language Database management systems provide a facility, known as the data definition language DDL , which can be used to define the conceptual schema and also give some details about how to implement this schema in physical devices used to store the data.
This definition includes all the entity sets and their associated attributes, as well as the relationships among the entity sets. The definition also includes any constraints that have to be considered, including the constraints on the value that can be assigned to given attribute and the constraints on the values assigned to different attributes in the same, or different, records. Data Manipulation Language DHL This is a language that enables users to access or manipulate as organised appropriate data model.
Data manipulation involves retrieval of data from the database, insertion of new data into the database and deletion or modification of existing data.
The first of these data manipulation operations is called a query. Query Language This language enables users to ask specific questions to the database. A marketing vice president trying to decide which items to sell at a discount, for example, might ask a database programme to list all inventory items with a profit margin greater than 30 percent.
The most popular query language is structured Query language SQL. Report Generator The report generator helps the user to design and generate reports and graphs in printed form. Report headings, column headings, page numbers and totals are just some of the features that are easy to include with the report generator. File Organisation: Based on the differences in the speed and method of access, there are three major methods of storing files of data in secondary storage: 1.
Sequential file organisation, in which records are organised in a particular order. Direct file organisation, in which records are not organized in any particuler order. Indexed Organisation, in which records are organised sequentially, but indexes built into the file allow a record to be accessed, either directly or sequentially. Sequential file processing means records are in order according to a primary key field. If a particular record in a sequential file is wanted, all the prior records in the file must be read before reaching the desired records.
Tape storage is limited to sequential file organisation. Operationally, the magnetic tape is same as the one in home and automobile tape decks. If the key field in an employee record is employee name, the records are ordered and processed alphabetically by last name.
A sequential file is processed from start to finish. The entire file must be processed, even if only one record is to be updated. Sequential Access File Direct File Organisation Direct access, allows the computer to go directly to the desired record by using a primary key. The computer does not have to read all preceding records in the file as it does if the records are arranged sequentially. Direct access requires disk storage.
In fact, a disk device is called a direct-access storage device DSAD because the computer can go directly to the desired record on the disk. An added advantage of direct access organisation is the ability to read and return a record to its same place on the disk. This is called updating in place. Direct Access File Indexed File Organisation It is useful in applications where a file needs to be in sequential order but, in addition, access to individual records is needed. In indexed file organisation, records are stored in the file in sequential order, but the file also contains an index.
The index is like a directory, with the keys to all records listed in order ascending or descending. To access a record directly, the record key primary key must be located in the index. The address associated with the key is then used to locate the record on the disk. To access the entire file of records sequentially, begin with the first record and proceed through the rest of records.
Although the hierarchical structure is a natural way to model truly, it has certain drawbacks. The symmetry is generally missing in a hierarchical approach and anomalies arise in retrieval of records, due to the complicated programming concepts used in an hierarchical database.
Codd, in In the relational data structure, data is viewed as organised in table as shown in the table on page As per the systems design, there can be many Tables in a database. A two dimensional Table is the most natural way to represent data for a general user. Each Table closely resembles a conventional sequential file with rows representing records of the data, and columns representing field of the records.
Actually, each Table is a special case of construct known as a relation. A database constructed using relations is referred to as a relational database. The relational approach is based on the mathematical theory of relation and therefore, the results of relational mathematics can be directly applied to such a database.
Thus, a given entity can have any number of superiors, as well as any number of subordinates. There can be many-to-many relationships among entities Complex network besides one-to- many simple Network.
The relationships between entities are generally represented by using pointers, called the Link Nodes. The complex network is better than the simple network because the former can be broken into many simple networks, but it is difficult to convert data representation from simple to complex network. The general form of network structure is shown below: Network Structure 1.
If more computing power is needed, one way to get it is to buy a larger computer system. But buying a larger computer system is not possible for many small businesses or companies. Another problem arises for those who are geographically dispersed. They may need to send messages to, receive messages from, or share problems at many different locations.
One solution to this problem is to keep separate data files at each location. But this approach is very costly and potentially a dangerous solution. The solution to both issues, the need Notes for more power and the ability to receive messages and share data are found in data communication technology.
Even for a simple important exercise of printing any information from a computer by an attached printer to a computer, there is a requirement for error free data transmission from the computer to the printer.
The whole concept of data communication is based upon principles of sending data, checking and confirming its receipt and following error correction technique, to ensure accurate data transmission. Communication Process 1.
They were never planned to send Data. So to send data through telephone lines, you have to convert the data into the format which can be read by telephone lines.
These are called analog signals. For data communication between computers to take place over a telephone line, the digital pulses of the data to be transmitted must be converted to an analog signal before these are transmitted.
After its journey over the telephone lines, the analog signal must be re-converted to digital pulses so that it can be used by the receiving computer. The process of converting digital pulses to an analog signal is called modulation. And the process of re-converting an analog signal to digital pulses is called demodulation. The device that accomplishes modulation-demodulation process is called a modem.
A device using the simplex mode of transmission can either send or receive data, but it cannot do both. Simplex mode circuit is seldom used because a return path is generally needed to send acknowledgement, control or error signals.
Full-duplex Mode: This mode allows a device to receive and send data simultaneously. A full duplex mode is faster since it avoids the delay that occurs in a half-duplex circuit each time the direction of transmission is changed.
An example is a citizens band radio, where the user must either talk or listen, but cannot do both at the same time. Transmission Modes 1. Twisted pair Cable This type of cable is made of pairs of thin strands of insulated wire twisted together. Twisted pair is the least expensive type of networking cable and has been in use the longest. In fact, it is the same type of cabling used inside most homes for telephone communications. Twisted pair cabling can be used with both analog and digital data and is commonly used for LANs.
Twisted pair cable is rated by category, which indicates the type of data, speed, distance and other factors that the cable supports. Category 3 twisted pair cabling is a regular telephone cable with higher speed and quality cabling. For instance, Category 5 and Category 6 are Frequently used for home or business networks.
The pairs of wires in twisted pair wires are twisted together to reduce interference and improve performance. To further improve performance, it can be shielded with a metal lining. Twisted pair Cable Coaxial Cable This medium also known as coax , pioneered by the cable television industry, was originally developed to carry a large number of high speed video transmissions. A coaxial cable consists of a relatively thick centre wire surrounded by insulation and then a shield of braided wire the shield blocks electromagnetic signals from entering the cable.
Coaxial cable are available in both baseband and broadband versions. Both type of coaxial cabless are used today in Notes computer networks. Coax is also used for short run telephone transmissions outside the home and for cable television delivery. Although more expensive than twisted pair cabling, it is much less susceptible to interference and can carry more data more quickly. Coaxial Cable Fiber Optic Cable This is the newest and fastest of the three types of wired transmission media.
It uses clear glass or plastic fibre strands, each about the thickness of a human hair, to transfer digital data represented by light pulses. The light pulses are sent through the cable by a laser device at speeds of billions of bits per second. Each strand has the capacity to carry data for several television stations, or thousands of voice conversations. Fiber Optic connectors are less standardised than connectors for other types of wired media, so it is important to use cables with the connectors that match the hardware with which the cable will be used.
Fiber Optic cable is commonly used for the high speed backbone lines of a network, such as to connect networks housed in separate buildings or for the Internet infrastructure. It is used for telephone backbone lines and is increasingly being installed by telephone companies all the way to the home or business to provide super-fast connections directly to the end user.
The biggest advantage of fiber optic cabling is speed. The main disadvantage of fiber optic cabling is the initial expense of both the cable and the installation. Fiber Optic Cable b Wireless Network The most common types of wireless transmission media used in computer and communications networks are microwave, satellite and infrared. Sometimes, Notes a single piece of hardware functions as both the receiver and transmitter; if so, it is commonly called a transmitter or transceiver.
Microwave and Satellite Transmission Microwaves are high frequency radio signals. Microwave signals can be sent or received using microwave stations or satellites.
Both methods can send large quantities of data speeds over long distances. Microwave stations sometimes referred to as terrestrial microwave stations are earth-based stations that can transmit microwave signals directly to each other over distances of up to about 30 miles. Microwave signals sent via microwave station transmission are line of sight, which means that the microwaves must travel in a straight line from one station to another without encountering any obstacles.
To avoid building mountains and the curvature of the earth obstructing the signals, microwave stations are usually placed on tall buildings, towers and mountain tops. Microwave stations typically contain both a dish shaped microwave antenna and a transceiver. When one station receives a transmission from another, it amplifies it and passes it to the next station.
Microwave stations can also exchange data transmissions with satellites, discussed next. Microwave stations designed specifically to communication with satellites, such as for satellite TV and satellite Internet services are typically called satellite dishes. Satellite dishes are usually installed permanently where they are needed, but they can also be mounted on trucks, boats and other types of transportation devices when portable transmission capabilities are necessary or desirable, such as on military or recreation vehicles.
Communications satellites are space-based devices launched into orbit around the earth to receive and transmit microwave signals to and from earth. Originally used primarily to facilitate microwave transmission when transmission stations were not economically viable such as over large, sparsely populated areas or were physically impractical such as over large bodies of water , satellites can now send and receive transmissions to and from a variety of other devices, such as personal satellite dishes used for satellite television and Internet services, GPS receivers, satellite radio receivers and satellite phones.
Satellites Communications 1. This communication channel configuration can be inefficient and costly, if a terminal is not active enough to keep the line busy. Multi Point In this configuration, three or more devices, e.
Compared to point-to-point configuration, multipoint channel configuration is more efficient and less costly, because it reduces the amount of inter-cabling needed. These devices may be computers, telephones or other communicating devices. In case of computer, it is the connection between two or more autonomous computers. These computers are connected with each other for information interchange. For connecting two computers are available different media like copper wires, microwaves, optical fibers and satellite.
So, a network can spread over an area which could be as small as a room, or as wide as the entire world. Depending on the span of the computer network, any network can be placed in either of the following three categories: 1.
LAN 2. WAN 3. MAN Local Area Network A local area network LAN is two or more computers directly within a small well defined area such as a room, building or group of closely placed buildings.
Some computers require that all the computers be of a certain brand, while others allow a variety of brands to be connected. Most LANs allow cables of about 1, feet, but some allow cables of several miles to be used. This type of network is usually limited to use by large corporations and government agencies because of the high cost involved in installing and maintaining these.
A WAN is a network that links separate geographical locations and this network can be a public system or any of the various packet switched services provided by the public telecommunication agencies. The main difference between a LAN and WAN is that former is under the complete control of the owner, whereas the latter needs the involvement of another authority like the telecom department.
Increasingly, wireless MANs are being created by cities or large organisations including Microsoft and Google to provide free, or low cost, Internet access to area residents.
Four of the most common physical topologies are: star, bus, ring and mesh. Star Networks With a star network — one of the most common network topology - there is a device to which all the computers and other devices in the network connect, forming a star shape. The central device contains multiple ports that are used to connect the various nodes on the network such as computers and printers and all network transmissions are sent through the central device.
If an individual computer or other node on the network fails, the other nodes and the network itself are not affected. If the central device fails, however, the network can not function, although the individual nodes on the network can still work independently. Star networks are common in traditional mainframe environments, as well as in small office, home and wireless networks.
Star topology Bus Networks A bus network has no central hub. Instead, it consists of a central cable to which all network nodes are attached. In a bus network, all data is transmitted down the bus line from one node to another and only oneline can transmit at a time. Similarly, in a star network, if an individual computer or other node on the network fails, the other nodes and the network itself are not affected. It is only if the bus line fails that the network itself would not function. Like a bus networks, this network does not have a central hub but the computers and other network devices are connected in a ring formation from one node to the next, without the use of a central cable.
In a ring network, data typically travels from one node to another around the ring in one direction only. Date Published: September Revised content from the original publication can now be found in the following publications:. As more organizations share information electronically, a common understanding of what is needed and expected in securing information technology IT resources is required. This document provides a baseline that organizations can use to establish and review their IT security programs.
The document gives a foundation that organizations can reference when conducting multi-organizational business as well as internal business. Jayant Baliga Solution Manual. Futrell 12 Test Bank. Ebbing and Steven D. Gammon 9 Solution Manual. Freeman 9. Freeman 9 Test Bank. Schultz Instructor Resource Manual.
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McCann 2 Test Bank. Bagley Instructor's Manual. Bagley Test Bank. Trevino 5 Instructor's Manual. Trevino 5. Students must complete all credits that satisfy requirements for the BS and MS programs, with a minimum of 3 credits maximum 9 credits overlapping from the following courses:. Students in the Information Technology, BS program may apply to this option if they have earned 60 undergraduate credits and take graduate level courses after completion with an overall GPA of 75 credit s with an overall GPA of at least 3.
Criteria for admission are identical to criteria for admission to the Applied Information Technology, MS program. Students must complete all credits that satisfy requirements for the BS and MS programs, with a minimum of 3 credits maximum 12 credits overlapping from the following courses :. Students also have the option to take up to 6 additional credits of graduate coursework on reserve , which can be used for the MS degree only. See AP. Catalog Navigation Contact Information.
Find Your Advisor. The objectives include: Be employed in a position in which they have successfully used their information technology skills as evidenced by achieving improved organizational objectives Progress through increasing levels of responsibility in the workplace Demonstrate ethical, social and professional responsibility consistent with organizational values Work effectively in teams, whether as a participant or as a leader Grow through self-study, continuing education and professional development relevant to their profession The program can be successfully completed in eight full-time semesters with an average of 15 credits each semester.
Admissions Students who meet Mason's general eligibility requirements may apply for admission to the IT major. Policies For policies governing all undergraduate degrees, see AP.
Grades Students must have a C or better in any course that satisfies a prerequisite for an IT course. Course Repeat Policy In addition to the University's Undergraduate Course Repeat Policy, the following courses listed have additional repeat restrictions: A student who has taken IT twice may not take IT for their third attempt, nor will they be permitted to start over with three attempts of IT in lieu of taking IT A student who has taken IT twice may not take IT for their third attempt, nor will they be permitted to start over with three attempts of IT in lieu of taking IT Termination from the Major No math, science, or Volgenau School of Engineering course that is required for the major may be attempted more than three times.
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