A-level Computing 2009/CIE/Theory Fundamentals/Hardware
The physical parts of a computer system that you can see and touch such as the keyboard,mouse and mouse are called hardware.There are four main categories of computer hardware:
- Input devices: used to enter data into the computer
- Processing devices: manipulate the data
- Storage device: store data and programs
- Output devices: show results of the process
An input device is hardware component that allows you to enter the data or instruction into the computer. There are many manual/automatic input devices. Most widelu used input devices are:
- Point devices
- 2d/3d scanners
keyboard Keyboard is the most commonly used input devices. The basic mechanical keyboard relies on springed keys being pressed down to complete an electrical circuit. This circuit then transmits a binary signal to the computer to represent the key pressed.
scanner Here are the steps that a scanner goes through when it scans a document: The document is placed on the glass plate and the cover is closed. The inside of the cover in most scanners is flat white, although a few are black. The cover provides a uniform background that the scanner software can use as a reference point for determining the size of the document being scanned. Most flatbed scanners allow the cover to be removed for scanning a bulky object, such as a page in a thick book. A lamp is used to illuminate the document. The lamp in newer scanners is either a cold cathode fluorescent lamp (CCFL) or a xenon lamp, while older scanners may have a standard fluorescent lamp. The entire mechanism (mirrors, lens, filter and CCD array) make up the scan head. The scan head is moved slowly across the document by a belt that is attached to a stepper motor. The scan head is attached to a stabilizer bar to ensure that there is no wobble or deviation in the pass. Pass means that the scan head has completed a single complete scan of the document. The image of the document is reflected by an angled mirror to another mirror. In some scanners, there are only two mirrors while others use a three mirror approach. Each mirror is slightly curved to focus the image it reflects onto a smaller surface. The last mirror reflects the image onto a lens. The lens focuses the image through a filter on the CCD array. The filter and lens arrangement vary based on the scanner. Some scanners use a three pass scanning method. Each pass uses a different color filter (red, green or blue) between the lens and CCD array. After the three passes are completed, the scanner software assembles the three filtered images into a single full-color image.
finger print technology Fingerprint recognition or fingerprint authentication refers to the automated method of verifying a match between two human fingerprints. Fingerprints are one of many forms of biometrics used to identify individuals and verify their identity. Retina scanner Retina scanner is used to record the pattern of blood vessels at the back of someone eyes.