Chapter 7 Computer Artitecture

The disk is continuously spinning and data is read/ written as the correct sector passes under read/ write head

The disks are coated with a thin magnetic material changes in the direction of magnetism represent 0s and 1s

The disk is divided into tracks and sectors (tracks are concentric circles, sectors are blocks)

data is stored as a series of bumps/ pits within the track

A protective layer is put over the surface to prevent corruption

A laser reads the pits and lands which then interprets an electrical signal

It uses NAND flash memory and floating gate transistors which are used to trap and store charge Data must be written/ read in pages and erased in blocks

Permanent memory not connected to the processor, used to store data when the computer is turned off.

An infered light is shone at a bar code The light is reflected back Black/ white bands on the bar code reflect difference amounts of light (black less and white more) Light sensor measures the amount of reflected light. This light is convereted into an electrical signal. Electrical signal analyed to determine the vlaue encoded in bar code.

Cheap, quick to read and can be read at different angles

Limited amount of data can be stored

Read emits electromagnetic waves The RFID tag is energised by the waves The tag sends back the data signal via radio waves The reader receives the radio signal

Can be read without physical contact

Multiple RFID cards together can interfere with signal, thieves can interfere with your card without contact, more expensive to produce than bar codes

The shutter opens and lets light in through the lens, the light is focused onto a sensor usually a charge coupled device CCD the sensors are made up of millions of transistors, each stores the data for a pixel as the light hits the sensor the amount of charge is recorded for each pixel as binary If it is a colour camera then the camera can use three different sensors for (R, G and B)

You can see the images before developing them

THe quality of traditional photos is better than digital photos

A rotating drum inside the printer is coated in a chemical which holds and electrical charge The laser is reflected onto the drum via a rotating mirror The laser neutralises the electric charge on the drum where the image should be black Toner is given a positive charge and the drum picks up this toner Drum is rolled onto the paper, the toner is transfered to the paper The paper is heated to fuse the toner onto the paper.

First write down a word to bridge to Then add #1 to a register then do what you want to be looped then compare the register to the number of times you want it looped + 1 and if they arent equal bridge to the word

The operation e.g. ADD, LDR

THe data being used e.g. a number or an address

A language that is very similar (or based upon) the instruction set of the computer requiring very little translation

High level languages are similar to human language.

A series of instructions to solve a problem that always terminates