topic 6- memory and data storages

-Standard adopted by the music industry for controlling devices such as synthesizers and sound cards.

• 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

• 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

its a video format lol mr thomas didnt write shit

Picture format

• 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

• Lossy - Lossless

-Uses a compression algorithm

• Smaller file to transmit • File transmitted quicker • Uses less bandwidth

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

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

• 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

• DRAM - SRAM

• 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

• 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

• Non-volatile memory chip • Primary memory • In a microprocessor holds the BIOS • Can’t be written to

• 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.

• NAND • More expensive • Faster read • Erase singular byte

• NOR chips • Less expensive • Slower read • Erase blocks of bytes

• 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.

-RAM Contains instructions currently in use -ROM Contains the startup/bootstrap program -SSD Stores program data to operate the car

• HDD - SSD

• 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

• Non-volatile memory - Uses NAND flash memory