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level: Memory and Data storage

Questions and Answers List

level questions: Memory and Data storage

QuestionAnswer
How is sound stored ?Samples are taken from the analog sound signal. By the ADC, each sample is converted to binary form and stored
What is file format and what does it represent?Three or four letter added to the end of every file that represents 1) What type of data the file contains 2) How the data is stored
What are the factors that affect quality of the sounds stored?Sample rate Sample size
How is sound stored through lossy compression?The sounds which are inaudible to human ear is removed
What is a bitmap?When images are stored, it is divided into pixels, a pixel is the smallest area of the screen that can be changed A file that contains the color of each pixel stored as a binary number Number bits needed to store the color of each pixel depends on the number of colors 2 to the power number of pixels = Number of colors
What affects the file size of images?1) Number of pixels in the image(resolution)- Higher the resolution, better the picture, bigger the file size 2)Number of colors- More the colors bigger the file size
How are images stored through lossy compression?Color variations that the human eye cannot see are removed, reducing the number of colors therefore reducing the number of bits per pixel hence reducing the file size.
How are videos stored?Each minute of video consists of several frames, each frame is stored as a separate bitmap
How does lossless compression work?Repeating characters are identified The replaced with a smaller code A key is added at the end of the file
Give two differences between lossy compression and lossless compressionLoss has a greater compression rate( up to 90%) Unlike lossy no data is lost during compression
What are the three type of storage devices?Primary storage Secondary storage Offline storage
What are the two primary storage devices of a computer?RAM( Random Access Memory) ROM ( Read Only Memory)
What are the features of RAM?RAM is volatile (requires power to maintain stored info) Data s lost when switched off
What are the features of ROM?It is non-volatile User cannot modify, delete; READ only
What is stored into RAM?Running programs Data waiting to be processed Data waiting to be output
What is stored into ROM?Bootstrap loader: Loads operating system BIOS (Basic Input Output System)- data needed by the processor to communicate with I/O devices
What are the advantages of primary store?Faster to access
What are the advantages of secondary store?Permanent Larger capacity
What are the advantages of offline store?Permanent Larger capacity Portable
What are the two types of RAM?Dynamic RAM (DRAM) Static RAM(SRAM)
How does a SRAM work?Data input remains until the user changes or switches off Each bit is stored using a logic gate called a flip flop which is created using two NAND gates or two NOR gates
How does a DRAM work?Data entered degrades ( is lost ) after a short interval and must be entered( approximately 15 microseconds ) Each bit is stored using a transmitter and capacitor Capacitor holds the data Transistor is used to switch between 1 and 0
What are the advantages of SRAM and where is it used?Faster Memory cache : Some memory closer to the processor used to improve performance Registers
What are the advantages of DRAM and where is it used?Cheaper Uses less power Larger capacity RAM in PC
What are the two types of secondary storage?Solid State Drive Hard Disk Drive
What are the three magnetic storage deices ?Hard disk Magnetic tape Floppy disk
What is latency ?Time taken for specific data track to rotate around to the READ-WRITE head
What are the two types of SSD?Flash memory EEPROM ( Electrically Erasable Programmable ROM)
What are the features of Flash memory?Uses NAND gates Cheaper Only one block of data is read or written at a time Majority use this Non-Volatile Rewritable Memory
What are the features of EEPROM?NOR gates Faster Expensive Single Byte of data can be read/written at a time
What are he advantages of SSD over HDD?More reliable No latency therefore faster Lighter and thinner Produces less heat and less power
What is an offline storage?Non- volatile storage devices that can be easily disconnected from computer and stored in a different location
Give four examples of offline storagesCD/DVD/Blu ray ( Optical Drives) Pen drive ( solid state) Portable SSD ( solid state) DVD - RAM
How is data written into an optical device?1)A laser is shone onto the surface of the disk, the surface is normally covered with a thin aluminium layer. 2) The laser burns pits into the Aluminium, the surface is then covered with pits and lands representing 1s and 0s ( data is written to a single spiral track)
How is data read from an optical device?The laser is shone onto the surface The reflected light is captured by a light sensor The amount of light captured for pits and lands are different This is used to recognize between 1s and 0s
What are dual layer DVDs?A DVD which has two layers to which data can be written
What is birefringence?A problem caused in dual layer DVDSs due to the reflected light from the second layer
Why can READ or WRITE be done one at a time with DVDsSince it has only one track
What are the features of a DVD-RAM?Concentric tracks therefore possible to READ and WRITE at the same time Lasts longer than a DVD or a CD Has two layers of polycarbonate
What are the feature of a blue ray ?Uses blue laser which has a shorter wavelength Therefore: Smaller pits; Higher pit density; Increases capacity Has a method of encryption which prevents piracy Higher transfer rate
What are the storage sizes of CD, DVD, Blue RayCD- 650MB DVD- 4.5GB -9GB Blu Ray- >50GB
What are the features of memory sticks( Pen drives)?Portable Used for temporary backups to move data from one device to another Used as security dongle
What are SD( Secure Digital) / XD( Extreme digital)?Used to store data in mobile phones, digital cameras and MP3 players
How is data transferred from SD cards to the computer?1)Connect the device with the card to the computer using a USB cable 2) Transfer the data using a bluetooth connection between the device and the computer 3) Use a SD card reader
Explain why should a SD card be properly disconnected before removal?NAND gate memories write one block at a time, disconnection ensures that last block of data is safe, if it is not disconnected before removal the file maybe corrupted