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Data Storage | O Level Computer Science 2210 & IGCSE Computer Science 0478 | Detailed Free Notes To Score An A Star (A*)

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  • Data Storage
    • Can be temporary or permanent
    • Primary Storage
      • This is the storage that the CPU can access directly
      • 2 main types of primary storages: RAM and ROM
      • RAM means random access memory
      • ROM means read only memory
    • Characteristics of RAM
      • Volatile memory
      • When power turned off, data in RAM is lost
      • Stores data and programs that are currently in use
      • Contents are constantly being changed
      • RAM amount can be increased by adding further RAM components
    • ROM Characteristics
      • Non-volatile memory
      • Power removed even still contents are safe
      • Stores programs that initially bootup the computer such as bootstrap and BIOS
      • Contents of ROM are fixed and not normally change
      • Difficult to reprogram
      • Not easy to alter ROM
  • Secondary Storage
    • Not directly accessed by CPU
    • Data has first to be loaded into the primary memory, and then CPU can access it.
    • 3 main types of secondary storages
      • Magnetic
        • Uses magnetism to store data
        • Circular plates called platters that spin and allow data to be read and written
        • Platters are separated into tracks and sectors
        • Read/ write head that moves across the platters to read or write the data
        • Electromagnet to magnetize dots on each platter
        • If the dot is magnetized, it has a value of 1 otherwise, it has a value of 0
        • Hard Disk Drive
      • Optical Storage
        • Uses lasers to read and write data
        • From a circular disk
        • Laser burns puts into the surface of teh disk
        • Spiral tracks organized
        • Land is the surface of the disk between each put
        • Pits are also read through the laser and data is obtained
        • CD, DVD and Blu Ray use this system
      • Solid State Storage does not have moving parts
      • Semiconductor chips are used instead
      • It is also called flash memory
      • Data is read and written is flhased onto them
      • Cells and transistors are laid out in a grid
      • Wiring can be done in two different ways
        • NOR flash structure uses a parallel structure
        • NAND flash structure uses a series structure
      • Cells are the intersection of the rows and columns
      • One transistor is called the control gate and the other is called the floating gate
        • The control gate is on the top of the floating gate
      • Initially, all transistors have value of 1.
      • Once electric current reaches each control gate, it then flows through the floating gate to be stored.
      • When data is stored in a transistor, it is converted to the value of 0
      • USB also uses solid state these days.
  • Virtual Memory
    • Virtual memory does not have a physical component
    • Memory is the term used for short term temporary storage of data
    • Storage is for permanent store of data
    • Virtual memory is for temporary use
    • Extension to the RAM
    • When a computer is given a large task to do, t will require a lot of data,
    • But if the RAM is restricted, we use a virtual memory.
    • Here, a hard drive component becomes partitioned into a section that is used as a RAM instead
    • Some of the data from the RAM is transferred to this virtual memory until it is needed again.
    • The data that is transferred is then collected in a structure called page
    • Pages of data are transferred to the virtual memory to make sure there is enough room in the RAM for the immediate data that is being processed
    • If the pages are required again, they are sent back to the RAM to be processed
    • If the RAM becomes full and there is no ability to transfer pages, it will crash.
  • Cloud Storage
    • Servers are computers that store up the data a company requires
    • Staff is required for maintenance of such data
    • Instead, cloud storage can be used.
    • Such companies have thousands of servers that are maintained and secured
    • Here, you pay a fee to the company for their service and store data on their server
    • Once the data is required, it is accessed through the internet
    • It uses third party hardware such as computer servers and the data is stored remotely
    • It has become a very easy way for business costs to be reduced
    • It can big risk as well
    • Benefits
      • No payment of hardware
      • Responsibility of the cloud storage company to protect the data
      • Access through internet
      • Can scale the storage per requirement
    • Drawbacks
      • They can lack in security, damaging your data
      • Internet connection not available, then data can not be accessed
      • Scalability can be costly
Hunain Zia

Hunain Zia has previously achieved considerable success in the high-school educational stream, gaining a massive 154 Total A Grades and 7 Major Distinctions, a process in which he broke/ set 11 different world records, including the most A grades ever achieved, most subjects ever appeared in, most distinctions, gaining distinctions across two separate boards (Pearson Edexcel and CAIE) within the same year/ ever, and even 19 hours of constant examination. All records stand intact today. Hunain pursued his Honors Accounting Degree from the prestigious Bentley University, and then completed an LLB (in Honors) from University of London. Currently, he manages multiple social and commercial projects, has founded digital streams and works tirelessly in the education sector.

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