Unit 1.2 Flashcards
1
Q
Primary storage
A
- known as ‘main memory’ when talking about RAM
- located on the motherboard so that it can be quickly read from and written to
- stores programs and data currently in use
- volatile
2
Q
What does volatile mean?
A
Contents are lost when the power is switched off
3
Q
4 types of primary storage
A
- ROM
- RAM
- flash
- cache
4
Q
RAM
A
- volatile
- read and write
- data and instructions can be stored and accessed from any location in memory
- holds data/instructions currently in use
5
Q
ROM
A
- non-volatile
- read only
- stores instructions/data needed for the computer to run
- usually programmed by the computer manufacturer so can’t be overwritten
6
Q
Flash memory
A
- can be written to and overwritten like RAM
- fast but not as fast as RAM
- needs little power as no moving parts
- idea for droppables
- also used as a external secondary storage
- SSDs and USB memory sticks have flash memory
7
Q
GPU
A
- microprocessor that produces high-quality graphic images on screen
- originally performed by CPU, but introduces as more complex graphics were developed
- built in motherboard
- has its own video memory and card
8
Q
Virtual memory
A
- computer can temporarily use secondary storage as additional primary memory when RAM is full
- when data is needed again, it can be swapped with any un-used data and transferred back to RAM
- makes computer run slower
- more RAM reduces the need for virtual memory
9
Q
3 types of secondary storage
A
- magnetic e.g. hard disk drives
- optical e.g. CD, DVD
- solid state e.g. SSDs and USB memory sticks
10
Q
Magnetic
A
- use magnetic fields to magnetise tiny individual sections of a metal spinning disk
- each section represents a bit, magnetised = 1 and de-magnetised = 0
- can contain many terabytes of data
- fairly cheap
- high in capacity
- dropping can cause a lot of damage
- vulnerable to magnetic fields
11
Q
Optical
A
- uses a laser to dance the surface of a spinning disk
- the disk is divided into tracks with flat areas and hollows (lands and pits)
- when the laser shines on the surface, lands reflect the light and pits scatter the beam
- a sensor looks for the reflected light, lands = 1 and pits = 0
12
Q
Benefits of solid state
A
- fastest read/write speeds
- good capacity
- good reliability but eventually runs out
13
Q
Benefits of magnetic
A
- highest capacity
- highest reliability
14
Q
Benefits of optical
A
- good portability
- good durability
- lowest cost
15
Q
Disadvantages of solid state
A
- highest cost
16
Q
Disadvantages of magnetic
A
- low portability
- low durability
17
Q
Disadvantages of optical
A
- lowest capacity
- lowest speed
- lowest reliability
18
Q
Solid State
A
- uses non-volatile RAM to store data indefinitely
- fast access times
- more durable than devices with moving parts
- can only read/write to it a certain amount of times
19
Q
What are the units of data storage?
A
- bit
- a nibble (4 bits)
- a byte (8 bits)
- 1 KB (1000 bytes)
- MB (1000 KB)
- GB (1000 MB)
- TB (1000 MB)
20
Q
ASCII
A
- developed to encode characters for electronic communication
- only uses 7 bits so could only represent 128 characters
- severely limited
21
Q
Unicode
A
- developed because ASCII was severely limited
- can represent over 1 million characters
22
Q
What is metadata?
A
- information about a file attached to a file
- e.g. author, time created, date, file size, image height, image width
23
Q
How do you calculate image file size?
A
image height * image width * colour depth
24
Q
What is an overflow error?
A
- when you end up with an extra digit after adding binary
- it could cause program to crash OR it might just ignore the extra digit and produce an unexpected result
25
What is the MSB?
- most significant figure
- bit furthest to the left
26
What is the LSB?
- least significant figure
- bit furthest to the right
27
What is a sample?
A sample is a sound wave captured at regular intervals.
28
Hexadecimal
- uses digits 0-9, then A-F
- reduces processing time with hexadecimal rather than binary
- easier and faster to write
29
Binary Shifts
- a left binary shift multiplies the number by two
- a right binary shift divides the number by two
30
What is sound captured at each point converted into?
the nearest numeric equivalent (not a decimal), and then into binary
31
What is sample rate?
- the number of samples recorded in any given period of time
- higher the sample rate, higher the quality of sound
- higher the sample rate, larger the file
- measured in Hz
32
What is bit depth?
- number of bits used to record each sample
- higher the bit depth, better the quality
- higher the bit depth, larger the file
33
What is bit rate?
- a measure of how much data is processed for each second of sound
- higher the bit rate, better the quality
34
How do you calculate bit rate?
bit depth * sample rate
35
How do you calculate sound file size?
sample rate * duration * bit depth
36
Colour Depth
- colour depth of two means four possible colours
- each extra bit per pixel doubles the range of colours available
- the more colours, the more bits per pixel, the more colour depth, the larger the file
37
Resolution
- how tightly packed the pixels are
- low resolution have less pixels, but high resolution images have more
- higher resolution, higher quality
- higher resolution, higher file size
38
Compression
- large files require lots of storage space and can be difficult to transmit, so compression is used
- lossy and lossless
- compression is the process of encoding data so that it needs fewer bytes/bits to represent it
- compressed data must be decompressed to be used, which can be detrimental to some applications
39
Lossy
- some data removed or discarded
- reduces overall amount of data / file size
- e.g. an image can be compressed by reducing colour depth
- decompressed file not identical to the original but unlikely to be noticed by humans
40
Lossless
- some files don't want data to be lost e.g. text files, financial records, emails
- files can be reduced in size without data loss
- doesn't reduce the same file size as lossy
- GIFs and PDFs
41
RLE
- run length encoding
- a method of lossless consumption
- stores consecutive runs of the same data as one item instead of many
- e.g. 00000011111111000000, would be 608160
