With plasma televisions quickly becoming the standard television of the day the prices are constantly coming down and the demand for plasma is going up.

Advantages of plasma TV:

Plasma TVs are widely popular, due to the advantages they offer. In this article, we’ll go over a few of the pros and cons of Plasma screens, as well as tips for buying a plasma TV.

• Plasma screens are very shallow. Usually the screen will take up about 2 inches, and the entire TV or finished screen will be just a few inches deep. This means that your TV takes up very little room, and is easily mounted on a wall.
• Plasma screens also have an excellent contrast, and can display nearly perfectly dark black. Plasma screens can also display very bright colors. This makes them ideal for watching movies.
• Plasma screens can also come in extra large sizes. The largest plasma screen in the world is 103 inches across. You can easily buy plasma screens up to about 65 inches.

Disadvantages of plasma TV:

Even though they have some significant advantages they do have some remarkable disadvantages on the other hand.

• Plasma screens begin losing their brightness after about 2,000 hours of use. The latest model plasma screens will be half as bright as they originally were after about 60,000 hours of use.
• Plasma screens are very fragile, so they are hard to install and ship. Of course, they are also at an increased risk of breaking.
• Above about 6,000 elevations, Plasma screens will emit a humming noise. Very few people will have an issue with this, though, as very few people live above 6,000 feet elevation.

OSI reference Model layers

There are 7 layers in OSI reference model, starting from the bottom Physical Layer, Data Link layer, Network Layer, Transport Layer, Session Layer, Presentation layer and Application layer. These are the following layers in OSI reference model, each layer does not define one protocol osi defines any number of protocol therefore each layer consists of multiple protocols each provides a unique service in aligning with the function of that layer.

Role of OSI in data communications model

Basically OSI has 7 layers clearly states the functions of data communication protocols very accurately and clearly.  Whenever the data is transferred between co-operating applications across a Intervening network each layer of OSI represents a function and identifies each by its name and provides a short snippet of information for it.

What are Addressing, Routing and Multiplexing?

To transfer the data from two different hosts, you need to shift the data across the network to the exact host and from there you need to navigate to the exact user or process. This can be achieved by Addressing, Routing and Multiplexing.

Addressing

These are IP addresses, which help to identify each and every host across the network. Helping the data to reach the correct host.

Routing

It is a process of moving the data packets from source to the end point.

Multiplexing.

Multiplexing plays an important role in delivering data to the correct source, or module within the host. These three functions are addressing between hosts, routing between networks, and multiplexing.

Protocol and port numbers deliver data to the correct software module within the host.

Each of these functions – addressing between hosts, routing between networks, and multiplexing.

When realized in a computer program, the ADT is represented by an interface, which shields a corresponding implementation. Users of an ADT are concerned with the interface, but not the implementation, as the implementation can change in the future.

Construct abstract data types

The term abstract data type is about as dry and technical sounding as you can get. Yet the concept of an abstract data type, is something we should apply in every single one of our application efforts, sometimes without even realizing that we are doing it. An abstract data type is a collection of information and operations that act on that information. An ADT can represent computer objects such as lists, records, stacks, arrays, and tables; but an ADT can also represent real world objects, such as a company, a product or the set of assembly line operation at a factory.

PL/SQL offers several different constructs with which to build and manage ADTs, most importantly the package. The most general description of an ADT, in fact, sounds just like the description of a package: a collection of data and operations on that data.

Build an ADT in phases

There are four phases to build ADT, they are

• Clarify the data to be represented by the ADT. Make sure you understand all the attributes of the data and the way it is used in your application.
• List the key features and functions of the ADT as it relates to the underlying data. Don’t write any code until you have come up with a comprehensive list of all the operations on and by the ADT.
• Build the interface for the ADT. This is equivalent to designing the specification of all the modules, which are called by programmers to manipulate the ADT. Translate the list of features into procedure and function calls.
• Build the body of code behind the interface. You know how programmers will manage the ADT, since they must work with the specification. The final phase is to actually implement the ADT.

Client side testing

Testing the new query

When you are testing a new query you should test the query by running it. If all goes well, the new query will run rather quickly and you should inspect all the record in the table of results.

Server side testing

On part of SQL server testing, it is totally different when compared to other types of testing, we can have following as major portions of SQL server testing.

Code compliance testing

In code compliance testing, the code will be checked in compliance with requirements, developer can develop the code in different ways for a requirement. When a piece of code arrives to tester, he has to look into the following areas in SQL server code compliance testing

• Parameter passage: These plays very important with data type and length, parameter movement.
• Code blocking: Faster code will leave the begin and end for single statement, when code is changed or modified and a code will execute even though condition fails, as a tester you should make sure that which code is in block and out of block.
• Condition/Loops: In this simple condition is easy to understand and long condition will put confuse to a developer. The meaning of loop will change with dowhile and while. As a tester you need to make sure that they are properly conditioned. We can put this under branch testing.
• Exception handling: This is very important area, which comes under range testing, every report has to be sent back to the caller, and either it is requested result or not.
• Code commenting/alignment: This is low priority task compared to others but plays very important role in future versions and maintenance of the code.
• Return values: For some of the code, returns values are mandatory and the return values should be in contest of requirement.

Performance testing

This is validating database administrator role, performance of piece of code plays major role in network based project, after code is in-compliance with the requirement.

• SQL Queries: This is the closure area where you will be looking for optimization of code; queries are source of interacting data on SQL server, SQL queries can be written in different forms and some of the queries will be differentiated only with execution plan to identify the optimized one.
• Indexing: This is area where performance could be increased for the requested queries
• Bulk transaction: When there is bulk data transaction we must sure that certain objects are disabled.
• Clustering: SQL server clustering can provide fault tolerance for many aspect of a SQL server, such as hardware, network, operating system and application failure, make sure that it will not affect the performance and database is clustered on required portions.
• Database designing: This is the basic area to look for optimization; too much normalization will affect the performance.
• Data types: the lazy designers always use the maximum data type’s usage. In data types valid or invalid and use varchar (8), these data type will consume more memory, which is not used by the code but still occupying, which will intern increasing the paging.
• Locking/Unlocking: Some of the code will lock certain portions and until it is released other operations are not performed.

Integration testing

In order to get certain portions of data, we may require integration of different server and following are major areas to look on aspect of integration

• Calling of external stored procedure
• Usage of multiple servers

Protocol

Communication between computer in network or a different network requires certain set of rules called protocols.

Socket

Socket can be understood as a place used to plug in just like electric sockets.

Client/Server

A computer, which requests for some service from another computer is called client. The one that processes the request is called as server.

Internet address

Every computer connected to a network has a unique IP address. An IP address is a 32 bit number which has four number separated by periods. It is possible to connect to the Internet either directly or by using Internet service provider.

Domain naming service

It is very difficult to remember a set of number to connect to the Internet. The domain naming service is used to overcome this problem. It maps one particular IP address to a string of characters.

Inet address

There are classes provided in java to enable networking. They are found in the java.net package. InetAddress is one such class, which is used to encapsulate the IP address and the DSN. To create an instance of InetAddress class factory method are used, as there are no visible constructors available for this class. Factory methods are conventions where static methods return an instance of that class.

Datagram

Datagram is type of packet that represents an entire communication. There is no necessity to have connection or disconnection stages when communicating using Datagram. There are two classes in java, which enables communication-using Datagram.

• Datagram packet is the class, which acts as the data container
• Datagram socket is a mechanism used to send or receive Datagram packets.

TCP/IP

TCP/IP sockets are the most reliable, bi-directional, stream protocols. It is possible to send arbitrary amount of data using TCP/IP. Sockets are used for data communication using this protocol. There are two kinds of sockets in java – a server and client.

• A socket class object establishes connection between the client and the server.
• The server socket class object waits for the client to make a connection.

• Linear network
• Ring network
• Mesh network

Linear network

Linear network are two types they are

Point-to-point network

A point-to-point network is normally made of an STS multiplexer, an STS demultiplexer, and zero or more regenerators with no add/drop multiplexers, the signal flow can be unidirectional or bi-directional.

Multipoint network

A multipoint network uses ADMs to allow the communications between several terminals. An ADM removes the signal belonging to the terminal connected to it and adds the signal transmitted from another terminal. Each terminal can send data to one or more downstream terminals.

Automatic protection switching

To create protection against failure in linear network, SONET defines automatic protection switching. This APS has three schemes are common for protection in linear channels protocol.

• One-plus-one APS: In this scheme, there are normally two lines, one is working line and another one is protection line, both lines are active at all the time.
• One-to-one APS: In this scheme, which looks like the one-plus-one scheme, there is also one working line and one protection line. However, the data are normally sent on the working line until it fails.
• One-to-many APS: This scheme is similar to the one-to-one scheme expect that there is only one protection line for many working lines. When a failure occurs in one of the working lines, the protection line takes control until the failed line is repaired.

Ring network

SONET ring can be used in either a unidirectional or bi-directional configuration. In each case we can add extra rings to make the network self-healing, capable or self-recovery from failure.

• Unidirectional path switching ring: A unidirectional network with two rings, one ring is used as a working ring and other as a protection ring.
• Bidirectional line switching ring: Another alternative in SONET ring network is a bidirectional line switching ring, in this case communication is bidirectional which means that we need two working rings and two protection rings. This means BLSR uses four rings.

Mesh network

Mesh network wit h switches probably give better performance; a switch in a network mesh is called as a cross-connect. A cross-connect switches has input and output ports. In input port the switch takes an OC-n signals and change into STS-n signals, demultiplexes it into the corresponding STS-1 signals, and sends each STS-1 signal to the appropriate output port. An output port takes STS-1 signals coming from different input ports, multiplexes them into an STS-n signal and makes OC-n signals for transmission.

• Two tier model
• Three tier model

Two tier model

Two-tier model is a Java applet applications interact directly with the database. This type of model is referred to as client sever configuration where user is the client and machine that has the database is called as the server.

Three tier model

In this model middle tier is introduced, which is used for various purpose, there are some of the function are used in middle tier, they are

• Collection of SQL statements from the client and handing it over to the database
• Receiving results from the database to the client
• Maintaining control over accessing and updating of the data

SQL Conformance

Structured query language is the standard language used to access relational databases. Unfortunately there are no standards set at present for it. JDBC defines a set of generic SQL type identifiers in the class Java.SQL.Types

Ways of dealing with SQL conformance

JDBC deals with some of the performing SQL conformance, they are

• JDBC API allows any query string to be passed through to an underlying DBMS driver. But there are possibilities of getting an error on some DBMS.
• Provision of ODBC style escape clauses.
• Provision of descriptive information about the DBMS using an interface, Database Meta data.

Different Types of Driver Managers

JDBC contains three components: application, driver manager and driver. The user application invokes JDBC methods to send SQL statements to the database and retrieves result. JDBC driver manager is used to connect java application to the correct JDBC driver. There are four types of JDBC driver. They are

• The JDBC-ODBC Bridge plus ODBC driver
• Native-API partly-Java driver
• JDBC-Net pure Java driver
• Native-Protocol pure Java driver

• Circuit establishment
• Data transfer
• Circuit disconnect

Circuit establishment

In this phase the circuit must be established, when signals are transmitted from one station to other station. This can send information through signals before that the receiving end and sending end must establish their circuit.

Data transfer

In this data transfer phase information can be transmitted from one station to other station through network. The data may be analog signals or digital signals that depends on the nature of the network protocol.

Circuit disconnect

After some time of data transfer, the connection is terminated, generally by the action of one of the two stations. Signals must be propagated to given nodes to deallocate the dedicated resources.

Public circuit switching network

A public telecommunications network can be described using four generic architectural components

• Subscribers
• Subscriber line
• Exchanges
• Trunks

Subscribers

The devices that attach to the network, it is still the case that most subscriber devices to public telecommunications networks are telephones, but the percentage of data traffic increases year by year.

Subscriber line

The link between the subscriber and the network also referred to as the subscriber loop or local loop. Almost all local loop connections use twisted-pair topology. The length of a local loop is typically in a range from a few kilometers to a few tens of kilometers.

Exchanges

The switching centers in the network. A switching center that directly supports subscribers is known as an end office. Typically an end office will support many thousands of subscribers in a localized area.

Trunks

The branches between exchanges, trunks carry multiple voice frequency circuits using either FDM or Synchronous TDM. Before these were referred to as carrier systems.

New iPhone Features for 2008

Continuing the Hit version of Apple 1.1.4 apple has introduced new features for 2008.

Maps

Added features on Map functions, you can do lot of search interactions, you can bookmark and write up a description of each location , you can view the hybrid map of and you can easily locate your destination by pressing the locate button at the bottom of the left screen it immediately takes you the exact location without any hassles.

Added features on SMS

Latest features helps you to send sms to more than one person, what ‘s good is it will keep track of conversation of each sms you have sent and with a push of a button you can easily send it to all the recipients again.

Apple iPhone Internet features

Web clips

For each website you visit at the bottom of the screen you will see a  “ +” button, if you press it you can see the following options.

• Add to Bookmark- You can bookmark any web page or website

• Add to Home screen – This is a new cool feature, you can set Home screen and it will be like a icon on your screen, quickly you can go to the website next time.
• Mail link to this page. – Easy to mail the link to your friends and family.
• Zooming Feature is enhanced now and you can zoom and go to any part of a web page.

Home screen Preferences

This is a new feature of setting up icons on your page according to their importance. If you click any icon for few seconds, you can see all the icons are wobbling little bit, shaking icons, now you can move, drag any icons and set them where you want , you can create any number of icon pages.

Watching films

You can now watch films chapter by chapter without any hassles. You can also browse through the subtitles of each film clip.

These are the latest features of  iPhone introduced in 2008, the content is written with reference to the speech of Mr. Steve Jobs  addressed during Mac world 2008.

• Infrared LANs
• Spread Spectrum LANs
• Narrowband microwave

Infrared LANs:

An individual cell of an IR LAN is limited to a single room, because infrared light does not penetrate opaque walls. Will see some of characteristics details of infrared LANs.

• Strength and weaknesses
• Transmission techniques

Strength and weaknesses:

The infrared has two advantages; the infrared communication can be more easily secured against snooping than microwave and separate infrared installation. The strength of infrared is that the equipment is relatively inexpensive and simple. Infrared data transmission typically uses intensity modulation, so that IR receivers need to detect only the amplitude of optical signals, whereas most microwave receivers must detect frequency.

Infrared LANs have some drawbacks; many indoor environments experience rather intense infrared background radiation, from sunlight and indoor lighting. This ambient radiation appears as noise in an infrared receiver, requiring the use of transmitters of higher power than would otherwise be required and also limiting the range.

Transmission Techniques:

There are three transmission techniques commonly used for IR data transmission. They are

• Directed-beam IR can be used to create point-to-point links.
• Omnidirectional configuration involves a single base station that is with in line of sight of all other station on the LAN.
• Diffused configuration the IR transmitters are focused and aimed at a point on a diffusely reflecting ceiling.

Spread Spectrum LANs:

This type of LAN makes use of spread spectrum transmission technology. In nearly all cases, these LANs operate in the ISM group so that no FCC licensing is required for their use in the US.

Configuration:

In this LANs topology can be either hub or peer-to-peer. I the hub topology, the hub is usually swelled on the maximum and connected to a moral fibre wired LAN to provide connectivity. A peer-to-peer topology is one in which there is no hub. AMAC algorithm such as CSMA is used to control access. This topology is appropriate for ad hoc LANs.

Transmission Issues:

The FCC has authorized two unlicensed application with in ISM band

• Which can operate at up to 1 watt in very low power system
• Which can operate at up to 0.5 watts, the FCC opened this band.

Narrowband microwave LANs:

These LANs operate microwave frequencies but some of these products operate at frequencies that require FCC licensing. It has two-band width they are

• Licensed Narrowband RF has the advantages is that guarantees interference-free communication.
• Unlicensed Narrowband RF can be used for narrowband transmission at lower power 0.5 watts or less.