1.2:MEMORY AND STORAGE PWH Flashcards
What is a synonym for memory?
Storage
What are the three categories of memory?
Primary
Secondary
Tertiary
What is contained in the primary storage?
Cache
Registers
ROM
RAM
Where is the primary storage located?
Close to the CPU
What are the characteristics of RAM?
Fast access
Volatile
Contains current programs and instructions
Link between the CPU and hard drive
What are some characteristics of ROM?
Non volatile
Contains essential commands
Contains POST and BIOS
What is virtual memory?
The use of secondary storage as memory when the RAM is full
What is a disadvantage of virtual memory?
It is much slower than other types of memory
The capacity is set by the operating system is around 1-2GB
What are the three types of secondary storage?
Magnetic
Solid state
Optical
Which examples of secondary storage can be used in magnetic storage
HDD
Tape
Which examples of secondary storage can be used in solid state storage
SSD
Flash Drive
SD card
USB
Which examples of secondary storage can be used in optical storage
CD
DVD
Blu-ray
What are the 6 dimensions to compare storage?
Cost (£/Gb)
Capacity
Portability
Speed (Gb or Mb/s)
Durability (Read/write)
Resiliency (Sturdy)
What are tracks?
The name of the concentric circles on the HDD
How does magnetic storage read and write data?
Disk heads mounted on mechanical arms
How are the 1s and os stored in magnetic storage?
polarities
What are the pros of magnetic storage?
Cheap
Large storage capacity
Fast access speeds
What are the cons of magnetic storage?
Not robust
Life span of 4-5 years
Slower than others
What are the cons of magnetic storage?
Not robust
Life span of 4-5 years
Slower than others
How is the data stored in optical storage?
In binary in a spiral from the middle out
Grooves (0)
What are the 4 layers of a CD?
Label
Acrylic
Aluminium
Plastic
Which layer does the laser reflect off?
The aluminium layer
Where does the laser hit if it if is a 1
The sensor
What are the pros of optical storage?
Cheap
Portable
Easy to produce
What are the cons of optical storage?
Less storage
Slow write
Easily damaged
Non volatile can also be called?
Persistent
How does solid state storage read and write data?
Trapping electrons
What are the pros of solid state storage?
Fast access
Robust-no moving storage
Portable-physically small
What are the cons of solid state storage?
Expensive
Limited read/write
what is metadata?
data about data
the data stored in a file alongside the actual files data identifies stuff like:
the type of image,
when it was created,
who it was created by,
the image dimensions,
the colour depth
what is lossy compression?
permanently removes some data
used for sound (some sounds can’t be heard
used for images (removes tiny details like colour differences)
what is lossless compression?
eliminates redundant information without losing quality
the algorithm finds groups of repeating data and records the data once along with the number of repetitions
RUNLENGTH ENCODING
what are the benefits of compression?
smaller files = fewer packets = faster transmission time
the stream will decompress when playing
reduces download times-^
makes streaming possible
images in websites appear faster
reduces space on disk/server
What does a binary shift to the right do?
Divide a number by 2
How many bits does ASCII use
7
How many bits does extended ascii use
8
How many bits does unicode use per character?
161
what is bit depth
the number of bits per pixel
how is resolution measured
dots per inch DPI
how is resolution calculated?
the number of pixels in an area (wxh)
what is colour depth
the number of bits available to show the colour of each pixel
how many colours can you fit in 5 bits
32 (2^5)h
how do you calculate the bits used
no. of pixels x colour depth
how do you calculate file size
sample rate x bit depth x duration
