Storage devices

What is a Storage Device?   

A storage device is a computer hardware component that writes and reads data to and from storage media. Writing data means recording data from memory to a storage medium. Reading or retrieving data means transferring data from the storage medium into the computer’s memory for use by the operating system or application program.       

Levels of Data Processing.

Manual Data Processing: In manual data processing, data is processed manually without using any machine or tool to get the required result. In manual data processing, all the calculations and logical operations are manually performed on the data.

Similarly, data is manually transferred from one place to another. This method of data processing is very slow and errors may occur in the output.

Mechanical Data Processing: In mechanical data processing, data is processed by using different tools like calculators or other mechanical devices. This method of data processing is faster and more accurate than manual data processing.

Electronic Data Processing: It is a modern technique to process data. The data is processed through a computer. Data and set of instructions are given to the computer as input and the computer automatically processes the data according to the given set of instructions.

The computer is also known as an electronic data processing machine. This method of processing data is very fast and accurate. Nowadays, the data is processed and analyzed through computers. For example, the results of students are prepared through the computer; in banks accounts of customers are processed through computers, etc.

Functions of Operating System.     

Booting a Computer: The operating system consists of a supervisor portion and a set of system programs. When the computer is switched on, the supervisor portion of the operating system (known as kernel) is loaded in the RAM from the disk. This process to start or restart a computer is called the booting process.

User interface: User interface means how the user interacts with the computer to perform various tasks. The user runs the application programs, opens the document, enters the data, and prints the output reports.

Running Programs: The operating system also provides the interface between the programs and the user. Through a program, the user accesses other computer resources such as printers, backing storage, or other application programs.

Managing Files: The data and programs are stored permanently on the disk for future use.

Memory Management: The memory unit has a very important role in data processing. The processor takes data and program instructions from RAM during processing. The data and programs are loaded from disk into RAM.

Scheduling Jobs: A job is an activity or operation that a processor performs. It may be receiving data from an input device, sending output to an output device or loading data from the disk into RAM.

Configuring Devices: The functions of devices attached. The computer is controlled by special system software called device drivers. The device driver tells the operating system how to communicate with a device.

Establishing Internet Connection: The operating system also provides means to establish a connection between your computer and the ISP (Internet Service Provider) Server. Some operating systems also have built-in browser programs used to access information on the Internet.

Controlling Network: Some Operating systems are specially developed, for networking. These operating systems are called network operating systems or NOSs. A network operating system organizes and coordinates multiple users and makes it possible to access and share resources on the network.

Task Management: A computer can perform many tasks at a time. For example, in word processing, it accepts input data, stores data on the disk, and prints out a document simultaneously.

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Types of Data Transmission Modes.

Parallel Transmission: In parallel transmission, bits of data flow concurrently through separate communication lines. Parallel transmission is shown in the figure below. The automobile traffic on a multi-lane highway is an example of parallel transmission.

Inside the computer binary data flows from one unit to another using parallel mode. If the computer uses a 32-bk internal structure, all 32 bits of data are transferred simultaneously on 32-lane connections. Similarly, parallel transmission is commonly used to transfer data from computer to printer. The printer is connected to the parallel port of the computer and a parallel cable that has many wires is used to connect the printer to the computer. It is a very fast data transmission mode.

Serial Transmission: In serial data transmission, bits of data flow in sequential order through a single communication line. Serial data & transmission is shown in the figure below. The flow of traffic on a one-lane residential street is an example of serial data transmission mode. Serial transmission is typically slower than parallel transmission because data is sent sequentially in a bit-by-bit fashion. Serial mouse uses serial transmission mode in computer.

Types of Data.

Numeric: Numeric data consists of digits from 0 to 9, + (positive) or –

(negative) signs and decimal points. It can be of integer type or real type data.

Text: A text consists of words,: sentences, paragraphs etc. 

Image: Image data consists of charts, graphs, pictures, and freehand drawings. Image data is also represented by bit patterns, but to represent image data, a different mechanism is used. The simplest method to represent an image is to divide the image into a matrix of pixels (picture element). A pixel represents the smallest dot of the image. The size of the pixel depends on the resolution of the image

Audio: Audio is a representation of sound. It is continuous and not discrete. The audio data is in the form of continuous signal. It is converted to digital form before entering the computer.

Video: Video consists of full-motion images that create actions and movements. It can be produced by a video camera.

What is a Local Area Network?     

A Local Area Network (LAN) is a network system in which computers are interconnected in a limited geographical area, such as a network of computers college computer laboratory, or network of computers in an office building, etc. LANs are designed to allow resources (such as printers and application programs, secondary storage, etc.) to be shared between personal computers or workstations. The size LAN is limited to a few kilometers (typically it is 1 km).

Advantages of LAN.     

The resources can be shared among different users. For example, many users on the network can use a single printer. Similarly, storage media and software located in the central server can be shared between all users on the networks.

  • LAN is not very expensive and small businesses, firms, and educational institutes can afford and easily design the LAN.
  • Users can share messages and communicate with each other through e-mails and chatting.
  • All the data is stored and updated on the central server through nodes. So it becomes very easy to take a backup of the database at regular intervals.
  • Multiple users can access the Internet using a single Internet connection. The Internet connection is established at the central sewer. In this way, all the users can access the Internet.
  • Data security can be implemented very easily because users are granted data access rights. The authorized users can connect to the server and can access specific portions of the data.
States the four disadvantages of LAN.   

If central server is infected by virus, then the important data stored on the server may be corrupted and the entire network may also be held.

  • All nodes depend on the central computer (or Hub), if any component of the server fails, then the entire network will stop working.
  • A trained and competent network manager is required to run the LAN, so a handsome salary has to be paid to him. Therefore, it becomes very expensive to run the LAN.
  • Mostly in a LAN, one or two printers are shared among several users. In this way, lengthy print queues are created, so the users have to wait for a long period to take print on the printer.
What is a Wide Area Network?

A Wide Area Network (WAN) is a network system that covers a large (wide) geographical area such as different cities of the country or different countries of the world. Most telephone companies are WANs.

A WAN that is wholly owned and used by a single company is often referred to as an enterprise network.

What is a Data Communication Protocol?  

Rules to send and receive data are called protocols. These rules are defined in the network software. Eg which is communicated, how it is communicated when it is communicated?

Functions of Communication Protocol.

Data Sequencing – The function of a protocol to divide the long message into smaller packets of fixed size that are to be transmitted for error free data transmission, called Data Sequencing.

Data Routing – The function of a protocol to find the most efficient path or route between the sender and the receiver before sending the data is called Data Routing.

Flow Control – The function of a protocol to control the rate of data transmission from the sender to the receiver is called Flow Control. It regulates the process of sending data between a fast sender and a slow receiver.

Error Control – The function of a protocol to detect and recover errors for successful data communication between the sender and the receiver is called Error Control. Successful data communication means that data is transmitted without any error.

What is a Metropolitan Area and Virtual Private Network?       

A Metropolitan Area Network (MAN) is a network system that covers the area of a single city. Usually, a MAN connects more than one LANS in a city or town and covers a smaller geographical area than a WAN

Advantages of the Internet.      

Sharing Information: You can share information with other people around the world. The scientists or researchers can interact with each other to share knowledge and to get guidance etc. Sharing information through the Internet is the very easy, cheap, and fast method.

Collection of Information: A lot of information of different types is stored on the web server on the Internet. It means that billions of websites contain different information in the form of text and pictures.

You can easily collect information on every topic of the world. For this purpose, special websites, called search engines are available on the Internet to search information on every topic of the world.

The most popular search engines are altavista.com, search.com, yahoo.com, ask.com, etc. Scientists, writers, engineers, and many other people use these search engines to collect the latest information for different purposes. Usually, the information on the Internet is free of cost. The information on the Internet is available 24 hours a day.

News: You can get the latest news of the world on the Internet. Most of the newspapers of the world are also available on the Internet.

They have their websites from where you can get the latest news about the events happening in the world. These websites are periodically updated or they are immediately updated with the latest news when any event happens around the world.

Searching Jobs: You can search for different types of jobs all over the world, Most of organizations/departments around the world, advertise their services and products via the Internet. Search engines are also used to search the jobs on the Internet. You can apply for the required job through the Internet.

Advertisement: Today, most of commercial organizations advertise their product through the Internet. It is a very cheap and efficient way for the advertising of products. The products can be presented in an attractive way to people around the world.

Communication: You can communicate with others through the Internet around the world. You can talk by watching to one another; you are talking with your friends in your drawing room. For this purpose, different services are provided on the Internet such as; Chatting, Video conferencing, E-mail, Internet telephony etc.

Entertainment: The Internet also provides different types of entertainment to people. You can play games with other people in any part of the world. Similarly, you can see movies, listen to music, etc. You can also make new friends on the Internet for enjoyment.

Online Education: The Internet provides the facility to get online education. Many websites of different universities provide lectures and tutorials on different subjects or topics. You can also download these lectures or tutorials into your own computer. You can listen to these lectures repeatedly and get a lot of knowledge. It is a very cheap and easy way to get an education.

Online Results: Today, most universities and education boards provide results on the Internet. The students can watch their results from any part of the country or world.

Online Airlines and Railway Schedules: Many Airline companies and Pakistan Railway provide their schedules of flights and trains respectively on the Internet.

Online Medical Advice: Many websites are also available on the Internet to get information about different diseases. You can consult a panel of online doctors to get advice about any medical problem. In addition, a lot of material is also available on the Internet for research in the medical field.

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