computer science 1.2 !

what does RAM do??

stores part of the OS and programs/data currently in use

what is RAM?

volatile

what does ROM do?

stores bootstrap (PC setup instructions) and loads the OS into RAM

what is ROM?

read only and non-volatile

what happens when RAM is full? “

part of the HDD is used as if it were RAM

what is the name for using the HDD as if it were RAM?

virtual memory

downsides of virtual memory?

slows down the computer

how can we speed up our computer?

upgrade RAM size, upgrade cache size, terminate programs

what does a left binary shift do?

multiples by 2

what does a right binary shift do?

divide by 2

what is colour depth?

the number of bits available to represent a pixel’s colour

what happens if colour depth is higher?

more bits per pixel and more colours represented (image resolution increases)

how do u calculate colour depth?

2^x (x = number of bits)

how to calculate the size of an image file?

colour depth x resolution

how is sound stored?

the amplitude of an analogue wave is recorded at regular intervals and stored as a binary value

what are the benefits of compression?

file sizes are reduced and more can be stored, file transmission time is shorter

how does compression benefit a website?

compressed files on a web page reduce load times and put less stain on servers (aiding mobile phones and slow connections)

how does lossy compression work?

irrelevant/repeated parts of data are permanently removed from file

how does lossy compression work in sound files?

small / low frequencies that may not be heard by humans are deleted

advantages of lossy?

smaller files than lossless and works well for media files

disadvantages of lossy?

data cant be restored, cant be used with text as it is unrecognisable, clear loss in quality may be visible

how does lossless work?

reduces file size with out removing data. when it is decompressed, it returns to its original quality

advantages of lossless?

can be compressed/decompressed with out a loss in quality, works in all file types

disadvantages of lossless?

files are larger than when done with lossy, takes a long time (uses complex algorithms)

advantages of magnetic secondary storage?

reliable and has a high capacity

disadvantages of magnetic secondary storage?

not durable and very noisy

advantages of solid state secondary storage?

no moving parts so faster access/write speeds, portable, durable

disadvantages of solid state secondary storage?

expensive

advantages of optical secondary storage?

durable and portable

disadvantages of optical secondary storage ?

not durable, low capacity per disk