YEAR 1 CO1 WEEK 8 INPUT, OUTPUT AND STORAGE Flashcards
Describe Solid State Media or Flash Media.
Flashdrives (memory sticks) are examples of a SSD.
They are made up of programmable ROM chips and semi conductors.
Holds data using electronic switches,
if switches are open represents a 1 and if closed represents a 0.
Describe Optical Storage.
Generic name for CDs, DvDs and Blu-Ray.
Optical disk made up of single track that starts in middle and works its way to edge of the disk.
Data is read from or written to using laser.
Describe how laser reads data off a optical disk.
When data is written to read only disk it is encoded as a series of bumps (pits and lands) within the track.
Pits and lands represent the data. Read by a laser which interprets them as different electrical signals.
Describe how a laser writes data onto a optical disk.
Photosensitive dye is used instead of pits and lands.
When writing to disk laser will alter state of dye spot making it opaque.
Dye reflects certain amount of light.
Write Laser alters density of dye and read laser interprets the different densities.
Describe magnetic storage.
Made up of hard metallic material and hermetically sealed.
Made up of number of disks arranged in stack, coated with thin magnetic film material so can change direction of magnetism represented by 1s or 0s.
Describe the structure of magnetic storage.
Surface of each disk organised in concentric tracks and each track split into sectors.
Each sector has the same capacity and a large file will be stored over a number of sectors.
OS groups sectors together into cluster to make storage easier to manage.
State the advantages of Magnetic Storage.
High capacity measured in Tb
Very cheap cost per Gb
Random Access
High Speed Access
State the negatives of Magnetic Storage.
Susceptible to magnetic field interference.
Moving parts.
Not portable.
Read/write speeds slower than flash.
State advantages of Optical Storage.
Cheap if storing less than 10Gb.
Immune to magnetic fields.
Very portable.
State negatives of Optical Storage.
Very expensive to store huge amounts of data.
Can scratch/ be damaged easily.
Read speeds slower than magnetic.
Write speeds are slow.
Not as portable as flash.
State advantages of Solid State Media.
Very portable.
Very durable.
Large capacity.
Silent.
Read/write speeds faster than magnetic.
State negatives of Solid State Media.
More expensive than magnetic.
Limited number of write cycles.
Describe function and properties of RAM.
Used as temporary store for data and instruction which are currently in use.
Is volatile meaning contents of RAM are lost if power supply is interrupted .
Can be accessed non sequentially (random access).
Describe what DRAM is and it’s properties.
Standard RAM module that you are used to seeing, which used for main memory as inexpensive.
Needs a ‘refresh signal’ to keep it’s capacitors charged or will use its contents.
Describe what SRAM is and it’s properties.
Commonly used for the cache as its much faster to access than DRAM.
Although more expensive it doesn’t require ‘refresh signal’.
