Hardware

Overview

Video from 0:00 until 1:10

https://www.youtube.com/watch?v=W6Sf8QiV_BU&list=PLCiOXwirraUA01kiMeInAiYvVnFhhMMqb&index=1 (0:00 - 1:10)

Hardware Definition

Hardware is a collective term for the physical parts of a computer system; this also includes peripheral devices, not just the internal components. Hardware is the platform on which software is run, and is more invariable than software. However, the configuration of the hardware in the system can be changed by adding new adapters or cards to improve the system's capabilities. Examples of hardware include motherboards, keyboards, video cards and mice.

Hardware can be simply defined as components of a computer system that can be touched and altered physically.

Input Output Devices

https://www.youtube.com/watch?v=ysyv-qyJPh4&index=124&list=PLCiOXwirraUDUYF_qDYcZV8Hce8dsE_Ho

You will need to cover the principles of operation for the following devices:

RFID

RFID or Radio Frequency Identification is where a small device emits a small radio wave with a specific ID on it so that it can be detected. These are most commonly used in shops in an effort to stop theft. RFID tags are attached to items that need tracking. An RFID reader is called an interrogator, and it uses two antennas to create an electromagnetic field. When the tag enters the electromagnetic field it is powered up and immediately transmits its data to the reader.

RFID tags can be Active, they include a battery to power the transmitter giving a better range and more uses. Alternatively they can be passive, the no battery is used and the transmitter is only powered when in the electromagnetic field.

Barcode Reader

A barcode reader reads a barcode and translates it into text that a computer can understand and decode. These are most commonly used in industry and shops to identify products quickly and easily.

Barcodes represent numbers 0 to 9 by giving each a unique combination of black and white bars contained within the same amount of horizontal space per digit. Barcode scanners read this information using a scanning head that shines an LED or laser light onto the barcode. The white areas of the barcode reflect the most light back to scanner, while black areas absorb the most and reflect the least. The reflected light is detected by a photoelectric cell in the scanner. As the scanner moves over the barcode, the cell generates a series of on-off pulses that represent the black and white stripes, which are then converted to zeroes or ones by an electronic circuit. The scanner is attached to a computer which uses the resulting binary value to identify the product from a database of barcodes and product numbers.

Laser Printer

Data is inputted into the printer and an electronic circuit figures out how to print this data. This activates the corona wire which produces a static charge to anything it touches. The corona wire positively charges the photoreceptor drum. The laser bounces off a mirror to produce the image; wherever it touches becomes negatively charged. Where the page should be white is positively charged and areas that are black are negatively charged. The toner is then painted across the image, the toner is positively charged so attracts to negatively charged areas of the page. A positively charged blank page is moved near the drum so the toner transfers from the drum to the page. The fuser unit then heats the page so the toner fuses permanently.

Digital Camera

A digital camera is a camera which encodes digital images and stores them for later reproduction. The aperture at the front of the camera opens to let light through the lens. A light detector captures the incoming light rays and converts them into electrical signals. An image sensor - a CMOS image sensor or a Charge-Coupled Device (CCD) - chip breaks up the image into pixels, measuring the colour and brightness of each one. The image itself is a large string of numbers describing each pixel.

Secondary Storage Devices

https://www.youtube.com/watch?v=LM2Vx4Rt_cs&index=125&list=PLCiOXwirraUDUYF_qDYcZV8Hce8dsE_Ho

You will need to cover the principles of operation for the following devices:

Optical Disk

An optical disk is a flat circular disk which encodes binary data in the form of pits (0's) and lands (1's) on a reflective surface. The data is created using a stamping machine and can be accessed using a laser on the underside of the disk (the reflective side) to reflect the light to form the 1's and 0's created by the lands and pits, as lands will reflect this light back to the photocell, which is registered as a 1 and pits will reflect this light elsewhere, and are counted as 0s.

Some disks have a dye recording layer between the reflective layer and a protective layer. The pits and lands are burned into dye rather than the disk itself to make the disk recordable (Write Once). Re-writable disks use a special dye which can be burned as normal, but when heated to a higher temperature the dye will clear.

The data is stored in a single track, it tends to start from the inside and spirals to the outside edge.

Hard Disk

A hard disk is made of a circular disk coated in a magnetic material called a platter, which spins at up to 10000 rpm. Each area of the platter can be independently magnetized or demagnetized by a read/write head to store a 1 or a 0. The read/write head is a tiny magnet that moves across the platter as it spins. One platter has two read/write heads - one to read the top of the disk, and one to read the bottom side. Data is written to the disk in concentric, circular paths called tracks. Each track is broken into sectors, and part of the hard drive stores a map of which sectors contain data and which are free.

Solid State Drive

A solid state drive has no moving parts - instead, data is saved to a pool of flash memory with floating gate transistors. Unlike the transistors used in RAM, these can retain their charge state even when the computer is turned off, making flash memory non-volatile. Since SSDs have no moving parts, they can read and write at far faster speeds than magnetic hard drives or optical disks.

Comparing Storage Media

https://www.youtube.com/watch?v=dthiLXaq9Us&list=PLCiOXwirraUDUYF_qDYcZV8Hce8dsE_Ho&index=126