Understanding Data Communications
Data communication is the transmission of electronic data through multiple media. Media is a coaxial cable, fiber optic, microwave, etc..
Functions Data Communications System
1. Providing Information to the appropriate oaring in a timely manner.
2. Getting a business data while the data is created (online)
3. Data communications system enabling people and businesses that have different geographic locations can berkomunukasi each other.
Three Main Components
1. Source Communications
2. Media Communications
3. Recipient
Understanding Computer Networks
• Networking is a series of several points which are connected by some type of communication channel.
• Komunikasidata network is a collection of data communication circuits which are managed as a single entity.
Terminal
o Microcomputer workstations
Micro general-purpose computer or workstation input / output and CPU smart circuit.
o Remote Job Entry Terminal
Terminals are used in a batch by using punched cards.
o Terminal Facsimile (FAX)
Terminals that can transmit an appropriate image from hard copy documents via telephone lines and satellite circuits around the world
o POS terminals (Point Of Sale)
Terminal commonly used in supermarkets, shops and department stores. Terminal TSB equipped with a system for purchase transactions and allows the database to reflect the status of the company at that time.
o Dumb Terminal / Intelligent
Dumb Terminal is a video terminal that does not take part in the control and processing tasks. Intelligent Terminal is equipped with a CPU. All of the above except the fax terminal can be either dumb terminals or intelligent.
MODEM
Modem is an electronic tool that can modify (modulate) the digital communication between the computer into tones that can be transmitted through telephone lines. The data is received and then converted from voice into digital information.
Cluster Control Unit
This tool is used to make the connection between the terminal which is controlled by other equipment.
Multiplexter
Tool that allows the replacement of some low transmisikecepatan path with high-speed transmission lines.
Front-End Processor
Front-End Processor conduct data communications traffic in and out. Both devices can be different types, common configuration is a special type of minicomputer that functions as a front-end processor and the mainframe as a host.
Host
Host to process incoming messages Datacom after processing the data can be transmitted back to the front-end processor.
Software in Host
Datacom software in the Host called the monitor Telecoummunication
TCM Capabilities
o Placing messages in a particular order of priority in accordance with
o Running the security function by maintaining the activity logs for each terminal
o As an interface between the network and Datacom DBMS
o Dealing with disturbances in the processing
Software in the Front-End Processor
Datacom software in front-end processor called the Network Control Program or NCP
NCP Functions
• Determine whether the terminal using the channel
• Maintain record channel activity
• Change the code used by one type of equipment to another code (IBM DEC)
• Editing functions on the data
• Adding and deleting codes rotation
• Maintaining the history file on the network & statistical
Network Topology
1. Ring Network
• Computers connected to one another invitation to form a circle (ring).
• The data run only one direction around the circle so until dialmat target.
• If one participant in the Ring is destroyed, then the relationship continued to the next computer.
• Jaringanring costs are usually cheaper than the Star and Hybrid network
2. Star Network
• Computer network participants connected with one central computer (Central Device Control).
• Central computer receives data packets from computers on the network and continue to send the packet to the destination computer.
• The advantage of this network is the distance required to send packages from one node to other nodes very quickly.
• Hub in the middle must be highly reliable, when the central station is damaged then the whole network can not be executed.
3. Bus Network
• Computers connected by a cable, data is transferred from one computer to another computer through a bus.
• Every computer on the bus can read and check the data packet addresses of packets apkah TSB TSB in accordance with the address of the computer. When appropriate, the package is taken.
• The loss of one node will not affect the existing network.
4. Hybrid Networks
• Contain more than one topology
• This topology is required to integrate systems of different topology-based
LAN
• Connecting the equipment is limited to small geographic areas.
• Actual distance depends on the LAN can be achieved certain implementations, such as an office space, a single building or group of buildings.
• Implemented for the transfer of data between users in the network and use the equipment together (printer, scanner, fax, plotter, etc.).
OSI (Open Systems Interconnection)
ISO (International Standards Organization), which makes technical recommendations about OSI recommends data communications interface 70 years.
The goal:
To develop a standard framework for computer to computer communications.
There are seven layers:
1. Physical Layer
Physically moving bits of data between the modem and turn on and off the circuit.
2. Data Link Layer
Formatting the data into records called the frame, the detection and correcting errors, running the modem control data flow.
3. Network Layer
Develop, maintain and disconnect communication between the transmission and receiver nodes
4. Transport Layer
Responsible for generating addresses that end users can communicate with the host and ensure that all data packets can be accepted.
5. Session Layer
Managing and supporting the communication dialogue between the two separate locations. These layers start, maintain and terminate each session that contains the frames that have a special activity.
6. Presentation Layer
Receive data from the application layer and data format so that it can be represented to the user or host. Functions that can be run is the encryption of data, code converter, compression and formatting the terminal layer.
7. Application Layer
Controlling user input from a terminal and run user application programs on the host. Equipped with network services like file transfer, terminal emulation, storage into a file server.
Data processing based on its use
1. Batch Processing
Data processing done by the group.
Usually file renewal is done every day.
2. Online Processing
Data processing is conducted separately.
If there is a change of data is done directly.
Real Time System
Real-time system is a special type of online system where transactions are conducted in real time.
Era before the database (Using a traditional file)
• Data are not yet integrated
• There are duplications
• Inconsistent
• Data security is less reliable
• No Standard
Cumulative average Aktivitan Data
• Collecting data
• Verification
• Storage
• Security
• Organizing
• Callings
Secondary storage
1. Sequential storage
Storage media that can be loaded or accessed only with a specific arrangement. The first record should be accessed first, then followed by a record - the next record.
Equipment called the SASD (Serial Access Storage Device). Example: tape
2. Storage Direct
Storage media that can be accessed directly.
Fittings called DASD (Direct Access Storage Device). Example: magnetic disks, optical disks.
Software
Collection of programs - programs used to control the system.
Utilities program
Perform functions required by all users of specific computers. Utility program can perform the function without the need for programming.
Operating Systems
Set the computer process that serves as an interface between users, software and hardware.
Function - the function of the operating system is:
• Scheduling jobs
• Manage hardware and software
• Providing security systems
• Dealing with interruptions
• Maintain usage records
• Allows multiple users to use the computer together.
Language Translator
• First generation language - machine language
• Second Generation Language - assemblers
• Third Generation Languages - Compiler and Interpreter
• Fourth Generation Languages - Natural language
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