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MEMORY, STORAGE DEVICES AND MEDIA (RAM It is the primary storage that…

- - - - THREE TYPES OF STORAGE
        
        OFF-LINE STORAGE
        
        PRIMARY STORAGE
        
        known as memory, it is the kept where data is ready for processing, the capacity is quite small
        
        two parts of primary storage : RAM(random access memory) and ROM(read only memory)
        both types are memory chips
- - - - EMBEDDED COMPUTERS
        
        They have a few kilobytes of RAM like pocket calculators. They only need small amounts of data to process.
      - GENERAL PURPOSE COMPUTERS
        
        They have a few gigabytes of RAM like desktop PC'S. this is because it will hold the operating system and data that is being processed
- - - - General purpose devices use ROM to hold software known as bootstrap. The bootstrap contains instructions that determine the basic hardware structure of the computer
        
        Certain types of ROM can be erased and re-written to. This type of ROM is known as
        (EPROM) erasable programmable read only memory
        
        this is found in situations where a device's firmware may need to be upgraded at some point in the future. Fr example smartphones all have firmware that can be updated by the user.
        
        Upgrading firmware is known as flashing
- - - - Magnetic storage devices are read, write and erase data by using electromagnets and magnetic fields to control tiny magnetic dots of data, the dots represent binary
        
        TAPE BASED
        
        They use a cartridge of looped magnetic tape. The magnetised data dots are stored in series along the length of the tape.The tape passes over a electomagnetic read/write head that writes, reads or erases the magnetic dots
        
        the rate at which data is moved from a storage device is called data transfer rate.
        
        DISK BASED
        
        Disk based devices such as hard disk drives consists of several disks known as platters.
        platters can be metal or glass. They have a magnetised coating on which data dots are stored. they lie in tracks, they are attached to a rotating spindle, it spins at high speed, data is processed as they pass the moving arm, it moves in different tracks.
        
        hard disk drives are the most common form of secondary storage device.
      - magnetic storage
        
        optical storage
- - - - the process of recording data onto an optical disk is known as burning. This is because the laser burns the pits into the disk surface. they have good data transfer rate with speeds ranging between 10 ad 7 megabytes per second.
        
        Newer formats, such as BLU-RAY, are far quicker than older formats such as compact disk
        
        There are different types of optical disk including compact disks, DVD'S and BLU-RAY DISKS.
        
        DVD devices use a high frequency laser than CD devices. The higher frequency allows the pits and land to be packed tighter onto the tracks. This allows more data to be stored.
        
        BLU-RAY devices use a blue violet laser that operates at a shorter wavelength than the red lasers used in CD and DVD devices. This gives more precision when writing to and reading from a disk.
        
        CD-700 MB
        DVD single layer -4.7 GB
        DVD DUAL LAYER -9.4 GB
        BLU-RAY SINGLE LAYER -25 GB
        BLU-RAY DUAL LAYER -50 GB
        BLU-RAY TRIPLE LAYER -100 GB
        BLU-RAY QUADRUPLE -128 GB
        
        OPTICAL MEDIA TYPES
        ROM-read only
        R-disk is initially
        empty of data
        RW-DISK IS INITIALLY EMPTY OF DATA
        
        Data is stored on an optical medium is more portable than that on a hard disk drive
        
        1 more item...
- - - - 8 BITS= 1 BYTE
        1024 BYTES=1
        KILOBYTE
        1024 KB = 1 MEGABYTE
        1024 MB = 1 GIGABYTE
        1024 GIGABYTE = 1 TERABYTE
        
        THE NUMBER OF BITS REQUIRED FOR DATA STORAGE DEPENDS ON THE AMOUNT OF DATA AND THE TYPE OF DATA TO BE STORED