NETWORK COMPUTER

The computer network is a collection of computers, printers and other equipment are connected in one unit. Information and data moving through wires or wireless computer network allowing user to exchange documents and data, print on the same printer and together using hardware / software that is connected to the network. Each computer, printer or peripherals connected to the network are called nodes. A computer network can have two, tens, thousands or even millions of nodes.

HISTORY OF COMPUTER NETWORK
     The concept of computer network was born in the 1940s in America of a development project in Model I computer at Bell labs and research group led by Harvard University professor H. Aiken. In the beginning the project merely wanted to use a computer device that must be used together. To do some process without wasting lots of time was made blank successive process (batch processing), so that multiple programs can run in a computer with the rules of the queue.
     In 1950's when the types of computers began to swell until the creation of a super computer, a computer must serve multiple terminals (see Figure 1) was found for the concept of time-based distribution process known as TSS (TimeSharing System), then for the first time form network (network) was applied to the computer. In the TSS system several terminals connected in series to a hostcomputer. In the process of TSS now appears a combination of computer technology and telecommunications technology that was originally developed on their own.

Entering the 1970s, after the workload increased a lot and the price of computer equipment began to seem very expensive, then start to use the concept of the distribution process (Distributed Processing). As in Figure 2, in this process multiple host computers to do a great job in parallel to serve multiple terminals are connected in series in each host computer. In the distribution process is absolutely necessary in-depth blend between computer technology and telecommunications, because in addition to the process that must be distributed, all the host computer must serve the terminals in a single command from a central computer.

Furthermore, when the prices of small computers has begun to decline and the distribution process concept has matured, then the use of computers and networks have started a variety of start dealing with the process and communication between computers (Peer to Peer System) course without going through a central computer. To start developing the local network technology known as LAN. Similarly, when the Internet was introduced, it is mostly a stand-alone LAN started connecting and forming a giant network WAN.

TYPE OF COMPUTER NETWORK
In general, a computer network is divided into five types, namely;
1. Local Area Network (LAN)
Local Area Network (LAN), a privately owned networks within a building or campus-sized to several kilometers. LANs are often used to connect personal computers and workstations in a corporate office or factories in order to use shared resources (ex. printers) and exchange information.

2. Metropolitan Area Network (MAN)
Metropolitan Area Network (MAN), basically a LAN version of the larger and usually use the same technology with LAN. MAN can include corporate offices are located adjacent or also a city and can be used for private purposes (private) or public. MAN capable of supporting data and voice, even may be associated with cable television networks.

3. Wide Area Network (WAN)
Wide Area Network (WAN), its scope covers a wide geographical area, often covering a country or even continent. WAN consists of a collection of machines that aim to run the programs (applications) users.

4. Internet
Actually there are many networks in this world, often using hardware and software that is different. People who are connected to the network often expect to be able to communicate with others connected to other networks. Desires such as these require the relationship between networks that are often not compatible and different. Usually to do this required a machine called the gateway to make connections and perform the necessary translation, both hardware and software. Collection of interconnected networks is called the Internet.

5. Wireless Network
Wireless network is a solution to the communication that can not be done with the wired network. For example, people who want to get information or to communicate despite being on top of a car or plane, it is absolutely necessary because the cable network without a wired connection may not be made in the car or airplane. Currently the network without wires has been rapidly adopted by utilizing satellite services and is able to provide faster access speeds than a wired network.

Topology COMPUTER NETWORK
    Topology is a way to connect a single computer with other computers to form networks. Way that is currently widely used is the bus, token-ring, star and peer-to-peer network. Each of these has a characteristic topology, with its own advantages and drawbacks.
1. BUS topology

Bus topology shown in the schematic above. There are advantages and disadvantages of this type are:
Advantages:                                                    Disadvantages:
- Save cord                                                      - detection and fault isolation is very small
- Layout simple cable                                      - Traffic Density
- Easy to develop                                            - When one client is damaged, then the

- Required repeater for long distance                  network could not function.
  

2. topology Token RING

Token RING topology shown in the schematic above. Token-ring method (often called ring anyway) is how to connect computers so shaped ring (circle). Each node has the same degree. Network will be referred to as a loop, data is sent to each node and each
information received by the node address is checked whether the data for him or not. There are advantages and disadvantages of this type are:
Advantages:                    Disadvantages:
- Save cables                   - Sensitive error

                                        - Development of a network of more rigid
3. STAR topology

Control is centralized, all links must pass through the center of the channel data is all of a node or a client chooses. Central node is called the primary station or a server and other is called the secondary stations or client server. Once the network connection initiated by the server, each server at any time the client can use the network connection without waiting for commands from the server. There are advantages and disadvantages of this type are:
advantages:
- Most flexible
- Installation / change of station is very easy and does not interfere with other parts of the network
- Centralized Control
- Ease of detection and fault isolation / damage
- Ease of network management
Disadvantages:
- extravagant cable
- Need special handling
- Centralized Control (HUB) so the critical element

4. Topology Peer-to-peer Network
Peer meaning co-worker. Peer-to-peer network is a computer network consisting of multiple computers (usually no more than 10 computers with printers 1-2). In the preferred system of this network is the use of programs, data and printers together. Computer users can use the program named Dona in stalled in the computer Dino, and they both can print to the same printer at the same time.
Network system can also be used at home. Computer users who have computers 'ancient', such as AT, and want to buy new computer, say a Pentium II, no need to throw away old computers. He simply put network cards in both computers and then connected with a special cable used for network systems. Compared with the third way, a network system is simpler thus easier to learn and use.