User talk:Yuvi4u

XEV(H1)-BCA(3) 2011 Time : 3 Hours Full Marks – 75 Candidates are required to give their answers in own words as far as practicable. The figues in the margin indicate full marks. Questions are of equal value. Answer two-two questions in each group & One any other. (Answer Five Questions in all group) GROUP-A

1.	What do you mean by Computer Networks ? Describe different modes of data communication ?

Ans:- The computer network means two or more computers are connected through a media link (cables) to exchange information from one computer to another computer.A network is a group of devices connected to each other. Networks may be classified into a wide variety of characteristics: the medium used to transport the data, communications protocol used, scale, topology, benefit, and organizational scope. The modes of data communication are following --- 1. Message - It is the information to be communicated. Popular forms of information include text, pictures, audio, video etc. 2. Sender - It is the device which sends the data messages. It can be a computer, workstation, telephone handset etc. 3. Receiver - It is the device which receives the data messages. It can be a computer, workstation, telephone handset etc. 4. Transmission Medium - It is the physical path by which a message travels from sender to receiver. Some examples include twisted-pair wire, coaxial cable, radiowaves etc. 5. Protocol - It is a set of rules that governs the data communications. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating.

2.	 What is Switching ? Discuss the circuit switching, packet switching and message switching.

Ans:- Every time in computer network you access the internet or another computer network outside your immediate location, your messages are sent through a maze of transmission media and connection devices. The mechanism for moving information between different computer network and network segment is called switching in computer network.

Circuit switching:- Circuit switching is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel (circuit) through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the duration of the communication session. The circuit functions as if the nodes were physically connected as with an electrical circuit.

Packet switching:- Packet Switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. First proposed for military uses in the early 1960s and implemented on small networks in 1968, this method of data transmission became one of the fundamental networking technologies behind theInternet and most local area networks.

Message switching:- In telecommunications, message switching was the precursor of packet switching, where messages were routed in their entirety, one hop at a time. It was first introduced by Leonard Kleinrockin 1961. Message switching systems are nowadays mostly implemented over packet-switched or circuit-switched data networks. Each message is treated as a separate entity. Each message contains addressing information, and at each switch this information is read and the transfer path to the next switch is decided. Depending on network conditions, a conversation of several messages may not be transferred over the same path. Each message is stored (usually on hard drive due to RAM limitations) before being transmitted to the next switch. Because of this it is also known as a 'store-and-forward' network. Email is a common application for Message Switching. A delay in delivering email is allowed unlike real time data transfer between two computers.

3.	Explain K-map and it’s significant ? Discuss 2-variable K-map.

Ans:- The K-map, also known as the Karnaugh map, is Maurice Karnaugh's 1953 refinement of Edward Veitch's 1952 Veitch diagram. A Karnaugh map (K-map) is a pictorial method used to minimize Boolean expressions without having to use Boolean algebra theorems and equation manipulations. A K-map can be thought of as a special version of a truth table .Using a K-map, expressions with two to four variables are easily minimized. Expressions with five to six variables are more difficult but achievable, and expressions with seven or more variables are extremely difficult (if not impossible) to minimize using a K-map. In any K-Map, each square represents a minterm. Adjacent squares always differ by just one literal (So that the unifying theorem may apply: X + X' = 1). For the 2-variable case (e.g.: variables X, Y), the map can be drawn as below. Two variable map is the one which has got only two variables as input. 1.1.1	2-variable map examples The following are all the possible 2-variable, 2 × 2 Karnaugh maps. Listed with each is the minterms as a function of  and the race hazard free (see previous section) minimum equation. •	 m(0); K = 0 •	 m(1); K = A′B′ •	 m(2); K = AB′ •	 m(3); K = A′B •	 m(4); K = AB • m(1,2); K = B′ • m(1,3); K = A′ • m(1,4); K = A′B′ + AB • m(2,3); K = AB′ + A′B •	 m(2,4); K = A • m(3,4); K = B • m(1,2,3); K = A′ + B′ • m(1,2,4); K = A + B′ • m(1,3,4); K = A′ + B • m(2,3,4); K = A + B • m(1,2,3,4); K = 1

4.	Discuss different network devices in details? Ans:-