Monitor and Plotter

THE MONITOR

A monitor or display (sometimes called a visual display unit) is an electronic visual display for computers. An electronic visual display is a piece of electrical equipment which performs as output device for presentation of images transmitted electronically, for visual reception, without producing a permanent record. Common applications for electronic visual displays used to be television sets or computer monitors.

Pixel: Computers can use pixels to display an image as shown in Figure (1).  

·         In digital imaging, a pixel, or pel (picture element) is a single point in image.

·         It is the smallest unit of picture that can be represented or controlled.

This example shows an image with a portion greatly enlarged, in which the individual pixels are rendered as little squares and can easily be seen

Figure (1)

Resolution of computer monitors: The display resolution is determined by the video card of the computer. The number of pixels or picture elements on the screen determines the resolution or clarity of the picture that monitors achieve. High resolution monitors have resolution of 2000×2000 pixels. The old fashioned International Business Machines (IBM) PC, for example, with a Color Graphic Adaptor (CGA) can output image with a resolution of 640×200 pixels. This was adequate for character-based displays but for graphics it was inferior to the displays of more advanced machines such as the Apple Macintosh.

In the mid-1980s IBM introduced the Enhanced Graphic Adaptor (EGA), which offered a high resolution. This gave a much better clarity, though it was still not as good as the Macintosh.

Then in 1987, IBM brought out the Video Graphic Array (VGA) on its Personal System/2 or PS/2 (IBM’s third generation of PC) range of microcomputers with a resolution of 640 by 480.

In 1990 IBM brought out its Extended Graphics Array(XGA) with a resolution of 1024 by 768 pixels and support for 65000 colors. Super VGA with the same resolution became the standard.

Cathode Ray Tubes:  Most computer monitors are based on Cathode Ray Tubes (CRT) similar to those used in TV sets. The unique function of a CRT is to convert electronic signals to a visual display. Figure (2) illustrate the basic operation of a CRT. All CRT's have four main elements:

1.      an electron gun,

2.      Focusing System

3.      a deflection system

4.      A screen.

Figure (2)

The electron gun provides an electron beam, which passes through focusing and deflection systems that direct the beam toward specified points on the phosphor coated screen.

Electrons emitted by the cathode (electron gun) are attracted to the focusing anode. This is the reason that they travel through the small hole in the grid.  

Deflection:  Something is necessary to produce the picture. That something is called deflection. The deflection system positions the electron beam on the screen, and the screen displays a small spot of light at the point where the electron beam strikes it.

Deflection of the electric beam is done with electric field. The beam passes between two pairs of metal plates: one pair vertical, the other pair horizontal. A voltage difference is applied to each pair of plates according to the amount that the beam is to be deflected in each direction. As the electron beam passes between each pair of plates, it is bent toward the plates with the higher positive voltage.

The CRT screen: The inside of the large end of a CRT is coated with a fluorescent material that gives off light when struck by electrons. This coating is necessary because the electron beam itself is invisible. The material used to convert the electrons' energy into visible light is a PHOSPHOR.

Since the light emitted by the phosphor fades very rapidly, some method is needed for maintaining the screen picture. One way to keep the phosphor glowing is to redraw the picture repeatedly by quickly directing the electron beam back over the same points. This type of display is called refresh CRT. It redraws 30 to 60 times in a second in order to avoid flicker. If the redraw is below 25 times per second then the picture flickers.

Persistence of phosphor: How long the phosphor continues to emit light after the electron beam is removed. Lower persistence phosphor requires higher refresh rate to maintain a picture on the screen without flicker. A phosphor with low persistence is useful for animation, while high persistence phosphor is better suited for displaying static pictures.

In color screen, there are three guns, one for each color Red, Green and Blue (RGB). The combination of these three gives the full color spectrum.

Old monochrome models display text and graphics as either green on a black background or white on a black background. The monochrome monitors are gradually declining as most of the models developed these days uses many colors.

FLAT SCREEN: Flat screen are slowly replacing the CRT monitors as they are bulky. These were introduced for use on battery operated portable computers, as these consume very little power. Liquid Crystal Display (LCD) use flat screen. In an LCD, the image is formed by liquid crystals. These are long rod-like molecules through which solid can flow like a liquid. Each pixel on the screen consists of a microscopic electrode positioned below these mole cules.

Color CDs require very fast liquid crystals. In passive matrix display; there are three screens, colored red, green and blue which are placed on top of each other. Below the three screens are the thousands of pixels electrodes which generate light. The pixel in each screen acts as filters for this light. If a pixel is to be red, the green and blue filters above it are turned on, blocking out those colors but the red filter is off, allowing the red light to pass on. By turning the filters on and off in other combinations, other colors can be obtained.

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PLOTTER

A plotter is an output device that uses colour ink pens to draw maps, charts, diagrams and other drawings on the paper. Plotters have been used in automotive and aircraft design, topological surveys, architectural layouts, civil engineering drawings and other similar complex drafting jobs. A plotter is composed of a pen, a moveable carriage, a drum, and a holder for chart paper. Both the pen and the paper can move up and down and back and forth. This permit very detailed drawings.

Plotters work on the principle of a human hand holding a pen and moving it on the paper. Plotters are normally very slow output devices because of excessive mechanical movement required during plotting but the output is of better quality.

Plotters are of two types:

1.      Flatbed Plotter                         

2.      Drum Plotter

1.    Flatbed Plotter:

It is less expensive. It plots on paper that is spread and fixed over a rectangular flatbed as shown in figure (A). Pens of different colours are mounted in the pen holding mechanism that moves on the surface in two orthogonal directions. The pen can be raised and lowered on to the paper during the drawing operations. The microprocessor in the plotter selects the desired pen and controls its movement under the control of the computer.

Figure (A)

2.    DRUM Plotter

Drum plotter are normally used with mainframe and minicomputer systems. The paper on which the design has to be made is placed over a drum that rotates back and forth to produce vertical motion. The pen is mounted on the carriage, which moves across the width of the paper. The vertical and horizontal movement of the paper create the required design under the control of the computer. Pen having ink of different colors can be used to produce output in multicolored.

Figure (B)

Video Camera

VIDEO CAMERA

Video cameras are multipurpose devices, being able to capture images of any type. Modern video cameras have many designs and uses:-

1.         Professional video cameras (often called a television camera), such as those used in television and sometimes film production; these may be studio-based or mobile Figure 1. Early studio television camera -- Grey box on right is the lens as illustrated in Figure 2.

                  Figure 1                              Figure 2

2.       Camcorders(videocamera recorder), which combine a camera and a VCR or other recording device in one unit; these are mobile, and are widely used for television production, home movies, electronic news gathering (including citizen journalism), and similar applications. Some digital ones are Pocket video cameras.

Figure 3: Camcorders

Pocket Video camera: A pocket video camera is a tape less camcorder that is small enough to be carried in one's pocket (Figure 4). Most pocket video cameras resemble mobile phones in shape and size, unlike traditional cameras. A tape less camcorder is a camcorder that does not use videotape for recording video. Tapeless camcorders record video as digital files onto random access media such as optical discs, hard disk drives and solid-state flash memory.

Figure 4: Pocket video camera

3.       Closed-circuit television (CCTV) cameras, generally used for security, surveillance, and/or monitoring purposes (Figure 5). Such cameras are designed to be small, easily hidden, and able to operate unattended; those used in industrial or scientific settings are often meant for use in environments that are normally inaccessible or uncomfortable for humans, and are therefore hardened for such hostile environments (e.g. radiation, high heat, or toxic chemical exposure).

Figure 5: Surveillance cameras on a corner

4.       Web Cam is a video camera which feeds its images in real time to a computer or computer network, often via USB, Ethernet or Wi-Fi.  Their most popular use is the establishment of video links, permitting computers to act as videophones or videoconference stations.

Figure 6: Web Cam

5.       Digital Cameras which convert the signal directly to a digital output; such cameras are often small, even smaller than CCTV security camera. A digital camera (or digicam) is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography. Digital cameras can do things film cameras cannot: displaying images on a screen immediately after they are recorded, storing thousands of images on a single small memory device, and deleting images to free storage space. The majority, including most compact cameras, can record moving video with sound as well as still photograph.

Figure 7: Digital Camera

5.       Special Systems like those used for scientific research, e.g. on board a satellite or a space probe, or in artificial intelligence and robotics research. Such cameras are often tuned for non-visible radiation for Infrared photography (for night vision and heat sensing) or X-ray (for medical and video astronomy use  

Character Recognition Device & Microphone

CHARACTER RECOGNITION DEVICE

Character-recognition device enables the user to input text and numerical data by handwriting it in capital letters on the pressure-sensitive surface using a specials pen. An invisible grid of fine wires below the surface detects the shape of the letters, converting them to electrical signals which the computer interprets using special software. Although this device is a genuine replacement for the keyboard, it has never become as popular as keyboard.This powerful tool allows businesses to convert paper documents into electronic files

Optical Character Recognition: It is abbreviated to OCR, is the mechanical or electronic translation of scanned images of handwritten, typewritten or printed text into machine-encoded text. It is widely used to convert books and documents into electronic files, to computerize a record-keeping system in an office.

Optical Character Recognition (OCR) refers to a computer's ability to recognize printed letters, numerals, or symbols (optical characters) as discrete entities rather than as simply an image containing lines, curves, and shading.

In place of a character that they cannot recognize, they will substitute a special symbol. These symbols can be automatically picked out and replaced later on with the aid of spell-checking software.

How does OCR operate/process? When a printed page of text is scanned, the scanner delivers an image of the text to OCR software stored in the attached computer. The software then attempts to identify each letter of each word in the image in order to covert it to an editable text document or to process the information in whatever format is needed as illustrated in the Figure 1, Figure 2 and Figure 3 (Digital Camera is also used in place of scanner).

Figure 1: OCR Operation

  

Figure 2: OCR Operation

 Figure 3: OCR

OCR is increasingly used in conjunction with bar coding and other forms of automatic identification systems. Bar coding is an automatic identification technology that allows data to be collected rapidly and accurately with minimal human effort. Bar codes provide a simple method of encoding text information that can be easily read by electronic scanners integrated with computer systems. It is useful in almost any field that requires unique identification and tracking of a large number of items.

Some OCR programs are designed to recognize correct grammar and common spellings so they automatically highlight words that they have copied, but that they also find questionable.

Original Problems with OCR: What usually confused the OCR software were imperfections on the printed page like stains, extraneous marks, fading, and blurring. Letters had to be crisply printed. Unusual fonts were impossible for the OCR to understand and duplicate. Strikeovers also confused OCR programs. Even slightly blurry, shiny type from thermal fax paper could throw the software into fits.

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THE MICROPHONE

The microphone converts audio signals (sound) to electrical waves and these can be converted by electronic circuitry in the computer to digital form.

HOW DO THEY WORK? A microphone is an example of a transducer, a device that changes information from one form to another. Since the sound information exists as patterns of air pressure; the microphone changes this information into patterns of electric current. The term transducer is applied to any device which converts a mechanical or other measurable phenomenon into an electrical one or vice versa. Examples of transducers are: ·         Microphones  ·         Loudspeakers

A microphone wants to take varying pressure waves in the air and convert them into varying electrical signals. Microphones are transducers which detect sound signals and produce an electrical image of the sound, i.e., they produce a voltage or a current which is proportional to the sound signal. The most common microphones for musical use are dynamic, ribbon, or condenser microphones.

Different types of microphone have different ways of converting energy but they all share one thing in common: The diaphragm. This is a thin piece of material (such as paper, plastic or aluminium) which vibrates when it is struck by sound waves. In a typical hand-held mic like the one shown in Figure (1), the diaphragm is located in the head of the microphone.

Figure (1): Hand-held Mic

When the diaphragm vibrates, it causes other components in the microphone to vibrate. These vibrations are converted into an electrical current which becomes the audio signal. Figure (2) illustrates the USB desktop microphone.

Figure (2): USB Desktop Microphone

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Computer Memory and its Terminologies

WHAT IS COMPUTER MEMORY?

In computing, memory refers to the physical devices used to store programs (sequences of instructions) or data on a temporary or permanent basis for use in a computer.

Memory is what enables your PC to operate. The computer's CPU (central processing unit) is the computer's brain, but a brain is useless without memory.

One of the major advantages that digital systems have over analog systems is the ability to easily store large quantities of digital information and data for short or long period of time. In a digital computer the internal main memory stores instructions that tell the computer what to do so that the computer will do its job with a minimum amount of human intervention.  Magnetic tape and magnetic disk are popular storage devices that are much less expensive than internal memory devices.

MEMORY TERMINOLOGY

1.       Memory cell:

Computer memory is made up of memory cells, where each memory cell contains exactly one number. This is a device or electrical circuit used to store a single bit (0 or 1).  The number contained in a memory cell can be changed over time. When a new number is stored into a memory cell, the old number contained in the memory cell is lost forever. At any time, the computer may examine into a memory cell to read the current contents of the memory cell. A typical computer has millions of memory cells, and every memory cell has a name. The unique number that names a memory cell is called its `address.' No two memory cells have the same address. The address of a memory cell never changes over time. Every memory cell has two numbers -- its address (which never changes) and its current contents (which changes over time.)

2.       Memory Word:

This is a group of bits in a memory that represents information or data of some type. Word size in modern computers typically ranges from 4 to 64 bits, depending on the size of the computer (depend upon the microprocessor). The most popular word size for modern computers is 16, 32, or 64-bits.

3.       Byte:

Computer memory is measured in terms of bytes. Byte is a special term used for 8-bits word i.e. 1 byte= 8 bits. In modern digital computers, the word size is usually a multiple of 8-bits such as 2 bytes or 4 bytes. Byte is a unit of storage capable of holding a single character. A character can be a number, letter or symbol.

The larger units are kilobyte, megabyte and giga byte. The relationship between these units is shown below:

1 byte= 8 bits

I kilobyte=1024 bytes

1 megabyte=1024 kilobytes=1048576 bytes

1 gigabyte=1024 megabytes = 1048576 kilobytes

4.       Memory capacity:

The amount of information a computer can store in memory. This is the way of specifying how many bits can be stored in a memory device. Suppose that we have a memory device which can store 4096 20 bits words. This represents a total capacity of 81,920 bits. We could also represent this memory capacity as 4096×20. When expressed this way, the first number 4096 is the number of words and the second number 20 is the number of bits per word (word size).

5.       Address:

The code that identifies where a piece of information is stored is known as address. This is a number that identifies the location of a word in memory. Each word stored in a memory device or system has a unique address. Addresses are always specified as a binary number, although octal, hexadecimal, and decimal numbers are often used.

Note: Kindly consult the text book at page-21 for further reading of Address and check out the Figure.

6.       Read Operation:

The operation through which the binary word stored in a specified memory location (address) is sensed. For example, if we want to read ‘word 4’ of the memory, we have to perform a read operation on address 100. Read operation is often called a fetch operation, since the word is being fetched from the memory.

7.       Write Operation:

This is the operation whereby a new word is placed into a particular memory location. It is also referred to as a store operation. Whenever a new record is written into a memory location, it replaces the word that was previously stored there.  The old word is lost in the process of writing the new word into this memory location.

8.       Access Operation

This is a measure of a memory device’s operating speed. It is the amount of time required to perform a read operation. It is the time between the memory receiving a read command signal and the data becoming available at the memory output.

9.       Cycle time

It is another measure of a memory device’s speed.  It is the amount of time required for the memory to perform to perform a read or write operation and then return to its original state ready for the next operation. Cycle time is normally longer than access time.

10.   Random Access Memory (RAM)

A type of computer memory that provides direct access to any single location is RAM. Random access memory or RAM most commonly refers to computer chips that temporarily store dynamic data to enhance computer performance.

Random access memory is volatile memory, meaning it loses its contents once power is cut.  This is different from non-volatile memory such as hard disks and flash memory, which do not require a power source to retain data.  The access time is the same for any address in memory because it provides random access to any memory location.

 11.   Sequential Access memory (SAM)

In computing, sequential access memory (SAM) is a class of data storage devices that read their data in sequence. This is in contrast to random access memory (RAM) where data can be accessed in any order. Sequential access devices are usually a form of magnetic memory.

The access time is not constant but varies depending on the address location. A particular stored word is found by sequencing through all address locations until the desired address is reached. This produces access times, which are much longer than those of random access memories. Example of Sequential access memory devices includes magnetic tapes.

12.   Read/Write Memory (RWM)

It is any memory that can be read from or written into with equal ease. Read-write memory is a type of computer memory that may be relatively easily written to as well as read from (unlike ROM or "Read-Only Memory").

13.   Read Only memory (ROM)

A ROM can be written into (Programmed) only once and this operation is performed at the factory. Thereafter, information can only be read from the memory. Other types of ROM are actually Read Mostly Memories (RMM) which can be written into more than once but the write operation is more complicated than the read operation. Therefore, the write operation is not performed is not performed very often.

14.   Static Memory Devices

The Semiconductor memory devices in which the stored data will remain permanently stored as long as power is supplied, without the need for periodically rewriting the data into memory are called Static memory devices. It is type of RAM that is quicker than dynamic RAM and does not need to be refreshed. Because it is more expensive and holds less data than dynamic RAM.

15.   Dynamic Memory Devices

It is type of RAM. These are the Semiconductor memory devices in which the stored data will remain not permanently stored even with power supplied, unless the data is periodically rewritten into memory. This operation is called a refresh operation.

WHAT IS INFORMATION TECHNOLOGY (I.T) ?

REPRESENTATION OF INFORMATION TECHNOLOGY IN A COMPUTER

I.T REVOLUTION

•  Information Technology (IT) is the use of modern technology to help in managing information i.e. storage, processing, analysis and communication/distribution of information.
• The tools we use to perform calculations, to store and manipulate text, and to communicate is the Information Technology. Some of these 20^th century tools include: the adding machine, calculator for performing calculations, the typewriter and word processor for processing text, and the telephone, radio, and television for communicating.
•  All types of equipment and programs which are used in the processing of information are called Information Technology.

Information Technology is not limited solely to computers though. With technologies quickly developing in the field of cell phones, PDAs and other handheld devices, the field of IT is quickly moving from computer-focused areas to other forms of mobile technology. A development in information technology is any improvement to the mechanism used to store, manipulate, distribute or create information.

EFFECTS OF INFORMATION TECHNOLOGY ON OUR LIVES:

Information Technology is playing a vital role on our lives. The general effects of information technology are as follows:

1.      Increased Reliance on Communication

People now use communication technology widely in their homes with fax machine, portable telephone, tele-text, satellite TV and use of the internet.

2.      Electronic Office

The new developments in information technology have made possible the electronic office. This is an office where most information such as documents, diagrams, finance and correspondence is handled electronically. It is stored digitally in computers rather than papers in filing cabinet. Spreadsheets and word processing software all provide a commercial benefit to the business.

3.      Handling Information

Information handling is very easy and fast with computers e.g. searching data, sorting it into order and analyzing it using database and other packages.

4.      Producing Models of Real Situations

Using spreadsheets, simulation programs and expert systems to form models. This allows a situation to be investigated.

5.      New Jobs Created through information Technology

A very large industry has grown up to produce and support information technology. This employs a large number of people.

6.      Information Technology Influenced The Way Governments Operate

The developments in information technology have helped governments to improve their “service” to their citizens. Advances in Database technology have enabled the governments to collect and monitor statistical information that they can use to fight against fraud, manage the economy in a more informed way.

Information Technology has also had a major impact on the defense capabilities of governments. Advances in weapons technology and weapons design have increased the effectiveness of various governments’ armed forces.

7.      Information Technology Influenced the Interactions Between Individuals

Individuals then have the ability to interact with other individuals through such developments as e-mail, chat-rooms and the Usenet. Internet technologies have enabled people with disabilities such as those who are blind or visually weaken physical disabilities or others to be able to enjoy access to sources of information and ways of communicating they may not have had the opportunity to have used before.

REPRESENTATION OF INFORMATION TECHNOLOGY IN A COMPUTER:Information can be represented in a computer in four different forms:

1.   Data: A data is a collection of facts, such as values or measurements. These facts are used to produce meaningful information. We process the data to produce information.
A data may be a name, a price, a quantity, a code number, an address etc. Data can exist in a variety of forms -- as numbers or text on pieces of paper, as bits and bytes stored in electronic memory, or as facts stored in a person's mind.

2.  Text: Text presents the information written as phrases and sentences. Although text is more longer than basic item of data but it is much more meaningful.

3.  Image: Image presents the information in pictorial form. This includes charts, graphs, pictures and drawings. Information in this form is more comprehensive than an item of data and more meaningful.

4.  Voice: Voice presents the information in spoken phrases and sentences. Like text, it is much more meaningful than an item of data.

THE IT REVOLUTION

Modern electronics is based upon the microprocessor, one form of microchip (A chip is also called an integrated circuit. Generally it is a small, thin piece of silicon onto which the transistors making up the microprocessor have been etched), which consists of miniature logic circuits engraved onto the surface of silicon chip. These tiny circuits replaced the glass valves used in the earliest computers of the 1940s and 1950s.

“Glass valve”

“Microprocessor”

The early computers processed information in the form of data. Modern computers are more powerful and can handle information in other forms including graphics and speech. However, they work on the same principles as the early models.

The main difference between the computers of 30 years ago and the microchip of today lies in the fact that the latter are very small, cheap, reliable, and powerful.

Ever since the first chips were made in the early 1970s their power has increased every year while their cost has decreased. It is this fact that has caused the information revolution.

MICROCOMPUTER OR PERSONAL COMPUTER

MICROPROCESSOR

Microcomputer or Personal Computer: A computer that uses a microprocessor as its central processing unit is known as microcomputer or personal computer. The first microprocessor was the Intel 4004, introduced in 1971.

Microprocessor:

Ø  A microprocessor controls the entire operation of a microcomputer. Thus, it is the brain of the computer. It is an information processing device.

Ø  A microprocessor, sometimes called a logic chip, is a computer processor on a microchip. It responds to and processes the basic instructions that drive a computer.

Ø  A microprocessor is designed to perform arithmetic and logic operations. Typical microprocessor operations include adding, subtracting, comparing two numbers and fetching numbers from one area to another.

Ø  A microprocessor is an “engine” that goes into motion when you turn your computer on. When your computer is turned on, the microprocessor gets the first instruction from the basis input/output system (BIOS) that comes with the computer as part of its memory. After that, either the BIOS or the operating system that BIOS loads into computer memory or an application program is “driving” the microprocessor, giving it instruction to perform.

Ø  Microprocessors are now built-in not just in to computers, but also into a wide range of other products from cameras to washing machines and cars. Microprocessor is used as a control mechanism in many of these products.