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1.2 comp sci memory+ storage - Coggle Diagram
1.2 comp sci memory+ storage
1.2.1 primary storage
primary storage: main memory acessed directly by cpu and operate very fast so read write very quickly 2 types ram and rom. Expensive little small storage
RANDOM ACESS MEMORY: currently running aplications data currently being used held my ram it is volatile so lose data when turned off can be read and written at any location faster than hardisk more storage compared to rom
Read only Memory: non volatile so saved , small piece of memory in the motherboard contains very first instruction for computer (bootstrap) checks that the hardware is functioning correctly then loads the computer's operating system. Because the BIOS is always needed it is stored in ROM.
hard disk space more cheaper than RAM so more stored
virtual memory needed when not enough phyical RAM so store data. is held on hard disk. when program not being used transferred from ram to virtual memory. transferred back when needed
Flash memory is a type of memory technology that can be used to create primary or secondary storage. It is commonly used to make Read-Only Memory (ROM), and Solid State Drives (SSDs). has no moving parts usally faster. short lifetim can only be rewriten certain number of times
1.2.2
secondary storage
it is non volatile can be used to save and store data that can be acessed repeatedly . not directly embedded into the motherboard and so further away from cpu so slower to acess then primary
needed because rom is read only not enough storage and ram is volatle
capacity:maximum amount of data can be stored. durability: strength of device to last without breaking . portability: easy to carry around. cost:average price . reliability: will work well over time
optical:They can store large quantities of data, so are suitable for multimedia files such as music and films.Many computers have optical drives built in.They are relatively cheap. The discs can easily be transported from one device to another.The discs are quite fragile and can easily be scratched or broken.Access speed is slower than hard drives or solid-state drives.They do not have as large a memory as most hard drives
magnetic: They can store very large quantities of data.
They are faster to access data than optical drives.They have a relatively long lifespan.They rely on many moving parts. Not durable.Head crashes can be disastrous for the huge amount of data saved. They are often noisy in operation also generate hear
solid state:They are very robust as they have no moving parts.They give faster access than hard drives or optical drives.
They are lightweight so suitable for cameras and phones.
.They do not require as much power as hard drives.
.They are an expensive form of storage.They have a limited number of ‘write cycles’, so may not last as long as other storage methods.
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1.2.3 units
computers only understand binary so 0 and 1
binary
8 bits make a byte (B) – the binary number 01100101 has eight bits.
1000 bytes make a kilobyte (KB).
1000 kilobytes make a megabyte (MB).
1000 megabytes make a gigabyte (GB).
1000 gigabytes make a terabyte (TB).
1000 terabytes make a petabyte (PB
4 bits make a nibble
capacity : number of files * single file size
1.2.4 data storage
Denary to binary
binary to denary
binary addition
hexadecimal to biinary
character: everything in character must be in binary character set represent characters in a computer . ASCII USED 7 BITS 128 CHARACTERS featured lower case upper case ! ? but didn't have these feature $ so extended ASCII introduced which was 8 bits. Not everything able to create So UNICODE Introduced access to billions of character take up most storage space 32bits.
image: made up of a thousand pixels. increase resolution higher quality picture. Images stored in 2 different ways bitmap and vectors. Bitmap is image made up of different coloured squares . Each square represents binary value. Vector is a mathematical way of storing images.metadate is ? Information about an image, recorded at the time the image was made. It includes a great deal of data such as camera settings, size and dimensions of the image.size of image file = image height
image width
colour depth. Each square is a pixel. Colour depth/bit depth number of bits used to represent colour in a pixel. more bitdepth larger file size. better resolution higher file size
compression:reduce size of file so it takes up less space
lossy
is where some data is removed or discarded so reducing overall amount of data and size of the file. Image can be compressed by reducing colour depth , so reduce range of colours, similarly audio and video can be compressed in the same way
lossless
some files were do not want to lose data like: text files, spreadsheets financial records and emails. so file size reduced without removing data but not same file size reduction and lossy. can rearrange the code to put all repeating units together.
sound:
sound us recorded by a computer its amplitude is recorded at regular intervals. analogous signals represented as waves. the number of bits used to store sample is known as sample size. the number of sample taken per second know as sampling rate. Quality of the audio : increasing sampling rate with increase quality and the file size also increase sample size with increase file size. Bit rate is amount of data stored per second of audio also calculated by sample size * sample rate