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Unbelievable Facts About Data Communication.

Data Communication:



 Since the purpose of Computers, data communications and networks is to process data into information. Data are stored inside a computer and transmitted on a communications system in the form of binary digits, or bits. The digits are either 1's or O's and are coded in
accordance with the binary (base 2) number system.
The binary bits inside a computer are represented by the level of a polarity of electrical signals. A high-level signal within a storage element in the computer could represent a 1; low-Level signal a 0. These elements are strung together to form numbers and characters, such as the number 6 or the letter A, in accordance with established codes.
Data are transmitted along the communications path (often the telephone network) between computer-oriented devices using electrical signals and bit sequence to represent numbers and characters. In some instances, the data representation may be by light signals, as in optic fibers. The bit representations depict user data and control data. The control data are used to manage the communications network and the flow of the user data.
depicts how the data move from a sending computing device, through the communications medium, and into a receiving computer device. The order should be aware that the binary data code is converted to base 10 for human consumption when it is displayed on terminals and printouts.
The term bps refer to the number of binary bits per second that are transferred through a communication path or component. If a 2,400 bit/s line uses an 8-bit code to represent a number of character, then the character per second rate is 300 (2,400/8 =300). The majority of communications speeds are quoted in bit/s rates.
It should be emphasized that a bit traveling down a communications path, as in is actually a representation of the electrical/electromagnetic or optical state of the line for a certain period of time. The bit 1 may be depicted by placing a negative voltage on the line for a few fractions of a second arid a 0 could be represented by a low-level signal positive voltage for the same period of time.


Transmission Characteristics  A general knowledge of the characteristics of electrical transmission is essential if the reader is to gain an understanding of data communIcations, Line capacity error Control techniques, communications software, and many other network components are all analyzed and designed around the capabilities and limitations of electricity.the data are transmitted on a communications channel by the alteration of an electrical signal to represent 1's and O's. The electrical signal state manifests itself by either the signal level or some other property of the complex electrical signal. The movement of the signal over its transmission path is referred to as signal propagator. On a wire path, signal propagation is a flow of electrical current. Radio transmission between computer sites without the use of wires is accomplished by emitting an electrical signal that propagates as an electromagnetic wave.
 The term baud is another commonly used in data communications. This term describes the rate of change of the signal on the line, that is, how many times (per second) the signal changes its pattern. As a simple example, the sending device assembles the bits into groups of two and then modifies the oscillating waveform (that is. changes the signal state) to one of four amplitudes to represent any combination of 2 bits (00, 01, 10, II). In this example, the bit transfer rate across the Communications path is twice the baud(or rate of signal change). Most modems today use up to 8 bits per baud to achieve greater signal transfer capacity.
The process is called modulation. This term means that the data stream changes or modulates the signal on the communications path (channel or link).
The signal is also distinguished by its frequency or number of complete oscillations of the waveform in a given time. Frequency is measured in oscillation per second. The electrical industry has defined the unit of I hertz (Hz) to mean one Oscillation per second.
The other term used to describe frequency is cycles per second( ) frequency of the wave has no relation to the amplitude. Signals can have many different combinations of the two. The amplitude indicates the signal level and the amount of negative or positive voltage, while the frequency indicates the rate (in Hertz) of the signal oscillation. The phase of the signal describes the point to which the signal has advanced In its cycle. the phases of the signal are identified as the beginning of the cycle. 1/4 of the cycle,1/2 of the cycle,3/4 of the cycle, and the completion of the cycle. The wave can also be labeled with degree markings like that of a sine wave or a 36O circle. The sine wave is so named because the wave varies in the same manner as the trigonometric sine function. The sine wave is derived from circular motion. The amplitude of the wave increases to a maximum at 90degrees, in the same manner, that the sine of an angle of rotation increases to a maximum of 90°. Since a complete cycle represents a 360° rotation around the circle. 1/4 of a cycle point represents a phase value of 90 degrees.
 The wave depicts the signal at its maximum strength at two points in the cycle. One-half of the cycle is represented by a positive voltage and the other one-half by a negative voltage. The changing voltage state results in electrical charges changing their direction of flow down the wire circuit. The voltage continuously varies its amplitude and periodically reverses its polarity. The nature of the charge is the only difference. The strength, either positive or negative. is the same at the two peaks in the cycle.
Transmission capacity, speed, and delay :
The transmission capacity, stated in bits per second (bit/s), of a communications system, is quite important because response time and throughput for the user applications running on a computer depend on the capacity of the system. For example, a 4,800-bit/s line will provide twice the capacity of a 2,400-bit/s line and result in increased throughput and better response time.
The telephone network is designed to carry voice, which is a low-bandwidth signal. Adequate voice fidelity requires a frequency spectrum of about 3 kHz. The frequency spectrum for voice-grade circuits does not allow for a high rate of bits per second to be transmitted.
The limiting factors on transmission capacity are the bandwidth, signal power, and noise on the conductor. An increased signal power can indeed increase the line capacity and also provide for greater distance for the propagation of the signal. However, excessive power may destroy components in the system and/or may not be economically feasible.
The noise on a line is a problem that is inherent to the line itself and cannot be eliminated. Noise (called thermal, Gaussian, white, or background noise) results from the constant, random movement of electrons on the conductor and provides a limit to the channel capacity. The hiss you hear on a telephone line is such a noise. Any electrical conductor is a source of a noise. The power of the noise is proportional to the bandwidth, so in lncre*aod b.ndwIdtb will also contain additional noise. An electronic technique known— filtering Is used to reduce the added noise



 Since the purpose of Computers, data communications and networks is to process data into information. Data are stored inside a computer and transmitted on a communications system in the form of binary digits, or bits. The digits are either 1's or O's and are coded in
accordance with the binary (base 2) number system.
The binary bits inside a computer are represented by the level of a polarity of electrical signals. A high-level signal within a storage element in the computer could represent a 1; low level signal a 0. These elements are strung together to form numbers and characters, such as the number 6 or the letter A, in accordance with established codes.
Data are transmitted along the communications path (often the telephone network) between computer-oriented devices using electrical signals and bit sequence to represent numbers and characters. In some instances, the data representation may be by light signals, as in optic fibers. The bit representations depict user data and control data. The control data are used to manage the communications network and the flow of the user data.
depicts how the data move from a sending computing device, through the communications medium, and into a receiving computer device. The order should be aware that the binary data code is converted to base 10 for human consumption when it is displayed on terminals and printouts.
The term bps refer to the number of binary bits per second that are transferred through a communication path or component. If a 2,400 bit/s line uses an 8-bit code to represent a number of character, then the character per second rate is 300 (2,400/8 =300). The majority of communications speeds are quoted in bit/s rates.
It should be emphasized that a bit traveling down a communications path, as in is actually a representation of the electrical/electromagnetic or optical state of the line for a certain period of time. The bit 1 may be depicted by placing a negative voltage on the line for a few fractions of a second arid a 0 could be represented by a low-level signal positive voltage for the same period of time.


Transmission Characteristics  A general knowledge of the characteristics of electrical transmission is essential if the reader is to gain an understanding of data communIcations, Line capacity error Control techniques, communications software, and many other network components are all analyzed and designed around the capabilities and limitations of electricity.the data are transmitted on a communications channel by the alteration of an electrical signal to represent 1's and O's. The electrical signal state manifests itself by either the signal level or some other property of the complex electrical signal. The movement of the signal over its transmission path is referred to as signal propagator. On a wire path, signal propagation is a flow of electrical current. Radio transmission between computer sites without the use of wires is accomplished by emitting an electrical signal that propagates as an electromagnetic wave.
 The term baud is another commonly used in data communications. This term describes the rate of change of the signal on the line, that is, how many times (per second) the signal changes its pattern. As a simple example, the sending device assembles the bits into groups of two and then modifies the oscillating waveform (that is. changes the signal state) to one of four amplitudes to represent any combination of 2 bits (00, 01, 10, II). In this example, the bit transfer rate across the Communications path is twice the baud(or rate of signal change). Most modems today use up to 8 bits per baud to achieve greater signal transfer capacity.
The process is called modulation. This term means that the data stream changes or modulates the signal on the communications path (channel or link).
The signal is also distinguished by its frequency or number of complete oscillations of the waveform in a given time. Frequency is measured in oscillation per second. The electrical industry has defined the unit of I hertz (Hz) to mean one Oscillation per second.
The other term used to describe frequency is cycles per second( ) frequency of the wave has no relation to the amplitude. Signals can have many different combinations of the two. The amplitude indicates the signal level and the amount of negative or positive voltage, while the frequency indicates the rate (in Hertz) of the signal oscillation. The phase of the signal describes the point to which the signal has advanced In its cycle. the phases of the signal are identified as the beginning of the cycle. 1/4 of the cycle,1/2 of the cycle,3/4 of the cycle, and the completion of the cycle. The wave can also be labeled with degree markings like that of a sine wave or a 36O circle. The sine wave is so named because the wave varies in the same manner as the trigonometric sine function. The sine wave is derived from circular motion. The amplitude of the wave increases to a maximum at 90degrees, in the same manner, that the sine of an angle of rotation increases to a maximum of 90°. Since a complete cycle represents a 360° rotation around the circle. 1/4 of a cycle point represents a phase value of 90 degrees.
 The wave depicts the signal at its maximum strength at two points in the cycle. One-half of the cycle is represented by a positive voltage and the other one-half by a negative voltage. The changing voltage state results in electrical charges changing their direction of flow down the wire circuit. The voltage continuously varies its amplitude and periodically reverses its polarity. The nature of the charge is the only difference. The strength, either positive or negative. is the same at the two peaks in the cycle.
Transmission capacity, speed, and delay :
The transmission capacity, stated in bits per second (bit/s), of a communications system, is quite important because response time and throughput for the user applications running on a computer depend on the capacity of the system. For example, a 4,800-bit/s line will provide twice the capacity of a 2,400-bit/s line and result in increased throughput and better response time.
The telephone network is designed to carry voice, which is a low-bandwidth signal. Adequate voice fidelity requires a frequency spectrum of about 3 kHz. The frequency spectrum for voice-grade circuits does not allow for a high rate of bits per second to be transmitted.
The limiting factors on transmission capacity are the bandwidth, signal power, and noise on the conductor. An increased signal power can indeed increase the line capacity and also provide for greater distance for the propagation of the signal. However, excessive power may destroy components in the system and/or may not be economically feasible.
The noise on a line is a problem that is inherent to the line itself and cannot be eliminated. Noise (called thermal, Gaussian, white, or background noise) results from the constant, random movement of electrons on the conductor and provides a limit to the channel capacity. The hiss you hear on a telephone line is such a noise. Any electrical conductor is a source of a noise. The power of the noise is proportional to the bandwidth, so in lncre*aod b.ndwIdtb will also contain additional noise. An electronic technique known— filtering Is used to reduce the added noise



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JavaScript DialogBoxes

Dialog Boxes:

 

These dialog boxes appear, as Separate window and their content depends on the information provided by the user. This content is independent of the text in the HTML page containing the javascript script and does not affect the content of the page in any Way.

Three types of dialog boxes provided by javascript are: 

1. Alert dialog box
2. prompt dialog box
3. Confirm dialog box. 

1.The Alert Dialog Box :

  1. This is the simplest of all and is used to display a small amount of text to the user. the javascript alert( ) method takes a string as an argument and displays an alert dialog box in the browser window when invoked by JavaScript code.
  2. The alert dialog box displays the string passed to the alert( ) method as a message, as well as an OK button. The JavaScript and the HTML program, in which this code snippet is held, will not continue processing until the 0k button is clicked(that is until dismissed).
  3. The alert dialog box can be used to display a cautionary message or display some information.
  4. A message is displayed to the user when incorrect information is keyed in a form like an invalid password.An invalid result is the Output of a calculation.
  5. A warning that a service is not available on a given date/time.

Syntax

alert(”message”):
as in:
alert("ClIck OK to continue”) 

Example

To display the user the sum of two numbers.

FIle Name : AlertDemo.html 

<HTML>
<BODY>
<SCRIPT>
var x= 10;
var y =20.50;
alert("Sum is" +(x + y));
document.writeln(x + y);  //this statement is not printed uztil alert dialogbox dismissed
</SCRIPT>
</BODY>
</HTML>

2. Prompt Dialog Box :

  1. As seen in the previous program, the alert dialog box simply displays information in a browser and does not allow any interaction with the user. 
  2. With prompt dialog box user can enter some data that can be read into a program(like scanf function).
  3. The prompt dialog box displays a specified message. In addition, the prompt dialog box also provides a single data entry text box in which the user can enter some data.  

The prompt dialog box displays the following.

  1. Displays a predefined Message.
  2. Displays a text box for user input.
  3. Displays an OK & Cancel push buttons.
  4. The prompt dialog bo also causes program execution to halt until user action takes place(modal dialog box).
  5. This could be the OK button being clicked, or the CANCEL button is clicked, which causes the following action to take place.
  6. Clicking on the OK button causes the text typed inside the textbox to be passed to the program environment (i.e JavaScrip).
  7. Clicking on the CANCEL button causes a NULL value to be passed to the environment. When the prompt( ) method is used a instantiate and use a dialog box the method requires two blocks of information.
  8. A message to be displayed as a prompt to the User.
  9. Any message to be displayed in the textbox. by default(this is optional)


Syntax 

prompt"Message" “Default value”);
as in
prompt(” Enter your favorite color”, "Blue");
A default value, Blue, is displayed by default in the text box which user can change if he wants. The value that user keys into the textbox on the prompt dialog box is accepted and can be stored variable.

Example 

To access two numbers from the user and displays their product.

File Name : PromptDemo.HTML
<HTML>
<BODY>
<SCRIPT>
var fn = prompt("Enter first number" ,"10");
var sn = prompt("Enter second number","2O.5");
document.writeln(fn*an);
</SCRIPT>
</BODY>
</HTML> 


Confirm Dialog Box:
 
JavaScript Provides a third type of a dialog box, called the confirm dialog box. As the name indicates, this dialog box serves as a technique for confirming user action. 


The confirm dialog box displays the following information:

  1. A pre-defined message
  2. OK & Cancel button.
  3. The confirm dialog box does not allow any user activities until the dialog box is dismissed(modal).
  4. Clicking on the OK button causes TRUE to be passed to the program that called the confirm dialog box.
  5.  Clicking on the CANCEL button causes FALSE to be passed to the program that called the confirm dialog box.

Syntax

confirm("message");
as in
confirm("Are you sure of your order?");

Example 

To display a message if user confirms.
File Name: ConfirmDemo.html
<HTML>
<BODY>
<SCRIPT>
var qty = prompt("How many Reliance shares you would like purchase","200");
if(confirm("Are you sure, shall I place order with Stock exchange?")); 
{
document.writeln("Your order of" +qty+ "shares is confirmed");
}
</SCRIPT>
</BODY>
</HTML>



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Cybernetics Protector Tutorial Part 1



Cybernetics Protector Introduction :





 The secret intelligence service is constantly using underground agents to solve modern cases and to remove criminal companies.  secret intelligence agencies and their agents are communicating safely by this  software



Existing System:



In the current system, everything is done manually, for example Maintaining/generating and producing/maintaining evidence for specific authority is performed by most people.



Disadvantages of Existing System:

1.The Burden will increase.

2.We will not provide proper security for the data especially to evidence which is very confidential.

3.This is a time-consuming process.



To overcome all the above disadvantages existing in the existing system we will propose a new system as mentioned below.



Proposed System: 


In the proposed system, all the activities performed by humans in the existing system are computerized in the proposed system. The Secret Intelligence Agency always uses secret agents to solve complex cases and to overthrow criminal companies. Secret intelligence agencies and their agents are communicating in a secure way through this software

Study of the system:

To provide flexibility to the users, the interfaces are developed that are accessible by the browser. The GUI’S at the highest level are classified as.
1.Administrative user interface
2.The operational or generic user interface


    
administrative interface 'focus on consistent data needed for data acquisition. These interfaces help operators along with extensive data search capabilities in all transaction states, such as data interface, data removal, and data updating.Operation or Simple User Interface' help the end-users of the system in transactions through existing data and services. The functional user interface also helps ordinary users in maintaining their own information in a convenient manner, as per flexibilities.

Feasibility Study:

Feasibility Report:
 The preliminary investigation examines project feasibleness, the probability of the system are helpful to the organization. the most objective of the feasibleness study is to check the Technical, Operational and Economical practicability for adding new modules and debugging recent running system. All systems area unit feasible if they're given unlimited resources and infinite time. 
There area unit aspects of the feasibleness study portion of the preliminary investigation:
  1. Technical Feasibility
  2. Operation Feasibility
  3. Economical Feasibility




     
 
     
     


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