2.3.2 Architecture 2 Flashcards
Primary storage
Memory
Secondary storage
Name given to any device used to hold permanent copy of - save work
- operating system
- programmes
- data
The need for secondary storage
Memory volatile
Then results of processing not stored there
Types of secondary storage
Magnetic
Optical
Flash
ROM
Used to permanently store basic I/o system
- instructions used to power up device and load operating system
RAM
Main memory
- temporarily store operating system, programmes and data being used
CACHE
Form of memory that can be r/w to
High speed volatile memory
Located in CPU
store copies of contents- most frequently used memory locations.
Searched by CPU before main memory.
Enables CPU to process instructions faster.
Magnetic storage media
Data stores as magnetically aligned particles on…
- a read/ write head- platters
How Can magnetic storage media read or write particles by
- moving to the correct sector of the platters which are constantly moving.
- and applying a magnetic force to the particles
- when a programme is loaded or a file opened the 1s and 0s are read and copied into the memory
- the permanent copy remains on the hard disk
- when a file is saved the results of processing are copied from memory and written in a pattern of particles on the sectors and tracks of a hard drive platter.
FLASH
- data is stored electronically on silicon based microchips.
- look very different to RAM memory chips
- transistors contain an extra part that allows for the input/ output kept in transistor to be stored when no power.
- each FLASH device wiped at higher voltage required
- cannot r/w to I definitely.
Typical optical storage media
CD-ROM CDR CDRW DVD BLU RAY
CD-ROM
700mb
CDR AND CDRW
700mb
DVD
4.7gb
Smaller light wavelength used= more circles can fit in
Dual layer DVDs used 2 layers on top of each other.
BLU RAY
25gb
Blue light shorter wavelength than red
Used for HD storage media storage.
Optical storage media
- laser beams are reflected back from the surface of the disk which
- contain pits 0 and lands 1
- the disk spins and data is read by the fixed laser reflector.
- surface of disk is a spiral pattern from the centre of the disk outwards.
- more concentric circles in higher capacity optical media.
- determined by wavelength of light used
- CD DVD BLU RAY used lower and less light wavelengths.
Main memory
Part of internal memory
Immediate access memory
Made up of RAM
C+ C main memory and cache
Both volatile
Cache is a form of RAM- main memory.
Contrast
Main memory- stores a portion of operating system, application software running and other data items needed when carrying out operations.
Cache memory- stores copies of contents most frequently used my memory locations.
Faster than main memory
More expensive
Evaluate primary storage
Called memory
ROM- permanently store basic input output system
RAM aka main memory
Used to temporarily store OS, programmes and data being used and cache- very high speed memory used to store instructions that CPU most frequently needs.
Evaluate secondary storage
Hold long term copies of programs and data we are using so they can be reloaded for use without need for reprogramming- also reload results of previous processing.
Magnetic
Optical
Flash
Some can be moved from computer to computer.