Chapter 6 - Storage devices
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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