IT (Information Technology)
IT is a technology that merges computing with high-speed communication links carrying data.
Computer
Definition: Computer is an electronic device used for manipulation and representation of data/ storing the data.
Definition: Computer is derived from the word compute which means to calculate. Computer is considered as calculating device that performs action at very high speed.
Note: Language is the way of communication.
What’s the language of computer?
Machine language is the language of computer and nowadays also known as binary language.
Machine language: Is an electronic circuit and it has only two states (on-off)
machine language
The native language of the computer. In order for a program to run, it must be presented to the computer as binary-coded machine instructions that are specific to that CPU model or family. Although programmers are sometimes able to modify machine language in order to fix a running program, they do not create it. Machine language is created by programs called "assemblers," "compilers" and "interpreters," which convert the lines of programming code a human writes into the machine language the computer understands.
Binary: is an Italian word and it is derived from binaries (double) and that’s (0-1).
(1) represents (on)
(0) represents (off)
Data: The collection of raw facts & figures is called data.
Information: The arranged and processed form of data which can give us a meaningful idea is called information.
Binary Numbers
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Binary Digit
Example:
*Floppy Disk=1.44 MB
* CD (Compact Disk) = 750 MB
Define a bit: A bit is the smallest unit of information that is recognized by a microcomputer. It is similar to a light bulb in that it can exist only in two states—it is either on or it is off.
Define a byte.
A byte is a group of eight bits. To represent one character of information requires one byte.
Development in Computers
The world's first electronic digital computer was developed by Army Ordnance to compute World War II ballistic firing tables.
The weight of that is 30 ton in (1961). At the first time Charles Babbage made the computer.
By Martin H. Weik, 1961
ENIAC contained 1500 relays and about 18000 tubes. Its energy consumption was up to 150 kW. The weight of ENIAC was about 30 tons and it covered an area of 140 square meters. It was able to make 5000 additions or subtractions per second. That was 1000 times faster than MARK 1.
MARK1
Calculator MARK1 developed in 1944 by Howard H. Aiken.
Types of Computer
1. Micro Controllers: are also called embedded computers, they’re tiny, specialized processor. Used in Kitchen appliances, like microwave oven, automobiles, cars, etc.
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RANGE: Embedded systems contain microprocessors pre-programmed to perform a dedicated task required by the device they control. APPLICATION: Examples are dedicated word-processing machines, chips in washing machines, laser printers and hand held calculators. PRICE: Prices depend on the application. |
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A microcontroller is an integrated chip that is often part of an embedded system. The microcontroller includes a CPU, RAM, ROM, I/O ports, and timers like a standard computer, but because they are designed to execute only a single specific task to control a single system, they are much smaller and simplified so that they can include all the functions required on a single chip.
A microcontroller differs from a microprocessor, which is a general-purpose chip that is used to create a multi-function computer or device and requires multiple chips to handle various tasks. A microcontroller is meant to be more self-contained and independent, and functions as a tiny, dedicated computer.
The great advantage of microcontrollers, as opposed to using larger microprocessors, is that the parts-count and design costs of the item being controlled can be kept to a minimum. They are typically designed using CMOS (complementary metal oxide semiconductor) technology, an efficient fabrication technique that uses less power and is more immune to power spikes than other techniques.
There are also multiple architectures used, but the predominant architecture is CISC (Complex Instruction Set Computer), which allows the microcontroller to contain multiple control instructions that can be executed with a single macro instruction. Some use a RISC (Reduced Instruction Set Computer) architecture, which implements fewer instructions, but delivers greater simplicity and lower power consumption.
Early controllers were typically built from logic components and were usually quite large. Later, microprocessors were used, and controllers were able to fit onto a circuit board. Microcontrollers now place all of the needed components onto a single chip. Because they control a single function, some complex devices contain multiple microprocessors.
Microcontrollers have become common in many areas, and can be found in home appliances, computer equipment, and instrumentation. They are often used in automobiles, and have many industrial uses as well, and have become a central part of industrial robotics. Because they are usually used to control a single process and execute simple instructions, microcontrollers do not require significant processing power.
The automotive market has been a major driver of microcontrollers, many of which have been developed for automotive applications. Because automotive microcontrollers have to withstand harsh environmental conditions, they must be highly reliable and durable. Nonetheless, automotive microcontrollers, like their counterparts, are very inexpensive and are able to deliver powerful features that would otherwise be impossible, or too costly to implement
2. Micro computers: are small computers that fit on desk on portable. Portable: Movable.
PC - The personal computer (PC) defines a computer designed for general use by a single person. While a Mac is a PC, most people relate the term with systems that run the Windows operating system. PCs were first known as microcomputers because they were a complete computer but built on a smaller scale than the huge systems in use by most businesses.
Desktop - A PC that is not designed for portability. The expectation with desktop systems are that you will set the computer up in a permanent location. Most desktops offer more power, storage and versatility for less cost than their portable brethren.
Laptop - Also called notebooks, laptops are portable computers that integrate the display, keyboard, a pointing device or trackball, processor, memory and hard drive all in a battery-operated package slightly larger than an average hardcover book.
Palmtop - More commonly known as Personal Digital Assistants (PDAs), palmtops are tightly integrated computers that often use flash memory instead of a hard drive for storage. These computers usually do not have keyboards but rely on touchscreen technology for user input. Palmtops are typically smaller than a paperback novel, very lightweight with a reasonable battery life. A slightly larger and heavier version of the palmtop is the handheld computer.
Workstation - A desktop computer that has a more powerful processor, additional memory and enhanced capabilities for performing a special group of task, such as 3D Graphics or game development.
Wearable – The latest trend in computing is wearable computers. Essentially, common computer applications ( e-mail, database, multimedia, calendar/scheduler) are integrated into watches, cell phones, visors and even clothing!
Mini Computers: are machines midway in cost and capability between Micro computers and Main frame computer, or Another term rarely used anymore, minicomputers fall in between microcomputers (PCs) and mainframes (enterprise servers). Minicomputers are normally referred to as mid-range servers now.
Server - A computer that has been optimized to provide services to other computers over a network. Servers usually have powerful processors, lots of memory and large hard drives.
Example: They’re used by medium size companies, and are used fro designing and accounting purpose.
Main Frame Computers: The large computers called Main frame computers. Are the oldest categories of computers is called Main frame computer they occupy special air conditional rooms and capable of great processing speeds, and storage area. They’re about size of Jeep. Price range from $50,000 to $5 million and they need special programmers and professional to operate and also they’re used by Large Companies like Banks and Airlines.
OR
Mainframe - In the early days of computing, mainframes were huge computers that could fill an entire room or even a whole floor! As the size of computers has diminished while the power has increased, the term mainframe has fallen out of use in favor of enterprise server. You'll still hear the term used, particularly in large companies to describe the huge machines processing millions of transactions every day.
APPLICATION: Mainframe computers generally require special attention and are kept in a controlled atmosphere. They are multi-tasking and generally used in areas where large databases are maintained e.g. government departments and the airline industry.
5. Super Computers
Super computer are high capacity, fastest, device ever invented. The computer which is known as fastest of its era is called super computers. Supercomputer - This type of computer usually costs hundreds of thousands or even millions of dollars. Although some supercomputers are single computer systems, most are comprised of multiple high performance computers working in parallel as a single system and they’re typically priced from $225000 to over $30 million. Also they’re used for special proposes.
(a)Oil Exploration
(b)Weather Forecasting
© Space explorations like NASA used super computer.
Example of Super Computer
Basic Operations of computers
Usually computers operate in four categories.
1. Input Operations
2. Processing Operations
3. Output Operations
4. Storage Operations
Input Operations: In input operations data is entered and converted to a form that can be processed by computer.
Or
Input - The mean for capturing data is input devices.
Example: Keyboard, Mouse or etc.
ASCII: American Standard Code for Information Interchange.
Processing Operation: In processing operation the data is manipulated or processed, that transform it into information.
Transform: Change
Example: 4+5=9
1000101+1000111=1001010
Output Operations: In output operation obtained from the data is produced in form that’s useable for the user/people.
Example: Like Monitor, Printer, Speaker, Plotters.
Storage Operations: In the storage operations data and information are permanently stored in computer process able format.
Permanently: Primary
Example: Disk is the example of material used for storage. Kind of disk: floppy disks, compact disks, magnetic disk.
Storage Operations
Components of Computer System
Computer is equal to Hardware plus Software. Computer=Hardware+ Software
Hardware
All the physical components or parts of the computer is known as hardware or anything which can be touched is known as computer hardware or Hardware consist of all the machinery and equipment in computer system.
Hardware=Internal devices+ Peripheral devices.
Internal devices: Are those devices which are fitted inside the computer system, like Mother board, Sound Card, RAM, Hard disk, Video card or etc.
Peripheral Devices: Is any piece of hardware that’s externally connected to the computer.
*Like keyboard, mouse, cameras, external modem, printer, scanner or etc.
Computer Hardware Categories
Hardware devices are often categorized according to the operation they perform.
Input, Output, Processing, and Storage/memory.
*Communication it self have hardware.
Input hardware: Consist of devices that allow people to put data into the computer in a form that computer can use.
Input - Information and programs are entered into the computer through Input devices such as the keyboard, disks, or through other computers via network connections or modems connected to the Internet. The input device also retrieves information off disks.
Input hardware can be categorized into three types.
1. Keyboard 2.Pointing devices 3.Source data entry devices
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ENTER or RETURN - Moves the cursor down one line and to the left margin. Enter also process commands such as choosing an option in a dialog (message) boxes and submitting a form.
BKSP or BACKSPACE - Deletes the character to the left of cursor and all hightlighted text.
SPACE BAR - Moves the cursor one space at a time to the right
SHIFT KEY - Use the shift keys to type capital letters and to type the upper character on keys with two characters on them
CAPS LOCK - Locks the keyboard so it types capital letters (a light goes on when caps lock is on)
TAB - Moves the cursor five spaces to the right (number of spaces are usually adjustable). Tab moves to the next field in a form or table (Shift-Tab for previous field).
ESC or ESCAPE - Cancels a menu or dialog box
ARROW KEYS - Moves the cursor around document without changing text
FUNCTION KEYS or F KEYS - Access commands by themselves or in combination with the three command keys; CTRL, SHIFT, and ALT
Command keys normally do nothing on their own but work in combination with other keys. Each piece of software uses the command keys differently though there is a move to standardize some functions. The Control key or Ctrl is often used to access commands. The Alternative key or Alt is often used to access menus. The Shift key is used to type CAPITAL LETTERS. As well the command keys are all used to move through documents and edit text faster and easier. As well many computers have Special keys design specifically for the particular computer. Apple computers have the Apple keys and Macs have Command keys. Many keyboards now have a Windows key specifically for Windows 9x and newer systems. Many older computers also have special keys used for a variety of different functions.
Some Notebook or Laptop keys are left out because of space limitations and they usually have a Special function key which allows other keys to double for the missing ones.
Electrical singles: Are binary numbers
*May look like type writer keyboard to which some special keys have been added.
Control the position of the curser or pointer on the screen or monitor. Like mouse, light pens, trackball, digital tablet.
(a)Light pens usually used in cricket.
(b)Trackball and Digital tablet. In Laptop.
Refers to the many forms of data entry devices, those aren’t keyboard or pointing devices.
Scanner: uses laser beams and reflected light to translate images of text, drawings, photo and other data into digital format.
Bar Code Reader: Is a vertical zebra stripped marks into must of the manufacturer products.
Bar Code
MICR: Magnetic Ink Character Reader. This is also known as Mark-recognition or character recognition devices.
An example of one of the uses of magnetic ink in automatic character recognition. Because of the difficulties in forging magnetic-ink characters, and the speed with which they can be read by computer systems, MICR is used extensively in banking.
(Image © Research Machines plc)
In computing, a technique that enables special characters printed in magnetic ink to be read and input rapidly to a computer. MICR is used extensively in banking because magnetic-ink characters are difficult to forge and are therefore ideal for marking and identifying cheques.
A computer can read numbers and letters printed with ink containing magnetic material.
A cheque detailing the MICR number
MICR is used by banks to process cheques. The account details at the bottom of the cheque can be accurately read in this manner since MICR is not affected by dirt.
*It’s used to read the strange looking numbers.
OMR: Optical Mark Recognition: uses a device that read pencil mark, and converts them into computer useable form.
Short for optical mark recognition, the technology of electronically extracting intended data from marked fields, such as checkboxes and fill-infields, on printed forms. OMR technology scans a printed form and reads predefined positions and records where marks are made on the form. This technology is useful for applications in which large numbers of hand-filled forms need to be processed quickly and with great accuracy, such as surveys, reply cards, questionnaires and ballots. A common OMR application is the use of “bubble sheets” for multiple-choice tests used by schools. The student indicates the answer on the test by filling in the corresponding bubble, and the form is fed through an optical mark reader (also abbreviated as OMR, a device that scans the document and reads the data from the marked fields. The error rate for OMR technology is less than 1%.
The Optical Mark Reader (OMR) can read information in the form of numbers or letters and put it into the computer.
The marks have to be precisely located as in multiple choice test papers.
A sample multiple choice answer paper
Magnetic reader:
This input device reads a magnetic strip on a card. Handy for security reasons, it provides quick identification of the card's owner.
A Credit card showing the magnetic strip
Smart Cards
This method is used to run bank cash points or to provide quick identification of people entering buildings.
This input device stores data in a microprocessor embedded in the card. This allows information, which can be updated, to be stored on the card.
A store card showing the square microprocessor chip
This method is used in store cards which accumulate points for the purchaser, and to store phone numbers for cellular phones.
Voice Data Entry
This system accepts the spoken word as input data or commands.
Human speech is very complex, involving emphasis and facial expressions, so complete voice recognition will not be developed for some time.
A microphone used for data input
Sound Capture
However, simple commands from one user can be used to control machines.
In this way a paralysed person can operate a wheelchair or control heating and
With the addition of a sound card in one of the expansion slots of your computer you can "record" voice or music.
The sound card digitises the information into a form that the computer can understand.
Video Capture
With a video capture board in one of your computer's expansion slots you can capture video (photographic) images through a video camera.
The video capture board digitises the image.
A video capture card
Joystick
The joystick is a rotary lever. Similar to an aircraft's control stick, it enables you to move within the screen's environment, and is widely used in the computer games industry.
A joystick
Digitising Tablet
A Digitising Tablet is a pointing device that facilitates the accurate input of drawings and designs.
A digitising tablet with pen
A drawing can be placed directly on the tablet, and the user traces outlines or inputs coordinate positions with a hand-held stylus.
Touch Sensitive Screen
A Touch Sensitive Screen is a pointing device that enables the user to interact with the computer by touching the screen.
There are three forms of touchscreen: pressure-sensitive, capacitive surface and light beam.
Light Pen
A Light Pen is a pointing device shaped like a pen and is connected to a VDU.
The tip of the light pen contains a light-sensitive element which, when placed against the screen, detects the light from the screen enabling the computer to identify the location of the pen on the screen.
Light pens have the advantage of 'drawing' directly onto the screen, but this can become uncomfortable, and they are not as accurate as digitising tablets.
Space Mouse
The Space mouse is different from a normal mouse as it has an X axis, a Y axis and a Z axis. It can be used for developing and moving around 3-D environments.
A space mouse
Digital Stills Camera
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The digital images can then be downloaded from the camera to a computer where they can be displayed, manipulated or printed. |
A digital stills camera |
Output Hardware
Output hardware consist of devices that translate information processed by the computer into a form that human can understand.
Output: Output Devices displays information on the screen (monitor) or the printer and sends information to other computers. They also display messages about what errors may have occurred and brings up message or dialog box asking for more information to be input. The output device also saves information on the disk for future use.
They’re two principle kind of output hardware
Softcopy: such as display screen.
Hardcopy: such as printer, plotter or etc.
Softcopy hardware/Display screen
Are also called monitors, CRT or simply screen.
Visual Display Units (VDU)
These are devices that show programming instructions and data as they’re being input and information after it’s processed.
Also is known as VDT (Video Display Terminal) VDT is technical with keyboard.
Size of screen is measured diagonally. Monitor standard size 14” to 17 inches.
They’re two types of display screens.
(a) CRT (Cathode Rays Tube) = Monitor.
(b) Flat-Panel Display.
CRT
CRT Monitor stands for Cathode Rays Tube.
It’s most common types of display screen. The same technology is found in Television set and flight information monitor in Airport.
They consist of one or more guns (which fires stream of electron) known as electron gun.
Images are represented on the screen by individual dots called pixel.
Pixel for picture element is the smallest unit on the screen that can be turn on or off or made different shades.
Inside the front of CRT screen is coated with the chemical called phosphors.
Working
Stream of bit defining the image is sent from the Computer (from CPU) to CRT electron gun where the bits converted to electron.
Those electrons repeatedly scan the screen from top to bottom, dot by dot, line by line in fraction of seconds.
When been of electron hits the phosphor it light up selected pixel to generate an image on the screen.
Resolution: the number of pixels on the screen is called pixel resolution.
Dot pitch: The distance between pixels on the monitor is called Dot pitch. It’s mentioned in millimeter (mm) 2.8mm.
Refresh rate: The number of time in one second that the electron been redrawing the entire image is called Refresh rate.
*It’s measured in Hz (Hertz) =cycles/second
Mono chrome Monitor
Only provide one colour.
Colour:
Background colour: Black
Fore ground colour: White or green
The base text mode in Dos in 80 characters by 25 characters
Text Mode
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25 Rows
The Color Graphic Adapter, introduced in 1981, was IBM’s first color graphics card, and the first color computer display standard for the IBM PC., and Developed by IBM (International Business Machine), PC.
CGA Monitor, only provide two colours. CGA supported by 640x200
Horizontals 640x pixels
EGA
Enhanced Graphics Adapter. High resolution IBM graphics standard capable of displaying 640 x 350 pixels in 16 colors out of a palette of 64 colors.
VGA
VGA stands for Video Graphics Adapter. VGA supported 640x480. Provide 256 colour.
A standard of video adapter developed by IBM that can support a display with a resolution up to 640 x 480 pixels in 256 colors
XGA
XGA: (1990) stands for Extended Graphics Array. XGA supported 1024x768 pixels. Provide 65000 colour.
SVGA
SVGA stands for Super Video Graphics Adapter. SVGA supported 1024x768 pixels. Provide 16 million colour.
Flat Panel Monitor
Different between CRT, and Flat Panel Monitor
Flat Panel Monitor is replacing CRT because of their huge size and space they occupy, because of consume of more power (electric) their huge size weight/ they weren’t potable.
Comparatively Flat Panel is much thinner, weightless, and consumes less power, they’re better for portable computers.
Flat Panel LCD, (Liquid Crystal Display) Monitor.
LCD monitors use Flat Panel screen. In LCD image is made by liquid crystal, which is liquid substance between two plates of glass. This is activated in different ways.
Hard Copy Output device
There are two kinds of hard copy device
(a) Printers
(b) Plotters
Printers: is an output device that prints characters, symbols, and graphics on paper or other hard copy medium.
This device is capable to give reports and al other type of information in written form.
Printer
You can print out information that is in the computer onto paper. By printing you create what is known as a 'hard copy'.
There are different kinds of printers which vary in their speed and print quality.
The two main types of printer are impact and non-impact.
(a) Impact printer
(b) Non-impact printer
(a) Impact printer: in impact printer form character, image by striking a mechanism such as print hummer or wheel against an ink ribbon, leaving an image on the paper.
Example: Like Dot Matrix Printer, and Line Printer.
Dot Matrix Printer: they’re commonly used printer, the data in dotted form. Their quality is judged by the number of pins present in their “writing head”. Commonly available print heads are with 9 pins, 18 pins, and 24 pins.24 pins is the best quality.
Dot matrix printers have a horizontally moving head with a vertical line of pins mounted inside. An inked ribbon is located between the head and the paper and as the head moves the pins strike the ribbon to form each character as a series of dots. The best quality printers have heads with 24 pins and low quality ones have 9 pins (although by making two passes and shifting the head half a pin pitch between them they can effectively act as as a 18 pin head). As these printers can produce small dots anywhere on the paper most support graphics and have software fonts. Dot matrix printers are quite noisy but can be cheap. They are mostly for low to medium quality, low volume personal use. They are obsolete now.
Line Printer: they’re fast printer with 300 to 3000 lines per minute. Rather then a single character at a time they print whole lines of character at once. These printers are used for heavy duty/large printings.
Line printers have a spinning horizontal drum that stretches the full width of the paper which is separated from it by an inked ribbon. The drum is made up of 132 thin cylinders each having a complete set of characters. Behind the paper is a row of 132 hammers that strike the paper at the right moment to select the required character from the corresponding cylinder. In this way it is able to print a complete line at a time. Line printers are used for high volume low quality output and are very noisy. They are obsolete now.
On a daisy-wheel printer the complete set of characters is held on a removable wheel which consists of a central collar radiating out from which are a set of spokes, each ending in a single character. The wheel spins round to align the required character with a single hammer. The hammer and wheel assembly move across the paper striking it through an inked ribbon. These printers can produce high quality output but are limited to the range of characters on the wheel. Changing wheels is simple, this provides alternative fonts, but is no substitute if a wide range of fonts is required. They are quiet noisy and are used for low volume office work. They are obsolete now.
(b) Non-impact printers: from character and images without making physical contact between printing mechanism and paper.
There are two kind of Non-impact printer.
(1) Laser printer (Laser jet)
(2) Ink Printer
(1) Laser printer: it’s similar to photo copy machine, they provide best quality printings.
A type of printer that utilizes a laser beam to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. This is also the way copy machines work.
In a laser printer, paper is given an electro-static charge by passing it over a charged drum and then a laser scans it discharging all clear areas. Next the paper is passed over a tray of powdered ink (toner) which is attracted to the charged areas. Finally the ink is bonded to the paper by heat or pressure. Laser printers are quiet and are used for high quality low or high volume work. We have a number in the department including PS9 (a Postscript printer near 615) and PS4 (a double sided Postscript printer outside room 663).
In this case laser light writes directly onto film inside a camera to make very high quality full colour output. Again the process is expensive and the volume low. OUCS have a camera copy service that takes Postscript format files.
(2) Ink Jet printer: spray small electrically charged drops of ink from nozzles through holes. At very high speed into paper. They can print in colour. They’re quieter. They’re less expensive, and speed ranges from 1 to 4 pages/ minute.
Ink jet printers have a movable head that can spray fine drops of ink directly on to the paper. Some have multiple heads carrying coloured inks with the best ones providing a wide range of colours. As the paper and the head never come into contact they are very quiet. However they are also rather slow. They are generally cheaper than laser printers and are suitable for all types of high quality low volume work. We have a few in the department including one colour Postscript one CPS2.
Thermal printer
Characters are formed by heated elements being placed in contact with special heat sensitive paper forming darkened dots when the elements reach a critical temperature.
A fax machine uses a thermal printer
Thermal printer paper tends to darken over time due to exposure to sunlight and heat. The standard of print produced is poor.
Thermal printers are widely used in battery powered equipment such as portable calculators.
(c) Plotters: is special output device design to produce high quality graphics drawing and maps in different colour. There are two main types of Plotter.
The last type of hardcopy output device isn’t really a printer at all. Printers make images one line at a time and more from top to bottom during the printing process plotters, on the other hand, draw the image as we would, with a pen. Once shape at a time. Plotters are most often used with CAD software to provide blueprints or technical diagrams. It would be quite expensive to make a printer that can print on paper as wide these drawings require. Because a plotter uses a pen (or several pens in a holder) on a cable carrier, it’s easy (and relatively expensive) to make a very wide plotter.
A plotter is a vector graphics printing device that connects to a computer.
Plotters print their output by moving a pen across the surface of a piece of paper. This means that plotters are restricted to line art, rather than raster graphics as with other printers. They can draw complex line art, including text, but do so very slowly because of the mechanical movement of the pens. (Plotters are incapable of creating a solid region of colour; but can hatch an area by drawing a number of close, regular lines.)
Another difference between plotters and printers is that a printer is aimed primarily at printing text. This makes it fairly easy to control, simply sending the text to the printer is usually enough to generate a page of output. This is not the case of the line art on a plotter, where a number of printer control languages were created to send the more detailed information like "draw a line from here to here". The most popular of these is likely HPGL.
Early plotters (e.g. the Calcomp 565 of 1959) worked by placing the paper over a roller which moved the paper back and forth for X motion, while the pen moved back and forth on a single arm for Y motion. Another approach (e.g. Computervision's Interact I) involved attaching ball-point pens to drafting pantographs and driving the machines with motors controlled by the computer. This had the disadvantage of being somewhat slow to move, as well as requiring floor space equal to the size of the paper, but could double as a digitizer. A later change was the addition of an electrically-controlled clamp to hold the pens, which allowed them to be changed and thus create multi-colored output.
For a time in the 1980s smaller "home-use" plotters became popular for experimentation in computer graphics. But their low speed meant they were not useful for general printing purposes, and you would need another conventional printer for those jobs. With the widespread availability of high-resolution inkjet and laser printers, plotters have all but disappeared.
Plotters were also used in the Create-A-Card kiosks that were available for a while in the greeting card area of supermarkets.
Plotters are used primarily in technical drawing and CAD applications, where they have the advantage of working on very large paper sizes while maintaining high resolution. Another use has been found by replacing the pen with a cutter, and in this form plotters can be found in many garment and sign shops.
A niche application of plotters is in creating tactile images for visually handicapped people on special thermal cell paper.
Note that in many of today's environments, plotters in the traditional sense have been supplanted with (and, in many cases, obsoleted by) large-format inkjet printers. Such printers are often informally known as plotters, even though they are not by the definition of this article.
(1) Drum Plotters
(2) Flat Bed Plotters
(1) Drum Plotters: paper lies over drum which rotates back and forth. Suspended pen holder moves horizontal for drawing.
(2) Flat Bed Plotters: is designed so that paper lies flat on a table like surface the size of bed determines the maximum size of sheet of paper. Standard bed size in A4”, under computer control between one and four colours pens move across the paper.
Robots
Robots are able to perform a variety of tasks as a result of executing instructions contained within a program.
We are still a long way from the science fiction robots and androids portrayed by the film industry.
A robot arm
Robots in a business sense mean automated machines designed to perform mundane operations which require accuracy, such as assembling cars.
They are seldom manufactured to resemble the human form.
Processing Unit/Hardware/System Unit
Processing: The CPU or central processing unit is sometimes called the Control Unit and directs the operation of the input and output devices. The Coprocessor or the Arithmetic-Logic Unit does arithmetic and comparisons. The memory or RAM temporarily stores information (files and programs) while you are using or working on them. The BIOS or basic input/output system controls the dialogue between the various devices.
Processing Unit is most important and powerful part of computer system. It’s known as heart of computer system. Processing Unit allows various part of computer system to work together processing Unit in is further divided into two part.
(A) CPU (Central Processing Unit)
(B) Memory
(A) CPU: is the brain of computer system. It processes the data and sends the data/ result to the output devices. Some functions of CPU are:
(a) ALU (Arithmetic and Logical Unit).
(b) CU (control Unit).
(c) Registers.
CPU (Central Processing Unit)
The brain of any computer is the central processing unit (CPU). This components does all of the calculations and performs 90 percent of all the functions of a computer.
ALU: It perform the arithmetic operations, such as +, *, /, - or etc. It also performs logical operations such as comparing one number with another number.
CU (Control Unit): The control unit controls and coordinate the activities of all other computer unit, it main task include controlling the input unit and output unit, operation of all, and transferring data to and from computer memory. It also ensures that data is accurately moved from one area to another.
Register: are special but small memory unit which hold very small amount of data on temporary basics and pass it to the relevant unit. Number of register charges from computer to computer... However some register are common to all computers like a accumulator register. Data biffer registers.
Memory: Also known as main memory”, “primary storage”,
.
Memory: Also known as main memory”, “primary storage”,
RAM (Random Access Memory)
It’s the place where data and program are stored for immediate processing, so that they accessible directly to CPU.
Address part: contains unique address of memory location.
Content part: contains actual data.
RAM capacity is important because it determines how much data can be processed at once.
Common RAM capacities are 16 MB,
Secondary Storage Media/ hardware/ Permanent Storage Devices
Secondary storage is permanent storage. It’s not placed on mother board.
Definition: Secondary storage consists of devices that store data and programs permanently on disk or tape.
In many cases the information that has been processed is stored in machine-readable format so that it may be accessed at a later time by a computer. This data is stored in binary form in 'bits'.
This practice requires the use of storage devices.
Main storage media/ devices are.
(1) Diskette (Floppy disk).
(2) Hard disk.
(3) Magnetic tape.
(4) CD
Diskette: a floppy disk is removable, round, and flexible disk. Diskette is contained in plastic case to prevent the disk surface from being touched. The most common size is 3 ½ inches of diameter. To use diskette you need a disk drive in your computer.
Disk drive: is a device that holds and spin the diskette inside its case. It “reads” data from and “write” data to the disk. Capacity of floppy drive is 1.44 MB.
A floppy disk is a thin magnetic-coated disk contained in a flexible or semi-rigid protective jacket.
Data is stored in tracks and sectors.
A 3.5" floppy disk
The floppy disks are usually 3.5" in size. However, older floppy disks may be in use; these would be 5.25" in size.
Double sided high density 3.5" disks can hold 1.44 Mb of data.
Once data is stored on a floppy disk it can be 'write protected' by clicking a tab on the disk. This prevents any new data being stored or any old data being erased.
Hard disk: is normally fixed in system unit. Hard disk provides faster access to files then floppy disk. Capacity of hard disk is much larger then floppy disk.
Hard disk platter is a flat, round, rigid disk made of aluminum or glass coated with magnetic oxide.
Hard disk is one or more platters stacked on each other. Hard disk platters are found in different numbers between 1 to 50 plates. These plates are spin by central shaft. These platters are rotates at the speed 2400 RPM (revolution per minute). Information is stored on both sides of the platter except the upper surface of top plate and lower surface of the bottom plate, which are not used. Capacities of hard disk varies from 20MB to 98 GB, Like floppy disk, hard disk provide random access of files and data.
The hard disk is a direct-access storage medium with a rigid magnetic disk.
The data is stored as magnetised spots arranged in concentric circles (tracks) on the disk.
Each track is divided into sectors.
The number of tracks and sectors on a disk is known as its 'format'.
Hard disk showing internal mechanisms
High data rates demand that the disk rotates at a high speed (about 3,600 rpm). As the disk rotates read/write heads move to the correct track.
The disk is sealed and lubricated and the head hovers on a cushion of air just above the disk to avoid damage. These are therefore called floating heads.
The storage capacity of a hard disk can be Gigabytes (Gb), i.e. thousands of Megabytes (1000Mb), of information.
Magnetic tapes: are similar to video cassettes, magnetic is sequential memory. The access time of magnetic tape is much slower then floppy or hard disk.
The tape is plastic material usually ½ inch wide that’s coated with special material called metal di oxide. Magnetic tape is usually 50 to 2400 feet long. It’s similar to the tape used on the tape recorder or video recorder. Data on the tape can be erased and erased infinitely.
Erased: Delete
A recording medium consisting of a thin tape with a coating of a fine magnetic material, used for recording analogue or digital data. Data is stored in frames across the width of the tape. The frames are grouped into blocks or records which are separated from other blocks by gaps.
Magnetic tape is a serial access medium, similar to an audio cassette, and so data (like the songs on a music tape) cannot be quickly located.
A JAZTM drive with cartridge -
one of the many types of magnetic storage devices available
However large amounts of information can be stored within magnetic tape. This characteristic has prompted its use in the regular backing up of hard disks.
CD ROM: Stands for Compact Disk Read Only Memory.
Surface is coated with plastic material making the data permanent and unchangeable. CD ROM is also called optical disk, and data is read by laser light. Capacity of CD ROM is about 700 MB, because you can only retrieve data from CD ROM, but can’t save any new data on it, CD is called Read Only Memory. CD that allows new data to be stored as well as to erase whenever required is called Re Writeable CD.
Optical disk
An optical disk is impressed with a series of spiral pits in a flat surface.
A master disk is burnt by high-intensity laser beams in bit-patterns from which subsequent copies are formed which can be read optically by laser.
The optical disk is a random access storage medium; information can be easily read from any point on the disk. A standard CD-ROM can store up to 650Mb of data, with 14,500 tracks per inch (tpi).
CD-ROM stands for Compact Disk - Read Only Memory. It is now possible to have CD-ROMs where extra tracks of information can be written onto them by the user. These are called read/writable CD-ROMs and these are becoming a popular and cheap method for storage.
Punched Cards & Paper Tape
These are media which were popular in the past but their use required large storage space and was time-consuming.
With the development of hard disks and other storage devices their use has practically disappeared.
A strip of paper tape
Computer Software
Software or programs consist of instruction that tell the computer to perform a specific task. Software is written in special codes by programmer.
Software: is the term to describe any kind of computer programs.
Computer program: tell the computer hardware how to perform specific task. Computer program contains special instructions.
Example: 5+10=15
There are two major types of software.
(1) Application software (2) System software
Application software: is software that has been developed to solve a particular problem. Users directly interact with the software to perform a specific task.
Application software interacts with hardware through system software.
Win98: is system software.
Microsoft Word, Excel, or etc called application software.
There are two types of application software.
(1) Custom build software. (2) Package software/ shrink wrapped software.
Custom build software: is software designed for particular customer/ client. This is the kind of software that you would hire a computer programmer or software creator to develop for you. It’s build for specific clients to perform specific task.
Example: of package software are word processing programs, spread sheet programs, graphical software.
Spread sheet programs are used for accounting purpose, like Ms Excel, etc.
Application software can be used for.
Scientific, Engineering, Graphics purpose.
Example: Auto cad, Corel draw, Mathematic.
Entertainment software: such as Game, or etc.
Educational software: such as dictionaries, electronic, encyclopedia.
System Software
Directly interact with the hardware and controls the usage of hardware. It also enables application software to run, thus system software is required to run Application Software.
There are three basic types of system software.
Services of Operating System
Boot: Refers to the process of loading and operating system into the computer main memory until you turn the computer off.
Providing User Interface: Is the user controllable part of operating system that allow you to communicate or interact with the computer
Types of User Interface
a. Command Driven Interface b. Graphical User Interface
a. Command Driven Interface: In this interface user type the command and text format. Example of Command Driven Interface is Dos (Disk Operating System) and UNIX.
b. Graphical User Interface: It uses Graphics, Images to choose commands. Another feature of GUI is the use of Windows. Windows divide the display screen into rectangular section.
Example of GUI is windows (95, 98, 2003, XP), UNIX, Windows NT.
Managing computer resources: Operating system is the manager of resources and when resources are requested by different users at the same time then operating system locates these resources to many users and programs in efficient manner.
Managing Files: Files are located in many places on your hard disk and other storage device. Operating system allows you to find them and it also manages file commands such as Copy, Delete, Rename and etc.
Generating error massages: Whenever there is an error in the computer system like (file Missing, Resources missing), operating system is responsible to inform the user with the error generator.
Types of Utility Programs
Back up utilities: Utility programs that duplicates the contents of hard disk into a removable storage such as Hard disk, floppy disk etc.
Antivirus Utility: Software utilities that scan hard disk, floppy disk and other to detect viruses, and some antivirus also destroy viruses.
Virus: Virus is a hidden programming instruction within system or application software that copy themselves and causes user to lose data, files or even shutdown the entire computer.
Data Recovery Utilities: It’s used to “Undelete” file or data that has been accidentally deleted.
Example: Recycle Bin and Undo.
Data Compression Utilities: Removes redundant elements, gaps and unnecessary data form computer file, so less space is required to store or transmit data.
Example: WinZip 98
There are three types of language translator:
Is language translator that converts each high level language statement into machine language and execute it immediately statement by statement or line by line.
Example: Example of high level languages using interpreter is BASIC and SQL Language.
BASIC (Beginners all purpose symbolic instructions codes)
SQL (Structure Query Language)
