Chapter 6 - Storage devices Flashcards
What are the 2 types of primary storage?
» RAM and ROM
What is primary memory?
» The component of the computer that holds data,programs, and instructions that are currently in use
What is RAM?
» Volatile peice of memory that holds programs and instructions that are currently in use
What is ROM?
» A non-volatile piece of memory that holds the bootloader - such as the BIOS
What are the 4 features of RAM?
» It is Volatile
» Can be read from or written to
» Stores the parts of the operating system, programs and data that are currently in use by the computer
» Larger capacity then ROM
What are the 3 features of ROM?
» It is non-volatile
» It is read-only
» Often used to store the computer’s boot prgoram
What does RAM stand for?
» Random access memory
What does ROM stand for?
» Read-only memory
What is the definition of volatile?
» It means that it loses its contents when electrical power is lost
What is virtual memory
?
» When the computer’s RAM may not be not large enough to store all these programs
» Hard disk is used as an extension of memory
Where is virtual memory held?
» On the hard disk
What are the benefits of virtual memory?
» Reduces the need of phyisical hardware increasing memory
» Storage can be backed up - people around the world can access data
» Allows more programs to be run
When is virtual memory used?
» When there is an insufficient amount of RAM
» Data is moved to RAM which is currently not in use, moved back to RAM when needed by the computer
What are the disadvantages of virtual memory?
» Very slow
» Can cause disk thrashing
Which is faster secondary storage or primary memory?
» Primary memory
Why is secondary storage needed?
» To keep programs and data indefinitely
What are the 3 types of storage devices?
» Magnetic
» Optical
» Flash
What is the purpose of toggling a state without power?
» To represent either 1(which is on)
» To represent either 0(which is off)
What are 2 examples of magnetic storage?
» Hard disk drive
» Magnetic tape
How does a hard disk work?
» Rotating platters coated with magnetic material
» Ferrious iron particles on the disc are polarise to become either a north or south state - represents 0 or 1
» Disk divided into cocentric circles - divided into sectors
» Like an old record player - moves around at 10000RPM to access diferent sectors
How is data read from or written to in a hard disk?
» As it passses under the drive head
How do magnetic storages mainly work?
» Uses a magnetisable material. Patterns of magnetisation are then used to repreent binary sequences
What are the advantages of Magnetic storage?
» Fairly cheap
» High in capacity
What are the disadvantages of megnetic storage?
» Susceptible to damage if dropped
» Vunerable to magnetic fields - strong magnetic filed may erase the data
» Very slow compared to SSD
» Not portable - movements can cause them to malfunction
» Consume more power then flash media
What are the 3 different formats that Optical disc come in?
» CD - ROM - read only
» CD -R - recordable
» CD-RW - rewritable
What does CD-R mean?
» Can be written to once
What does CD-RW mean?
» Can be read to and written to many times
How does an optical disk work?
» Using a high powered laser to burn sections of the surface, which represents 1s and 0s
What are 3 examples of Optical storage?
» Compact disc (CD)
» Digital versatile disc (DV)
» Blu-ray disc
How much data does a CD-ROM usually hold?
» 700MB of data
How much data can a Blu-ray disc hold?
» 50GB
How come Blu-ray disk hold much greater storage then CD-ROM despite being the same CD size?
» The shorter the wavelength of the laser - creates much smaller pits
» Enabling a much greater number to fit in the same space
What is CD-ROM?
» Data cannot be overwritten
What are the advantages of Optical storage?
» Cheap
» Portable
What are the disadvantages of Optical storage?
» Easily damaged due to scratching
» Has a much lower capacity compared with other storage devices
How does flash memory work?
» Specital type of read only memory that uses electronic circuits to represent data
What are the advantages of flash devices?
» Very fast
» Robust
» Durable
» Low power consumption
What are the disadvantages of flash memory?
» Expensive
» Sometimes have a certain numer of read/write times
What are 3 examples of flash memory?
» USB memory stick
» Camera memory card - Micro SD card
» Solid state drive
What comparison factors do storaged devices compare on?
» Speed
» Durability
» Cost
» Capacity
» Portability
» Robustness
How many bits are in 1 nibble?
4 bits
How many bits are there in 1 byte?
» 8 bits
How many bytes are there in 1KB?
» 1000
How many kilobytes are there in a Megabyte?
» 1000
Why are Solid state drives replaceing Hard disk drives?
» SSDs are ligher - so much more suitable for portability
» Data access is faster
» Less power consumption - more energy efficient
What is the typical size for a CD?
» 650MB
What is the typical size for a DVD?
» 4.7GB
What is the typical size for a Bluray?
» 25 - 100GB
What is the typical size for a HDD?
» 1-20TB
What is the typical size for a SSD?
» 500GB-5TB
What is the typical storage for a magnetic tape?
» 10-30GB
What is the typical size for a USB flash drive?
» 16GB- 1TB
What is firmware?
» The phyiscal hardware inside the computer
