Data transmission modes

Data transmission modes :-
Data transmission is the process of sending data from one device to another. It consists of sender,  reciever and the medium which carries the information.
There are three modes of data communication  these are

* Simplex transmission mode
* Half duplex transmission modes
* Full duplex transmission modes.
Following are the details of these transmissions modes.

Simplex transmission mode

A simplex mode provide data transmission in only one direction.  One end is sender and the other end is reciever. There are no feedback from the reciever. Reciever can only recieve data and sender can send data. 

Example

*transmission of data/information from keyboard to CPU and CPU to printer 

* Radio and television broadcasting are also simplex transmission. 

2. Half-duplex transmission mode

A half-duplex mode can send and recieve data/information in both direction but not simultaneously. At a time one end is sender and other is reciever.  When sender complte sending data the reciever can send. During data transmission one end is sender and the other is reciever. 

Example

*half-duplex transmission is used in ATM machine for withdraw of cash. 

*internet is the example of half fuplex mode. 

*walkie talkie

3. Full duplex transmission modes

A full duples mode is used to transmit data/information in both direction simultaneously. Sender and reciever can send and recieve data at the same time.  

Example. 

Communication over telephonse line
Communication between computer in a networks are the examples of full duplex transmission modes.

Network Topologies

Network topologies :-  
In computer network,  there are number of ways to join computer to speed up the performance and faults tolerance, which are called as network topologies. In short we can say the physical arrangements of computer system is called topology
There are following types of topilogies. 
* Bus topology
* Star topology
* Ring topology
* Mesh topology
* Tree topology
* Hybrid topology

Bus topology :-

In bus topology all the computer are connecting with the central wire called bus. This bus is used to share medium. Coaxial cable and BNC (british naval connector)  is used in this topology. 

Advantages. 

* it is easy to understand. 

*adding and removing computer are very simple and easy. 

* there is no effect on network if one computer are damange. 

*best topology for small network. 

Disadvantage. 

*security issues 

*if there is any error in the network,  it can not easily be detect. 

*if central wire are damange the whole network stop working

2. Star topology :-

In this topology,  all the computer are connected with the central device called hub/switch. All the computer systems communicate with one another with this central device. Twisted pair cable and rj-45 connector is used in this topology. 

Advantages 

*adding and removing computer very easy. 

* simple and easy to understand and managed. 

*the central device control the flow of data. 

*there is no chance of data collision. 

*faluts can easily detect. 

Disadvantage 

If the central device is shut down whole network will suffer. 

*more expensive to bus topology. 

4. Ring topology :-

In ring topology every device has exactly two neighbors.  All the computers are connected with one another and the last computer are connect with the first computer. All messages travel through a ring in the same direction. Token are passing scheme is used in this topology.  Only one token available on the network. When a node a node want to transmit data it will capture the token and tranmit data.  Twisted pair cable and RJ-45 connector is used in this topology. 

Advantage 

* no data collision. 

*more effective and less costly. 

*best for small network. 

If the central computer fails, any other computer can be made central computer. 

Disadvantage 

*difficult to  troubleshoot. 

*if one computer become defective, it effect the whole network. 

3. Tree topology

Tree topology defines as,  the combination of bus and star topology is known as tree topology.  In tree topology, its has boths Charactistics bus and star topology. Its allow users to have many servers on the network. Tree topology follows a hierarchical pattern whereby each level is connected to the next higher level in a symmetrical pattern. 

Advantages

* highly flexible

*easy to add and remove computer

* supports many hardware and software venders. 

* all computer have better access to network. 

* reduce network traffic

Disadvantage. 

*difficult to configure. 

*if hub stop working the entires system connecting to this network stop working. 

* too expensive

* diffuct to manage and troubleshoot. 

5. Mesh topology. 

IN mesh topology,  all the network nodes are connected to all other nodes. In short all the computer are connected with each other.. Message sent on a mesh network, can take any possible path from source to destination. 

Advantages

* it is most reliable network topology. 

* alternative paths are available in case a path is broken. 

* most secure network. 

*communication fast. 

Disadvantages

* difficult to implement as compare to other topologies. 

* difficult to add new computer.  

* most expensive

Computer Networks

Computer Networks :-
The combination of two or more than two computer in such a way that they can share the resources of each other is called as computer network. 
Charactistics of network :-
Hardware sharing
Software sharing
File sharing
Data communication

Types of Network :-
There are basically three categories of networks LAN, WAN, MAN
Local Area Network (LAN)  :-
A local area network is a digital communication system capable of interconnecting a large no of computers within a limited geographical area. LAN normly operate within a limited area such as an office building or a campus is owned by the using organization. The transmission speed of LAN is very high. 

 WIDE AREA NETWORK (WAN)  :-
A wide are network is a digital communication system.  Which interconnect different sites. This type of communication network may be develop to operate nationalwide or worldwide. In wan the transmission medium used are normaly public system such as telephone lines,  microwave and satellite links.  Its cover a large area so the speed of WAN is less than LAN. 

Metropolitan Area Network (MAN) 

A metropolitan area network is a digital communication system, which interconnects different computer  within a city. MAN is more encompassing than LAN, but smaller than WAN. 

Difference between LAN, MAN and WAN :-

Programming languages and translators

Programming language :- 
     Language is a communication medium through which we can express our feelings, thoughts and emotions. 
 The language thorugh which we can communicate a computer is called computer language. Computer language are helpful for creating software and programs. 
Types of computer languages :-
* Low level language
*High level language. 

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Low level language :- 
  Although compuger can be programmed to understand many diffrent computer languages, there is only language understood by the computer without using translation program. This language is called the low level language or machine language. Its normly written as strings of binary 1s and 0s. The low level language is far from humans and near to computer system. Computer can directly understand low level language.  The computer can execute program written in machine language very fast. 
High level language :-
High level language enable the programmer to write instructions using English words and familar mathematical symbols. So it becomes easier for him to concentrate on the logic of his problem rather than getting involved in programming details. It is easy for human and for from computer. So it os translated into many machine language instructions. A language translator are used to translate high level language into machine language.  C,  C++ , PASCAL,  COBOL are some examples of high level language. 

Procedural language :-

The introduction of more user friendly programming language resulted in a quantum leap in programmer convenience. These early languages were procedure languages. Which require programmers to solve programming problems using traditional programming logic. Example of procedurallanguage are COBOL & FORTRAN both introduced in late 1950s but still popular today. 

Object oriented language (OOPS) 

In procedural language the emphasis is on what is done. In object oriented language the emphasis is on the object of the action. The structure of oops makes programs easier to design and understand. Example of object oriented language include smalltalk, Java, and C++.

Database Query Language :-

These language are based on special kind of database called a relational database. Many database managements programs in today computer world claim to be relational but actually are not.  SQL,  MYSQL are example of database query language. 

Language translators

A software that is used to convert high level language into machine language is called language translator. 

There are following types of translator

*Compiler

*Interpreter 

*Assembler

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Compiler:-

Computer hardware can only understand the machine or hardware language. When we write a program in high level language it is necessary to convert the instructions into machine language. Thus a compiler is a translating program that translte the instructions of a high level language into machine language.  A compiler can translate only those source code which have been written in the language for which the compiler is meant. 

Interpreter :-

An interpreter is another type of translator used for translating high level language into machine code. It takes one statement of a high level language and translates it into machine code. Which is immediatly executed. 

Assembler :-

This is type of translator that work in the same way as compiler and interpreter work. It is a program. Which translate an assembly language program to its machine language. In short assembler are software which are used to convert assembly language into machine language

COMPUTER BUSES

Computer Bus
In computer architecture,  a bus is a system that is use to transfer data from one components to another inside a computer. A bus can logically connect several peripherals over the same set of wires. Each bus defines its set of connectors. Commonly three types of busses used in computer. 
* Data bus
* Address bus
* Control bus
Following are the details of thats. 

*Data bus :- 
It is used to carry data signals.  Numbers which we want to ss or the strings which want to compare will travel on data bus. To transfering data from main memory to cpu and then from CPUto any other output data bus is used. 
*Address bus :- 
It is used to carry address signals,  address of a memory location or a port where an input / output device are attached.
*Control bus :- 
It is used to carry control signals. Control signal are used to control all the activities of the computer system. Example of control sognals are read/write enable/disable etc

hardware and software

software

a set of instruction that tells the computer what to do..
a set of instruction given to the computer to solve a problem is called software.
software is also called program.different software are used to perform different tasks.computer are performs those task which are given to computer.

hardware.

the physical component of computer system is called hardware.hardware can be seen and touched.

    a software connot execute any task without hardware and a hardware is useless with out software.a computer work only when hardware and software are combined

types of software

software are divided into following categories

1:- System software

2:- Application software...

System software

System software is set of programs that are used to control and manage the computer hardware.it control the basic operations as follow.

* Saving data on disk

* Making computer ro work for us

* Printing a documents etc

Examples of system software...

operating system ( windows , UNIX , DOS etc )

Device drivers

Utilities programs

Application software

Application software are used to perform various applications on computer system.it help a computer user to perform specific tasks.People use application software according to their use.

Ms word , adobe photoshop are some example of application software.

Storage devices

The devices used for storage and retrieval of data for the later use are called storage devices. storage devices are commonly classified into two categoris.

1:- PRIMARY STORAGE

2:- SECONDARY STORAGE

Storage devices are the computer hardware used to remember/store data.

1:- PRIMARY STORAGE...

             

All data and programs used unit is called internal storage, because it usually occupies the same physical enclosures as the CPU.

The development of-semi-conductor silicon memory chips helped the computer to retain data and programs’ instruction. The instruction retained in the chips can initiate input/output operations and processing functions. Following clips are used as primary storage device.

RAM (Random Access Memory)

ROM (Read Only Memory)

2:- SECONDARY STORAGE....

secondary storage also called auxiliary storage or mass storage devics. it is used to store data and instructions for future use. these devices are available with high capacity as compare to primary storage devices. secondary storage devices are widely used to store large amount of data for future use.

1. Hard Drive Disk
2. Floppy Disk
3. Tape
4. Compact Disc (CD)
5. DVD and Blu-ray Discs
6. USB Flash Drive
7. Secure Digital Card (SD Card)
8. Solid State Drive (SSD)
9. Cloud Storage

PRIMARY STORAGE VS SECONDARY STORAGE DEVICES

TYPES OF PRIMARY STORAGE DEVICE :-

There are two main types of primary storage devices these are 

RAM

ROM

RAM (Random Access Memory)

 RAM (random access memory) is a hardware device that allows information to be stored and retrieved on a computer. RAM is usually associated with DRAM, which is a type of memory module. Because information is accessed randomly instead of sequentially like it is on a CD or hard drive, access times are much faster. However, unlike ROM, RAM is a volatile memory and requires power to keep the data accessible. If the computer is turned off, all data contained in RAM is lost.

Types of RAM

Over the evolution of the computer, there have been different variations of RAM. Some of the more common examples are DIMM, RIMM, SIMM, SO-DIMM, and SOO-RIMM.

ROM (Read Only Memory)

Read-only memory (ROM) is a type of storage medium that permanently stores data on personal computers (PCs) and other electronic devices. It contains the programming needed to start a PC, which is essential for boot-up; it performs major input/output tasks and holds programs or software instructions.

Because ROM is read-only, it cannot be changed; it is permanent and non-volatile, meaning it also holds its memory even when power is removed. By contrast, random access memory (RAM) is volatile; it is lost when power is removed.

There are numerous ROM chips located on the motherboard and a few on expansion boards. The chips are essential for the basic input/output system (BIOS), boot up, reading and writing to peripheral devices, basic data management and the software for basic processes for certain utilities.

Types of ROM

ROM may sometimes be called maskROM (MROM). MROM is a form of read-only memory that is static and programmed into an included circuit by the manufacturer. Solid-state ROM, the oldest type of ROM, is an example of maskROM. With the original ROM, since it was truly read-only, it had to be removed and physically replaced in order to change any of its contents.

However, new types of ROM have emerged that are still non-volatile, but can be reprogrammed; these types are categorized as programmable read-only memory (PROM). PROM can be used to update firmware, such as BIOS, through the utilization of installation software.

Types of PROM include:

• Ultraviolet-erasable ROM (UV-ROM) - ROM whose contents can be erased using ultraviolet light, and then reprogrammed.
• Erasable programmable ROM (EPROM) - A type of ROM that is programmed using high voltages and exposure to ultraviolet light for about 20 minutes.
• Electrically-erasable programmable ROM (EEPROM) - Often used in older computer chips and to control BIOS, EEPROM can be erased and reprogrammed several times while enabling the erase and writing of only one location at a time. Flash memory is an updated version of EEPROM that allows numerous memory locations to be changed at the same time.
  TYPES OF SECONDARY STORAGE DEVICES

• Hard Disk Drive

  A hard disk drive (also known as a hard drive, HD, or HDD) can be found installed in almost every desktop computer and laptop. It stores files for the operating system and software programs, as well as user documents, such as photographs, text files, and audio. The hard drive uses magnetic storage to record and retrieve digital information to and from one or more fast-spinning disks.

  2. Floppy Disk

  Also know as a diskette, floppy, or FD, the floppy disk is another type of storage medium that uses magnetic storage technology to store information. Floppy disks were once a common storage device for computers and lasted from the mid-1970's through to the start of the 21st century. The earliest floppies were 8-inch (203 mm) in size, but these were replaced by 5 ¹⁄₄-inch (133 mm) disk drives, and finally a ​3 ¹⁄₂ inch (90 mm) version.

  3. Tape

  In the past, magnetic tape was often used for digital data storage, because of its low cost and ability to store large amounts of data. The technology essentially consisted of a magnetically thin coated piece of plastic wrapped around wheels. Its relative slowness and unreliability compared to other data storage solutions has resulted in it now being largely abandoned as a media.

  4. Compact Disc (CD)

  The compact disc, known for short as a CD, is a form of optical storage, a technology which employs lasers and lights to read and write data. Initially compact discs were used purely for music audio, but in the late 1980's they began to be also used for computer data storage. Initially, the compact discs that were introduced were CD-ROM's (read only), but this was followed by CD-R's (writable compact discs) and CD-RW's (re-writable compact discs).

  
  

  5. DVD and Blu-ray Discs

  The DVD (digital versatile disc) and Blu-ray disc (BD) are formats of digital optical disc data storage which have superseded compact discs, mainly because of their much greater storage capacity. A Blu-ray disc, for example, can store 25 GB (gigabytes) of data on a single-layer disc and 50 GB on a dual-layer disc. In comparison, a standard CD is the same physical size, but only holds 700 MB (megabytes) of digital data.

  6. USB Flash Drive

  Also known as a thumb drive, pen drive, flash-drive, memory stick, jump drive, and USB stick, the USB flash drive is a flash memory data storage device that incorporates an integrated USB interface. Flash memory is generally more efficient and reliable than optical media, being smaller, faster, and possessing much greater storage capacity, as well as being more durable due to a lack of moving parts.

  7. Secure Digital Card (SD Card)

  A common type of memory card, SD cards are used in multiple electronic devices, including digital cameras and mobile phones. Although there are different sizes, classes, and capacities available, they all use a rectangular design with one side "chipped off" to prevent the card from being inserted into the camera or other device the wrong way.

  8. Solid State Drive (SSD)

  A solid state drive uses flash memory to store data and is sometimes used in devices such as netbooks, laptop, and desktop computers instead of a traditional hard disk drive. The advantages of an SSD over a HDD include a faster read/write speed, noiseless operation, greater reliability, and lower power consumption. The biggest downside is cost, with an SSD offering lower capacity than an equivalently priced HDD.

  9. Cloud Storage

  With users increasingly operating multiple devices in multiple places, many are turning to online and cloud computing solutions. Cloud computing basically involves accessing services over a network via a collection of remote servers. Although the idea of a "cloud of computers" may sound abstract to those unfamiliar with this metaphorical concept, in practice it can provide tremendous storage solutions for devices that are connected to the internet.