topic 6- memory and data storages Flashcards
MIDI (1)
-Standard adopted by the music industry for controlling devices such as synthesizers and sound cards.
Mp3 (4)
- File compression system for music which does not noticeably affect the quality of the sound
- Removes sound humans can’t hear well
- If two sounds playing at the same time the softer sound is removed
- Uses perceptual music shaping
Differences between MIDI and Mp3 (7)
- MP3 a digital recording of sound
- Mp3 produced by recording software
- Mp3 a compressed file format
- MIDI Instructions of how to make sound
- MIDI Non-audio recording
- MIDI File created using digital musical instruments
- MIDI Produced by synthesizer
Mp4(1)
its a video format lol mr thomas didnt write shit
Jpeg(1)
Picture format
Image capture(6)
- Image converted from analogue to digital (ADC)
- Image turned into pixels
- Each pixel given binary value
- Each pixel given a colour
- Pixels form a grid
- Pixels stored in sequence
Types of file compression (2)
- Lossy
- Lossless
File compression (1)
-Uses a compression algorithm
Advantage of compressing(3)
- Smaller file to transmit
- File transmitted quicker
- Uses less bandwidth
Lossless (6)
E.g. computer program
- Code must be exactly the same as the original
- If not the same as original file will not work
- A (compression) algorithm is used
- No data is removed in the process
- Repeated words (are identified) and are replaced by an index
- The number of times the word appears is stored
Lossy (4)
E.g. Video file (Mpeg)
- Makes the file smaller than lossless
- Quality can be reduced but the file will still run
- Redundant data can be removed
- Used when no requirement for file to be exactly same as original
Compressing text files (4)
- Use lossless
- Repeated words can be indexed
- Repeated words sections e.g. ‘ou’ can be replaced with numerical value
- Can be saved as zip file
Ram types (2)
- DRAM
- SRAM
DRAM(8)
- Constructed of tiny capacitors that leak electricity
- Requires a recharge every few milliseconds to maintain its data
- Inexpensive
- Slower SRAM
- Can store many bits per chip
- Uses less power
- Generates less heat
- Used for main memory
SRAM(8)
- Constructed of circuits
- Hold its contents as long as power is available
- Expensive
- Faster than DRAM
- Can store many pits per chip
- Uses more power
- Generates more heat
- Used for cache
ROM(4)
- Non-volatile memory chip
- Primary memory
- In a microprocessor holds the BIOS
- Can’t be written to
Types of ROM(3)
- PROM (Programmable read-only memory) – It can be programmed by user. Once programmed, the data and instructions in it cannot be changed.
- EPROM (Erasable Programmable read only memory) – It can be reprogrammed. To erase data from it, expose it to ultra violet light. To reprogram it, erase all the previous data.
- EEPROM (Electrically erasable programmable read only memory) – The data can be erased by applying electric field, no need of ultra violet light. We can erase only portions of the chip.
EEPROM(4)
- NAND
- More expensive
- Faster read
- Erase singular byte
SSD (4)
- NOR chips
- Less expensive
- Slower read
- Erase blocks of bytes
Cache (5)
- Cache holds the information from the RAM that is most actively used, and accessed most frequently.
- The computer system will run faster as the slower main memory will need to be accessed less frequently.
- When the processor needs to read from the main memory, it first checks if a copy of the data exists in the cache.
- If the data to be read do not exist in the cache, the data are first copied to the cache and then used.
- When the processor needs to write to the main memory it does so through cache memory.
Remote control car example
-RAM
Contains instructions currently in use
-ROM
Contains the startup/bootstrap program
-SSD
Stores program data to operate the car
Types of secondary storage (2)
- HDD
- SSD
HDD(6)
- Uses platters
- Platters divided into tracks
- Platter is spun
- Read write arm moves over platter
- Magnetic fields control magnetic dots of data
- Magnetic field determine binary value
SSD(2)
- Non-volatile memory
- Uses NAND flash memory
Why SSD>HDD(6)
- No moving parts (more reliable in a portable device)
- Use less power
- Smaller (good for portable devices)
- Faster data access
- Run cooler
- Run quieter
Why HDD>SSD for webservers
- Cheaper for large amounts of data
- Greater longevity for read/write functions
- Don’t need faster speed of SSD
- Expensive to change technology
Optical storage examples(3)
- CD
- DVD
- Blu Ray
DVD(3)
- Uses 1 spiral
- Red laser used to read/write
- Dual layer technology
DVD-RAM(2)
- Uses concentric tracks
- Allows read/write operations at same time
DVD-R Vs DVD-RAM(4)
- DVD-R one spiral track DVD-RAM several concentric tracks
- DVD-RAM can be written to and read at same time;DVD only allows read
- DVD-R only allows read; DVD-RAM allows read and write
- DVD-RAM can have direct access because of concentric tracks
Blu Ray (2)
- Uses blue laser
- Uses single1.1mm polycarbonate disc
Blu Ray vs DVD
- Larger Capacity
- Blue laser rather than red laser
- Single polycarbonate layer not two layers
Tape vs SSD in severs (5)
- Greater longevity – more read and writes
- Speed is sufficient
- Cheaper per unit of data – better value
- No portability requirement
- Trusted technology
two more types of portable storage
portable HD
USB flash drive
