Secondary Storage/Units

Why do you need secondary storage

• A computer needs secondary storage for long term storage of programs and data that are currently not in use 

• Secondary storage is needed as ROM is read only and RAM is volatile

• Secondary storage holds the programs and data whilst the computer is turned off (non-volatile)

• Performance of secondary storage is slower than primary storage but capacity is much higher which makes it perfect for backup & archive of data files

What are the characteristics of secondary storage?

-Capaxity

-speed

-Cost

-portability-How easy is it to move around

-durability-How robust is storage

-Reliability-Probability device will consistently perform function

What are the three types of secondary storage

• Magnetic

• Solid State

• Optical

What is Magnetic storage and properties

• Magnetic storage is a type of non-volatile media that uses magnets (polarity) to store binary 0s and 1s

• Advantages/disadvantages

• Capacity High storage

• Durability Moving parts can get damaged if dropped

• Cost - Low per gigabyte

• Portability Heavy & bulky making them less convenient for transport

• Speed - Moderate read/write access 

• Reliability - Prone to mechanical failure Noise Loud (spinning disks)

What is Solid state storage and properties

• Solid state storage is a type of non-volatile media that uses electronic circuits to store binary 0s and 1s

• AdvantagesDisadvantages

• Capacity -Medium/high storage

• Cost - Very high per gigabyte

• Speed - Very fast read/write access

• Reliability - Limited read/write cycles

• Durability- No moving parts 

• Portability -Small and no moving parts

• Noise -Silent  

What is a optical storage

• Optical storage is a type of non-volatile media that uses lasers to burn the surface of a disk, creating pits and lands suitable for storing binary 0s and 1s

• Advantages/Disadvantages

• Cost - Very low per gigabyte

• Capacity Very low

• Durability No moving parts

• Speed - Very slow read/write access

• Portability Small and no moving parts

• Reliability - Prone to scratches

• Noise-Silent  

Name the units of storage

• Bit-0 or 1

  Nibble-4 bits

  Byte(B)-8 bits-A single character

  kilobyte(KB)-1000 bytes-A small text file

  Megabyte(MB)-1000 Kilobytes-A music file

  Gigabyte(GB)-1000 Megabytes-A high definition movie

  Terabyte(TB)-1000 Gigabytes-A large hard drive

  Petabyte(PB)-1000 Terabytes-A large data centre

What does computer use binary to function

• A computer is built using switches that can either be on or off, this fits the binary number system which only has two digits (1/0), which means off can be represented by a 0 and on can be represented by a 1

• This means all data must be converted to binary before a computer can understand and process it

• Converting data to binary allows computers to process it at an incredible speed, perform complex calculations and store vast amounts of data efficiently

What is data capacity and examples that can be stored

• Data capacity is the maximum amount of information that a storage device can hold

• If you know the capacity of a storage device, you can calculate how much of different data types can be stored

• Examples of data that could be stored include text, images and sound files

How to find text file size

Bits per character) x (Number of characters)

How to find sound file size

Sample rate(Hz) X duration(s) X bit depth

How to find image file size

Colour depth X image height(px) X image width