QUESTION: 29

Which of the following OSI layers is responsible for protocol conversion, data encryption/decryption, and data compression?

Presentation layer
Network layer
Data-link layer
Transport layer

Answer(s): A

Explanation:

The Presentation layer is a part of an operating system that converts incoming and outgoing data from one presentation format to another. It is responsible for protocol conversion, data encryption/decryption, expanding the graphics command, and data compression. It defines the format of data being sent and any encryption that may be used, and makes it presentable to the Application layer. It presents the data in a uniform format and masks the difference of data format between two dissimilar systems. It also translates the data from an application to the network format. The Presentation layer is the best layer for cryptography. It is sometimes also called the Syntax layer.
Answer option C is incorrect. The data-link layer sends data frames from the network layer to the physical layer. On the receiving end, it packages the raw bits from the physical layer into data frames. The data-link layer is responsible for error free transfer of data frames.
Answer option B is incorrect. The network layer controls the operation of subnet, deciding which physical path the data should take, based on network conditions, priority of service, and other factors. Routers work on the Network layer of the OSI stack.
Answer option D is incorrect. The Transport Layer of TCP/IP model is responsible for end-to-end message transfer capabilities independent of the underlying network, along with error control, segmentation, flow control, congestion control, and application addressing (port numbers). End to end message transmission or connecting applications at the transport layer can be categorized as either connection-oriented, implemented in Transmission Control Protocol (TCP), or connectionless, implemented in User Datagram Protocol (UDP).

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QUESTION: 30

Samantha works as a Web Developer for BlueWell Inc. She develops a Web application using Visual InterDev. She wants to group a series of HTML elements together so that an action can be performed collectively on them.
Which of the following tags will Samantha use to accomplish this?

GROUP
SPAN
BODY
DIV

Answer(s): D

Explanation:

DIV is an HTML tag that groups a series of elements into a larger group. It can be used when an action needs to be performed collectively on the grouped elements. The DIV tag acts as a container for other elements.
Answer option B is incorrect. The SPAN tag is used within an element to group a part of it. For example, this tag can be used to group a few sentences from within a paragraph, so that a particular action can be performed only on them.
Answer option C is incorrect. The BODY tag is used to specify the beginning and end of the document body.Answer option A is incorrect. There is no tag such as GROUP in HTML.

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QUESTION: 31

Fill in the blank with an appropriate word.
A ______________is a Web site that is used for searching a particular subject provided as a keyword.

search engine

Answer(s): A

Explanation:

A search engine is a Web site that is used for searching a particular subject provided as a keyword. The search engine searches for the subject and provides the links to those Web sites that contain the subject. Search engines use databases and programs to collect information from the Web sites. This information is indexed by the search engines.

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QUESTION: 32

Which of the following signals is transmitted on the internal bus structure of the motherboard and processor or across a network and represents the binary value of the transmitted data?

Digital signal
Carrier signal
Off-hook signal
Analog signal

Answer(s): A

Explanation:

A digital signal is one in which the original information is converted into a string of bits before being transmitted.
A radio signal, for example, will be either on or off. Digital signals can be sent for long distances and suffer less interference than Analog signals. The communications industry worldwide is in the midst of a switch to digital signals. Sound storage in a compact disk is in digital form. This type of signal is transmitted on the internal bus structure of the motherboard and processor or across a network. It represents the binary value of the transmitted data. The signal pattern of the data consists of a series of high and low frequencies.A simplified depiction of a digital signal is shown in the below figure.
Answer option D is incorrect. An Analog or analogue signal is any continuous signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are meaningful. Analog is usually thought of in an electrical context; however mechanical, pneumatic, hydraulic, and other systems may also convey analog signals.An analog signal uses some property of the medium to convey the signal's information. For example, an aneroid barometer uses rotary position as the signal to convey pressure information. Electrically, the property most commonly used is voltage followed closely by frequency, current, and charge.For example, in sound recording, fluctuations in air pressure (that is to say, sound) strike the diaphragm of a microphone which induces corresponding fluctuations in the current produced by a coil in an electromagnetic microphone, or the voltage produced by a condenser microphone. The voltage or the current is said to be an 'analog' of the sound.
A simplified depiction of analog signal is shown in the figure below.
Answer option B is incorrect.
A carrier signal is a transmitted electromagnetic pulse or wave at a steady base frequency of alternation on which information can be imposed by increasing signal strength, varying the base frequency, varying the wave phase, or other means. This variation is called modulation. With the advent of laser transmission over optical fiber media, a carrier can also be a laser-generated light beam on which information is imposed.Types of analog modulation of a carrier include amplitude modulation (AM), frequency modulation (FM), and phase modulation. Types of digital modulation include varieties of pulse code modulation (PCM), including pulse amplitude modulation (PAM), pulse duration modulation (PDM), and pulse position modulation (PPM).
Answer option C is incorrect. An off-hook signal is an informational signal generated by analog phones.
A receiver off-hook signal is used to indicate that a telephone receiver is placed off- hook and there is no activity on that line. Since an analog phone considers dialing to be the only detectable "activity", a voice dialog between a caller and a voice recognition system does not normally disengage the connection.

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