Two kinds of DVD: Single layer (left) and dual layer (right).
ADVD (which means Digital Versatile Disc or a Digital Video Disc) is an optical disc capable of storing up to 4.7 GB of data, more than six times what a CD can hold. DVDs are often used to store movies at better quality than a VHS. DVDs can also have interactive menus and bonus features such as deleted scenes and commentaries. Like CDs, DVDs are read with a laser.
The disc can have one or two sides, and one or two layers of data per side; the number of sides and layers determines how much it can hold. A 12 cm diameter disc may have one of the following storage capacities:
The capacity of a DVD-ROM can be visually determined by noting the number of data sides, and looking at the data side(s) of the disc. Double-layered sides are usually gold-colored, while single-layered sides are usually silver-colored, like a CD. One additional way to tell if a DVD contains one or two layers is to look at the center ring on the underside of the disc. If there are two barcodes, it is a dual layer disc. If there is one barcode, there is only one layer.
DVD Data Storing
BothCD and DVD discs have equal sizes (diameter, thickness etc.). However, the amount of information they can store is different. These discs are made of the same materials and have the same methods of production.
CDs and DVDs use the same way of keeping information. Both CDs and DVDs have pits and bumps on the data track (the data track represents a path which has certain information). The information is read by a laser.
A DVD disk has several layers, which are made of plastic. All layers have a thickness of 1.2 millimeters. An injection used on a polycarbonate plastic leads to the creation of microscopic bumps. Today’s production uses this type of plastic to create different things because it can resist very high and low temperatures.
When layers are made, the bumps appear. Many bumps form one continuous spiral that can include information.
After that a spray of a special reflective layer covers the bumps.
Aluminum is applied behind inner layers and semi-reflective gold covers the outer layers. This helps the laser to concentrate through the outer layers onto the inner ones. Then, after applying a protective liquid (lacquer) and pressing the layers, they are treated with infrared light.
LESSON ROUND-UP
– A computer system in contemporary usage refers to a desktop system including the computer along with any software and peripheral devices that are necessary to make the computer function.
– Hardware and software are the two basic parts of a computer system Hardware - any part of a computer system you can touch Software - a set of electronic instructions that tell a compute what to do.
– Computers are of various types as Analog Computers which are used to process continuous data such as flow, temperature, pressure, angular position or voltage and Digital Computers which are used to perform Arithmetic calculations and also make logical decision to reach a conclusion, depending on, the data they receive from the user. Hybrid Computers refers to various specifically designed computers with both digital and analog characteristics combining the advantages of analog and digital computers when working as a system. Hybrid computers are being used extensively in process control system where it is necessary to have a close representation with the physical world.
– Computers can be classified on the basis of size, generations, and functions.
– There are many news technologies being introduced in computers. Now computer has moved from office to home. Tablets, Laptop, Palmtop are some of the newer technologies computers which are used extensively by people.
– A computer collects processes, stores and outputs information Input Device are the peripherals which lets us to communicate with a computer. A keyboard, mouse, and joystick are input devices. Storage Devices are used to place information on a storage media. A floppy drive, recordable CD-ROM, tape drives and DVD-ROM are considered storage devices
– CPU is the abbreviation for central processing unit. Sometimes referred to simply as the central processor, but more commonly called processor, the CPU is the brains of the computer where most calculations take place. In terms of computing power, the CPU is the most important element of a computer system.
– Processor / CPU - Central Processing Unit is the main chip in a computer. The CPU processes instructions, manages the flow of information through a computer system. The CPU communicates with input, output and storage devices to perform tasks.
– Output device lets a computer communicate with us. These devices displays information on a screen, printed copies, or generate sound. Examples of output devices are printer, scanner, plotters, monitors etc.
– Byte refers to one character; a character can be a number, a letter or symbol. Consists of eight bits. Bit - The smallest unit of information a computer can process. Kilobyte (K)- One kilobyte = 1024 characters.
This is approximately equal to one page of double spaced text. Megabyte (MB) - One Megabyte = 1,048,576 character. This is approximately equal to one book. Gigabyte (GB) - One Gigabyte = 1,073,741,824 characters. This is approximately equal to a shelf of books in a library. Terabyte (TB) -One terabyte = 1,099,511,627,776 character. This is equal to an entire library of books.
– Hard Drive is the primary device that a computer uses to store information. RAM Temporarily stores information inside a computer. This information is lost when you turn off the computer.
– Motherboard/System board - The main circuit board of a computer. All electrical components plug into the mother board.
– Port – It is a connector at the back of a computer where you plug in an external device such as printer or modem. This allows instructions and data to flow between the computer and the device. Parallel Port - has 25 holes. This type of port is known as a female connector. A parallel port connects a printer or tape drive. Serial Port - has either 9 or 25 pins. This type of port is known as a male connector. A serial port connects a mouse or modem. USB Port - Universal Serial Bus - allows you connect up to 127 devices using on one port.
– MONITOR and VIDEO CARD A monitor and video card work together to display text and images on the screen. Video card - a circuit board that plugs into and expansion slot inside the computer. The video card translates instructions from the computer to a form the monitor can understand. Also called the video adaptor, graphics board or graphics card.
SELF-TEST QUESTIONS
(These are meant for re-capitulation only. Answers to these questions are not to be submitted for evaluation) 1. What do you mean by a computer system? Explain the basic functions of a computer system.
2. What are the difference types of computers? Explain the difference between Analog and Digital computers?
3. Classify the computers on the basis of generations 4. Classify the computers on the basis of size
5. What do you mean by Super computers? Explain the difference between Super computer and main frame computers.
6. What is the difference between a work station and person computers? Explain.
7. What do you mean by Central Processing unit (C.P.U)? Explain the functions of C.P.U in details.
8. Explain about four input devices of a computer.
9. Explain about four output devices of a computers
10. What are the storage devices being used in a computers?
11. What do you mean by “Cache Memory”? Explain its basic functions.
12. What do you mean by RAM and ROM? Explain the difference between RAM and ROM.
SHORT QUESTIONS AND MCQS 1. The TV type of screen is called a ______________.
2. Which of the following best characterizes the first generation of computing?
(a) Emphasis on marketing computers to business (b) Computers used for mainly scientific calculations.
(c) Speeds in microseconds (millionth/sec) (d) Software is an emphasis
3. Which of the following is not a printer?
(a) Laser (c) scanner
(b) Dot matrix (d) Ink-Jet
4. The component of the computer that would best be characterized as a traffic cop is
(a) Central processing unit (c) Motherboard
(b) Data Bus (d) RAM
5. The component of the computer that is responsible for temporary storage of information is known as
(a) Central processing unit (c) Motherboard
(b) Data Bus (d) RAM
6. What is the basic unit of composition of an image on a screen called?
(a) Resolution (c) Video Card
(b) Pixel (d) Bit
7. Which of the following has the least capability to computers?
(a) Floppy Disk (c) CD-WR
(b) Hard Disk (d) Zip Disk
8. All the following are input devices except:
(a) Keyboard (c) Mouse
(b) Voice Activated Devices (d) Printer
9. PC stands for ____________ _______________.
10. What was the first name of the two co-founders of Apple?
(a) Bill (c) Steve
(b) Paul (d) Heraldo
LESSON OUTLINE
– Computer Software: An Introduction, – System Software
– Application Software – Firmware
– Software Trends – Multi-Programming, – Multi-Processing, – Time Sharing, – Batch Processing
– On-Line and Real Time Processing – Systems Securities
– Lesson Round Up – Self Test Questions
LEARNING OBJECTIVES
Computers have become an important part of each of our’s life. Basically a computer system is a combination of two parts. Hardware and Software. Hardware constitutes the physical part of a computer which one can see but the software is something which is intangible in nature. It is the set of instruction which carries out the whole processing by a computer system.
In other words we may say that hardware is the body of a computer system while software is the soul of the computer. System. After going through this lesson, student would be able to – – Understand about software and its
classification
– Understand the functions of different types of software
– Understand the meaning of Multiprogramming and Multiprocessing – Understand about time sharing, batch
processing, online processing and real-time processing
– Understand about requirement of system security and different aspects relating to system security.
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