1.2 memory and storage Flashcards
RAM
RAM stands for Random Access Memory. It is also referred to as the computers Main Memory. This is because it is the memory that the CPU has direct access to.
The job role of RAM is to store all the computers open programs and
files. When a program/file is loaded up, it is opened from Secondary Storage and stored in the RAM. This is so the CPU can access the program/file and its data quicker.
The process for loading up a program or file is:
- The user clicks on a program or file to open it up
- The program or file is loaded from the hard drive (Secondary Storage)
- It is stored in the RAM so the CPU can access it quickly
- The user uses the program or file
- Once finished, the user closes down the program or file. It is then removed from the
RAM, and stored back in the hard drive
ROM
Read only memory.It can only be read and is not rewritable(cannot be changed).
stores the program required for botting up the computer system-called BIOS(BASIC INPUT/OUTPUT SYSTEM)
What did BIOS store
all the instructions for the computer system to boot up and work.
Operating system
allows the user to interact and use the device.
Difference between ROM and RAM
RAM is volatile,ROM is not
RAM IS REWRITABLE,ROM IS READ ONLY.
RAM is GB-so the device has a large amount of storage in RAM,therefore more programs can be open at once without RAM being filled up quickly.
ROM IS ONLY MB OR KB AS IT ONLY CONTAINS THE BIOS AND THEREFORE DOES NOT NEED TO BE ANY BIGGER
Virtual memory
Sometimes, when a user has a large number of programs or files open at once, the RAM can
become full. Rather than the computer simply stopping anymore programs or files being
opened, the computer makes use of virtual memory.
Virtual memory is used when the RAM becomes full. When this happens, part of the internal
Hard Drive is partitioned (sectioned off) and acts as additional RAM. This allows further
programs and files to be opened and allows the computer to continue to function.
How does virtual memory affect performance
The CPU does not have direct
access to the virtual memory. Therefore, any programs or files that are stored in the virtual
memory must be swapped into RAM (and something else swapped out of RAM and into the
virtual memory) for them to be actively used. This process slows the performance of the
device down.
How to avoid using virtual memory because it affects peffomance of device
upgrade RAM-it would take longer for the RAM to become full
Secondary storage
A non volatile area where programs and files can be saved and will not be lost once computer is turned off.
Three main types of secondary storage
-opticcal
magnetic
solid state
Optical storage
-where a laser is shone at
the surface of the disc, and then processing the reflection from the disc.
Optical Storages are discs, and examples are CDs, DVDs, and Blu-Rays.
Magnetic storage
Data is stored on Magnetic Storage via magnetised dots. Magnetic
Storage often has moving parts. An example of Magnetic Storage is a
Hard Disc Drive (HDD). Another example is a Floppy Disk; however, these
are no longer used due to their poor durability and
reliability.
Solid state storage
Data is stored on Solid State Storage via electricity. It is becoming
increasingly popular as its capacity increases, and its cost decreases.
Examples of Solid-State Storages are Memory Sticks, SSDs, and SD
Cards.
Capacity speed portablilty and durability of Optical storage
Optical – Advantages: Cheap, portable, average durability and reliability
Disadvantages: Small capacity, slow data transfer speed
Capacity speed portablilty and durability of magnetic
Advantages: Large capacity, fast data transfer speed, relatively cheap per unit
of storage
Disadvantages: Not durable, not portable
Capacity speed portablilty and durability of solid state
Solid State – Advantages: Durable, reliable, easily portable, fast transfer speed
Disadvantages: Price can vary depending on the media you choose
the units
BLUE.NARWHALS.BE.KILLING.MY.GREEN.TOMATOES.PERIOD
bit.nibble.byte.kilobyte.megabyte.gigabyte.terabyte,petabyte
unit laws
There are 4 bits in a nibble, and 8 bits in a byte
* There are 2 nibbles in a byte
* There are 1024 bytes in a kilobyte
* There are 1024 kilobytes in a megabyte
* There are 1024 megabytes in a gigabyte
* There are 1024 gigabytes in a terabyte
* There are 1024 terabytes in a petabyte
Why must data be in binary
Computers do not understand sound, or pixels, or letters.
All these must be converted into binary so that the instructions can be understood and
execute
denary to binary
put it in a table and minus until remainder is 0
denary to hex
-put into binary
-put into 2 nibbles
-convert each to denary
-match with matching letter
hex to denary
Step 1 – Convert any letters back to numbers.
Step 2 – Multiply the first number by 16, and the second number by 1.
Step 3 – Add your two answers together.
binary shift
left=x2
right=/2
Character set
refers to all the characters that are defined and recognised by the computer hardware and software.
what does the size of the character set depend on
the number of bits being used per character.the more bits per character used,the more characters can be represented,therefore a bigger character set
ASCII(american standard code for information interchange)
,a total of 127 characters
were covered. This was because the system used a 7-bit encoding system, meaning the
maximum number of characters represented was 127. In extended ASCII, this rose to 255 as
the system used an 8-bit encoding system, increasing the maximum number of characters.
UNICODE
uses up to 32 bits
per character, meaning there are over 1.1 million characters that are in UNICODEs character
set-meaning more characters can be stored
.
whats the problem with a large character set
storing these characters means more storage space is
taken up on your device.
how to calculate the size of a text file
size=bits per character X number of characters
whats an image made up of
a image is made up of millions of pixels
what is a pixel
An individual ‘square’ on an image that combines with other pixels to produce an image
What is the resolution of an image mean and what is the downside of a high resolute image
Resolution refers
to the number of pixels an image has. The more pixels an image has, the better the quality.
However, this of course means a bigger file size which takes up more storage space when
saved.
colour depth
the number of different colours that can be represented in an image
how is colour depth calculated
bits per pixel. The higher the number of bits per pixel, the more colours that can be
represented in the image. However, once again, the higher the bits per pixel the greater the
file size.
possible colours=
2^number of bits per pixel
What is metadata
e additional data stored with
the image that allows the device to rebuild the image, as well as provides some useful
information to the user
examples of data stored in metadata
the height of the image (in pixels), the length
of the image (in pixels), the bits per pixel, GPS location
image size
colour depth x width x height
how is a sound transmitted through the air
as an analogue wave that mist be converted to a digital waved so it can be stored into the computer as binary.
a process called analogue to digital conversion ADC
What actually happens in ADC
at intervals, takes a measurement of the frequency of the wave. These measurements are
then joined together to create a digital wave
What does more samples mean
The more samples we do a second the better the quality
of the sound, but the more information we are storing per second and therefore the file size
increases.
bit depth
number of bits stored for each sampleThe greater the bit depth, the more accurate the sound will be represented in the
digital wave, and therefore the better the quality of the sound. However, just like the sample
rate, the higher the bit depth the greater the file size.
size of a sound file
sample rate x duration x bit depth
What is compression
reducing the size of a file by changing some of its attributes-like file type or dimensions
Whys is compression used
To allow for additional room on a storage device
Lossy compression
This is when the size of the file is reduced, however the quality
of the file also reduces.The data discarded cannot be regenerated
Lossless compression
This is when the size of the file is reduced, however the
quality of the file remains the same.The information discarded can be regenerated.
