7. Storing Data

• The processor fetches data and instructions during the fetch-execute cycle.

  The processor can only process digital data.

  Digital data is made of on/off signals that can be represented using binary numbers
• What is a file?

  A collection of data or instructions
• Data file holds?

  Holds text,image,sound,video

  Read the file , write to the file
• Software file holds?

  Holds instructions

  Run the file - carry out instructions
• Give 5 features of Primary Storage aka Memory?


  -Holds digital data and instructions

  -Uses on/off electrical signals

  -Needs electricity to work

  -If electricity is turned off the contents of memory are lost (volatile)

  -Faster access
• Give four features of secondary storage aka Storage?


  -Holds digital data and instructions

  -Uses a method of storage that does not need electricity

  -Keeps a copy of data and instructions when they are not in use

  -Slower access
• Purpose of memory?

  Processor can fetch digital data quickly from memory
• Purpose of storage?

  Keeps digital data so it is not lost when the computer is turned off
• What is virtual memory?


  When storage is used as memory

  (access to virtual memory is slow , so if a computer uses virtual memory it will go more slowly)
• Explain why virtual memory may be needed?

  If you open too many files the computer can run out of space in RAM. When this happens the computer has to use storage instead of memory.

  The files the computer needs are sent to storage

  Computer must fetch them from storage instead of from RAM
• Three ways to store files without electricity / Storage Devices?

  Optical

  magnetic

  solid state / flash
• Examples of optical,magnetic,solid state?


  optical - e.g CD,DVD,BluRay

  magnetic - e.g hard drive of a computer , magnetic tape

  solid state - e.g USB stick , solid-state drive , SD card
• How does optical storage work?

  -Holds data using pits burned into a plastic surface

  -It is read by a laser beam
• How does Magnetic storage work?

  Holds data using grains of magnetised metal
• How does solid state storage / flash memory work?

  Holds data using electrons trapped in solid matter
• Pros and cons of Optical Storage?

  Pros - Cheap to buy , light to carry and portable

  Cons - Cannot be wiped and reused usually , slow to access data , low capacity compared to other types of storage
• Pros and cons of Magnetic storage?


  Pros - High storage capacity , Quick to acccess data , hard disks perform better if defragmented

  Cons - Has moving parts which eventually fail , Takes up space , can be broken if dropped
• Pros and cons of Flash / Solid state storage?


  Pros - Small and light , No noise , Low power consumption , No need to defragment as there are no moving parts

  Cons - Limited number of read/write cycles , expensive compared to other types of storage , more medium and limited storage capacity
• Uses for optical,magnetic and flash memory?

  Optical - distributing music , games , videos

  Magnetic - hard disk of a desktop computer

  Flash - Personal storage , mobile devices
• What is cloud storage?

  Online storage for files and data.

  held remotely on a large computer owned by a company such as google or microsoft.