Monday, 29 November 2010
Logic gates
Tuesday, 9 November 2010
Hardware Devices
Input Devices
Mouse
The mouse uses the xy position indicator to track the movement of the mouse. It does this by beam a laser to the surface to follow the movement across the surface which is directly correspondant to the cursor on the screen.
Keyboard
The standard computer keyboard is used to enter text into a computer system. The electronic components in the keyboard continually scan the rows of keys to detect the pressing of a key or key combination. They identify which keyt/key combination has been pressed and send the key's scan code to the computer.
Graphics Tablet
The tablet picks up the information in the pens tip via sensors behind the screen or a cluster of lasers spread across the tablet in order to determine position and other information like pressure. Since the grid provides the power to the pen, no batteries are required.
Camera
Just like a conventional camera it has a series of lenses that focus light to create an image of a scene. But instead of focusing this light onto a piece of film, it focuses it onto a semiconductor device that records light electronically. A computer then breaks this electronic information down into digital data
Touch-sensitive Screen
A touchscreen is an electronic visual display that can detect the presence and location of a touch within the display area. The term generally refers to touching the display of the device with a finger or hand. Touchscreens can also sense other passive objects, such as a stylus.
Bar code Reader
A bar code reader, or bar code scanner, is an electronic device for reading barcodes printed on items such as cans, carboard and plastic packaging, and the covers of books or magazines. A bar code is a sequence of white and balck bars that encodes information such as a product indentifier. The product is usually printed in a human-readable from beneath bar code.
Smart Card Reader
A smart card, chip card, or integrated circuit card (ICC), is any pocket-sized card with embedded integrated circuits. The reader picks up the chip decodes the binary message and reads the content which usually is encripted for the user.
Magnetic Stripe Reader
A magnetic stripe reader reads the black or brown stripe on many cards such as; bank cards, id cards and discount cards etc. It does this by a electro magnet that reads data from the strip when it is slid down the reader, this information is usaually stored on a centeral database in the location.
Radio Frequency Identification Reader
Radio frequency idencification (RFID) users radio frequencies (RF) to tramsit data, a timming signal and energy between a reader and an RFID device. RFID devices do not need a physical eletrical contact to transfer data.
Optical Mark Reader
An optical mark reader optically senses marks placed in predefined positions on a form. The form is placed under a light source and the intensity of reflected light from each row of the form is measured and converted by photoelectric sensors into an electrical equivalent.
Optical Character Reader
All optical character recognition (OCR) systems use an optical scanner to input images of text then analyse the resulting digital images to recognise the characters. OCR systems are used to automate postal sorting.
Flatbed scanners
A flatbed scanner reflects light off of the object placed on top of the scanner and a mirror image is produced. A cover is used to block out any other light.
Fingerprint Scanner
An optical scanner works by shining a bright light over your fingerprint and taking what is effectively a digital photograph If you've ever photocopied your hand, you'll know exactly how this works. Instead of producing a dirty black photocopy, the image feeds into a computer scanner.
Iris/Retina Scanner
A retina scanner consists of a low-energy infared light source that is directed ionto the retina of the eye. An iris scanner uses a camera sensitive to infared light and placed no more than 3ft from the subject to capture an image of their iris and store it electroncially.
Output Devices
Cathode Ray Tube (CRT) Monitor
The CRT Monitor contains a tube of which is a vacum with a narrow neck and a rectangle base. The screen is coated on the inside with a phosphor that emits light when stuck by an electron beam. The retinal image from each phosphor dot persists in the human brain for about 0.05 seconds.
Liquid Crystal Display (LCD)
A liquid crystal display flat screen is a matrix of liquid crystal cells and each cell constitutes one pixel when the screen is used at full resolution. For colour displays, each pixel is divided into three or four subpixels with colours for additive mixing of red, green and blue.
Plasma Screen
Plasma screens are ideal for large displays. Each pixel is controlled by a miniature flourescent light. When the voltage is applied, the gas becomes plasma and releases UV light, which strikes phosphoros on the front of the screen to emit visible light.
Inkjet Printer
Non-impact printers transfer ink to paper using electrostatics or some either non-impact technique. Inkjet printer can print high-quality text, graphics an photographic images in colou. An inkjet printer produces coloured output by priniting a line of colour at a time. Printing a line of characters involves prinitng several lines of colour before the whole line of characters emerges.
Laser Printer
A laser printer prints a whole page at a time. It prints high quality text and graphics on plain paper. A page description language usally describe the page to be printed as lines. acrs and polygons. A processor in the laser printer generates a bitmap of the page in raster memory from the page description. A negative charge is applied to the photo sensitive drum at the heart of the laser printer. One or more laser beams are directed on the rotating drum's surface.
Impact (Dot Matrix) Printer
Impact printers are used in application that require multi-part stationery or printed through carbonised envelopes, prehaps to print payslips or credit card PINs sent by a bank to a customer. Impact printers use an inked ribbon to mark paper with an impression of a character. In a dot-matrix printer, the ribbon is struck hard by up to 24 metial pins that form the outline of the character.
Plotter Printer
A plotter is an output device that moves a pen across paper in a continuous movement so that a two-dimensoinal drawing can be made. The pen is lifted when not drawing on the paper and lowered to draw on the paper. For high-qulity work, special drawing paper is used to reduce in spreading or bleeding or the papers service.
Storage Media
Mouse
The mouse uses the xy position indicator to track the movement of the mouse. It does this by beam a laser to the surface to follow the movement across the surface which is directly correspondant to the cursor on the screen.
Keyboard
The standard computer keyboard is used to enter text into a computer system. The electronic components in the keyboard continually scan the rows of keys to detect the pressing of a key or key combination. They identify which keyt/key combination has been pressed and send the key's scan code to the computer.
Graphics Tablet
The tablet picks up the information in the pens tip via sensors behind the screen or a cluster of lasers spread across the tablet in order to determine position and other information like pressure. Since the grid provides the power to the pen, no batteries are required.
Camera
Just like a conventional camera it has a series of lenses that focus light to create an image of a scene. But instead of focusing this light onto a piece of film, it focuses it onto a semiconductor device that records light electronically. A computer then breaks this electronic information down into digital data
Touch-sensitive Screen
A touchscreen is an electronic visual display that can detect the presence and location of a touch within the display area. The term generally refers to touching the display of the device with a finger or hand. Touchscreens can also sense other passive objects, such as a stylus.
Bar code Reader
A bar code reader, or bar code scanner, is an electronic device for reading barcodes printed on items such as cans, carboard and plastic packaging, and the covers of books or magazines. A bar code is a sequence of white and balck bars that encodes information such as a product indentifier. The product is usually printed in a human-readable from beneath bar code.
Smart Card Reader
A smart card, chip card, or integrated circuit card (ICC), is any pocket-sized card with embedded integrated circuits. The reader picks up the chip decodes the binary message and reads the content which usually is encripted for the user.
Magnetic Stripe Reader
A magnetic stripe reader reads the black or brown stripe on many cards such as; bank cards, id cards and discount cards etc. It does this by a electro magnet that reads data from the strip when it is slid down the reader, this information is usaually stored on a centeral database in the location.
Radio Frequency Identification Reader
Radio frequency idencification (RFID) users radio frequencies (RF) to tramsit data, a timming signal and energy between a reader and an RFID device. RFID devices do not need a physical eletrical contact to transfer data.
Optical Mark Reader
An optical mark reader optically senses marks placed in predefined positions on a form. The form is placed under a light source and the intensity of reflected light from each row of the form is measured and converted by photoelectric sensors into an electrical equivalent.
Optical Character Reader
All optical character recognition (OCR) systems use an optical scanner to input images of text then analyse the resulting digital images to recognise the characters. OCR systems are used to automate postal sorting.
Flatbed scanners
A flatbed scanner reflects light off of the object placed on top of the scanner and a mirror image is produced. A cover is used to block out any other light.
Fingerprint Scanner
An optical scanner works by shining a bright light over your fingerprint and taking what is effectively a digital photograph If you've ever photocopied your hand, you'll know exactly how this works. Instead of producing a dirty black photocopy, the image feeds into a computer scanner.
Iris/Retina Scanner
A retina scanner consists of a low-energy infared light source that is directed ionto the retina of the eye. An iris scanner uses a camera sensitive to infared light and placed no more than 3ft from the subject to capture an image of their iris and store it electroncially.
Output Devices
Cathode Ray Tube (CRT) Monitor
The CRT Monitor contains a tube of which is a vacum with a narrow neck and a rectangle base. The screen is coated on the inside with a phosphor that emits light when stuck by an electron beam. The retinal image from each phosphor dot persists in the human brain for about 0.05 seconds.
Liquid Crystal Display (LCD)
A liquid crystal display flat screen is a matrix of liquid crystal cells and each cell constitutes one pixel when the screen is used at full resolution. For colour displays, each pixel is divided into three or four subpixels with colours for additive mixing of red, green and blue.
Plasma Screen
Plasma screens are ideal for large displays. Each pixel is controlled by a miniature flourescent light. When the voltage is applied, the gas becomes plasma and releases UV light, which strikes phosphoros on the front of the screen to emit visible light.
Inkjet Printer
Non-impact printers transfer ink to paper using electrostatics or some either non-impact technique. Inkjet printer can print high-quality text, graphics an photographic images in colou. An inkjet printer produces coloured output by priniting a line of colour at a time. Printing a line of characters involves prinitng several lines of colour before the whole line of characters emerges.
Laser Printer
A laser printer prints a whole page at a time. It prints high quality text and graphics on plain paper. A page description language usally describe the page to be printed as lines. acrs and polygons. A processor in the laser printer generates a bitmap of the page in raster memory from the page description. A negative charge is applied to the photo sensitive drum at the heart of the laser printer. One or more laser beams are directed on the rotating drum's surface.
Impact (Dot Matrix) Printer
Impact printers are used in application that require multi-part stationery or printed through carbonised envelopes, prehaps to print payslips or credit card PINs sent by a bank to a customer. Impact printers use an inked ribbon to mark paper with an impression of a character. In a dot-matrix printer, the ribbon is struck hard by up to 24 metial pins that form the outline of the character.
Plotter Printer
A plotter is an output device that moves a pen across paper in a continuous movement so that a two-dimensoinal drawing can be made. The pen is lifted when not drawing on the paper and lowered to draw on the paper. For high-qulity work, special drawing paper is used to reduce in spreading or bleeding or the papers service.
Storage Media
| Storage medium | Capacity | Transfer speed | Access time (ms) |
| Magnetic Hard Disk | 19.3 GB to 1.2 TB | 5 – 110 MB/s | Under 10 |
| Magnetic Floppy Disk | 737,280 to 1,474,560 bytes | 250 – 500 Kbits/s | 94 |
| Magnetic tape cartridge or cassette | 10-800 GB | 200 KB/s to 20 MB/s | Long |
| CD-ROM, CD-R, CD-RW | 600 – 700 MB | 153,600 to 7,372,800 B/s, 1x to 48x | 100 |
| DVD-ROM, DVD-R, DVD+RW, DVD-RAM | 2.8 – 17.1 GB | 1,385,000 to 22,160,000 B/s, 1x to 16x | 100 |
| Blu-ray | 25 – 50 GB | 36 – 288 Mbits/s, 1x to 8x | 110 |
| PDD | 25 – 50 GB | 10 MB/s | 100 |
| HD DVD | 15 – 51 GB | 36 Mbit/s | 500 |
| USB Flash Drive | 32 MB – 64 GB + (256GB) | 1-60 MB/s | 0.8 to 10 |
| Memory Card | 128MB to 64 GB + | 900 KB/s to 22.5 MB/s | 0.8 to 10 |
| Storage medium | Applications |
| Magnetic Hard Disk | Online storage of programs and data files |
| Magnetic Floppy Disk | Backing up and transferring small file, boot disk for an appropriate system |
| Magnetic tape cartridge or cassette | Backing up and archiving large volumes of data |
| CD-ROM, CD-R, CD-RW | Distributing software or videos, Transferring files, storing photos, backing up data, archiving data |
| DVD-ROM, DVD-R, DVD+RW, DVD-RAM | Transferring files, distributing software or videos, storing photos, backing-up and archiving data |
| Blu-ray | Distributing Videos |
| PDD | Backing up and archiving data |
| HD DVD | Recording high-density video |
| USB Flash Drive | Transferring files, running applications |
| Memory Card | Storing photos in a digital camera; storing music in audio devices; storing data in a mobile phone |
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