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Computer Science Chapter 2 - Coggle Diagram
Computer Science Chapter 2
Primary, Secondary and Tertiary Storage
Secondary Storage
Secondary storage is also needed for things such as:
Storage when the computer is turned off
Backup data files
Archive data files
Semi-permanent storage of data that can be changed
Secondary storage is vital, because primary storage is usually either the ROM (read only) or the RAM (volatile)
Programs not used by the processor are on secondary storage
Examples
Hard disc
Memory stick
Optical: CD / DVD
Tape (v. old)
Tertiary Storage
Where the long-term backup or archive files stored
Tertiary storage is kept incase the main data storage is corrupted or lost
Archives are data that are moved from the main files to free up space, but still has to be kept for long periods of time
Primary Storage
The immediate memory the processor has access to
Examples
ROM
RAM
Cache
Registers
RAM and ROM
RAM
For programs that are being executed by the processor
Holds operating system
Temporary storage of instructions and data
Disc data loaded onto RAM or it would be too slow to execute
Key Differences
ROM is much smaller in comparison to RAM
ROM is read only, but RAM is read and write
ROM is non-volatile and RAM is volatile (loses its stuff when computer is turned off)
ROM
Contains first instructions for the computer when turned on:
To check hardware is installed correctly
Load basic input output system
First instructions are also known as the bootstrap
Software stored on ROM is referred to as firmware
Soldered to the motherboard
In some computers the ROM can be changed in order to change the program being executed, e,g, games cartridge
Small piece of memory
Programs sometimes stored here in embedded systems
Cloud Storage
Disadvantages
You can’t access your files if you don’t have an internet connection (unless you do a local backup)
It can be expensive, with a typical monthly or yearly subscription fee
Advantages
You can access your files from anywhere, assuming you have an internet connection
Automatic backup is possible
Files won’t take up space on your hard drive
You can collaborate on files easily
Basic Info
They can be accessed from all over the internet
They typically use magnetic drives
They are remote servers that store data
Solid state drives are becoming increasingly popular
Advantages and Disadvantages of Secondary Storage
Magnetic
Good for fast access to data
It’s cheap
Good for high storage
Good for cloud server farms
Solid State
Good for rugged, portable devices
Good for small-medium storage
Good for low power, embedded systems
Good for silent operation
Good for fast access to data
Good for small and lightweight devices
Optical
Good for large scale, read-only data distribution e.g. music
Not good for moving / bumps
Good for small storage
Common Types of Secondary Storage
Key Components
Drive: reads and writes to the secondary storage
Media: what the data is actually stored on
Main Types of Secondary Storage
Solid state
Choice of media
Solid state drive
Flash memory
Memory stick
Pros
No noise
No moving parts - reliable
Medium storage capacity
Very quick access to data
Low power
No need to defragment
Solid state drive
Works by a flow of electricity forcing electrons into a floating gate between 2 oxide layers
This causes a change in the charge which can be measures with 1 or 0
Cons
Limited number of read / write cycles
Expensive
Magnetic
Choice of media
Hard disc
Tape
Pros
High storage capacity
Quick access to data
Magnetic drive
Works by having a north and south, this is switchable and readable as 1 or 0
Cons
Has moving parts which will eventually fail
Works better defragmented
Optical
Choice of media
CD-R: compact disc read
CD-WR: compact disc read write
DVD-R: digital versatile disc read
DVD-WR: digital versatile disc read write
Blu-ray: designed to supersede DVD with larger storage
Pros
Lightweight, portable, thin
Optical drive
Works by shining a laser at the media and processing the reflection
There are "pits" and "land" on the media which change the output of the laser
Cons
Slow to access data
Small storage capacity