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1
Q

Define memory dump

A

when memory contents are output to printer/monitor

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2
Q

Uses of binary (3)

A

ASCII value

unicode value

machine code

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3
Q

Advantages of hexadecimal (5)

A

easier to understand

easier to debug

shorter = takes up less space

faster to enter than binary

easier to convert from binary than denary

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4
Q

Define simplex data transmission (2)

A

data transmitted one way only

e.g computer to printer

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5
Q

Define duplex data transmission (2)

A

data transmitted both ways simultaneously

e.g broadband internet

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6
Q

Define half-duplex data transmission (2)

A

data transmitted both ways not at same time

e.g walkie talkie

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7
Q

Define serial data transmission (2)

A

one bit sent at a time over one wire

e.g computer to printer/USB

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8
Q

Define parallel data transmission (2)

A

multiple bits sent at same time using multiple wires

e.g computer to modem/internal computer components

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9
Q

Advantages of serial (4)

A

reliable over longer distances

cheaper

data not out of synchronization

less risk of electrical interference between wires

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10
Q

Advantages of parallel (2)

A

faster transmission

easier to program input/output operations

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11
Q

Features of asynchronous data transmission (3)

A

data transmitted in agreed bit pattern

data bits grouped together and sent with control bits

receiver of data knows when data starts/ends

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12
Q

Features of synchronous data transmission (5)

A

continuous stream of data

data accompanied by timing signal

synchronizes sender and receiver

receiver counts number of bits sent

reassembles into bytes

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13
Q

Advantages of synchronous data transmission

A

faster

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14
Q

Define USB

A

data transmission method

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15
Q

What ASCII stands for

A

American Standard Code for Information Interchange

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16
Q

Number of bits in standard ASCII

A

7 bit codes

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17
Q

Function of ASCII

A

represent letter/number/characters on keyboard

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18
Q

Denary value for a on ASCII

A

97

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19
Q

Denary value for A on ASCII

A

65

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20
Q

Denary value for 0 on ASCII

A

48

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21
Q

ASCII disadvantages

A

does not represent non-western characters

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22
Q

Define unicode (2)

A

coding system

represents characters of all languages

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23
Q

How is sound represented digitally (4)

A

computer samples sound using ADC

amplitude determined at set time intervals

gives approximate sound representation

sound wave sample encoded as binary

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24
Q

Define sampling

A

measuring amplitude of sound wave

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25
Define sampling resolution/bit depth
number of bits per sample
26
Define sampling rate (2)
number of sound samples taken per second measured in hertz
27
Benefits of having larger sampling rate/resolution (3)
better sound quality larger dynamic range less sound distortion
28
Disadvantages of larger sampling rate/resolution (3)
larger file size requires greater processing power longer to download music files
29
How do bitmap images work (3)
made of pixels each pixel represent binary number binary numbers represent colour
30
Define colour depth
number of bits to represent each colour
31
Define image resolution
pixel number in an image
32
Photos with lower resolution will have higher detail than photos with higher resolution True or False?
false
33
Disadvantage of using high resolution images (2)
file size increase increase in download speed
34
Define a bit (2)
basic unit of computing memory storage either 1 or 0
35
Number of bytes in kibibyte
2^10
36
Number of bytes in kilobyte
1000
37
Equation for file size of image
image resolution (pixels) x colour depth (bits)
38
Equation for size of mono sound file
sample rate (Hz) x sample resolution (bits) x sample length (seconds)
39
Uses of hexadecimal (4)
error codes MAC address IPv6 address HTML colour codes
40
Hexadecimal use in error code
values refer to location of error
41
Define a MAC address (3)
number that uniquely identifies device on network first half is manufacturer of device second half is unique serial of device
42
Define IP address
identifies global address on internet
43
Number of bits in IPv4
32 bits
44
Number of bits in IPv6
128 bits
45
Number of bits in MAC address
48/64
46
What does MAC address stand for
media access control
47
Use of HTML in hexadecimal (2)
represent text colors on screen different intensity of primary colors determined by hex value
48
Hexadecimal red
FF 00 00
49
Hexadecimal green
00 FF 00
50
Hexadecimal Blue
00 00 FF
51
Why might one compress data (3)
reduce cost that come with larger file size save storage space reduce download time
52
2 types of file compression
Lossy Lossless
53
Features of lossy file compression
eliminates unnecessary data
54
Lossy file compression examples (3)
Mp3 MP4 JPEG
55
Define mp3
lossy for audio files
56
Define mp4
lossy for multimedia files
57
Define lossless file compression
data from original file reconstructed
58
What does RLE stand for
run-length encoding
59
Structure of packet (3)
header payload trailer
60
Data in packet header (4)
IP address of sender IP address of receiver Sequence number of packet (to reaarange in order) Size of packet in bytes
61
Data in payload (2)
actual data 64 KiB
62
Data in trailer (2)
method of identifying end of packet error checking
63
How packet switching works (3)
data split into packets each packet sent independently packets reassembled into correct order at destination based on information in header
64
Function of router (3)
stage in route receives data packet uses data in header to decide where to send it
65
Benefits of packet switching (2)
no need to tie up single communication line high transmission rate possible
66
Disadvantage of packet switching (2)
packets can be lost delay at destination where packets are re-ordered
67
Disadvantages of parallel data transmission (2)
skewed - data can arrive unsynchronised crosstalk - electrical interferences between wires can cause data errors
68
Wires which a USB consists of (2)
red and black for power white and green for data transmission
69
How USB connects to device (3)
computer automatically detects that device present USB loads appropriate device driver for communication new device detected = user prompted to download appropriate device driver software
70
Benefits of USBs (4)
devices automatically detected/loaded up can only fit one way preventing incorrect connections industry standard = considerable support available backwards compatible
71
Disadvantages of USB (3)
cable length only 5 m data transfer rate slow compared to others early USB models may not be supported by modern computers
72
How parity checks work (3)
parity is EVEN or ODD (number of 1 bits) left most bit is parity bit change = change in even or odd bits = error
73
How can parity checks not work
if there is an even number of bits changed
74
How checksum works (6)
checksum calculated from data block using algorithm checksum transmitted with data block checksum recalculated by receiver using same algorithm original checksum compared with calculated checksum checksum equal = no change if not = request to resend data
75
How echo checks work (3)
copy of data sent to receiver copy compared with original no difference = no error
76
Disadvantages of echo checks
not known whether error occurred when first sending data or when sending data back
77
What does ARQ stand for
Automatic Repeat Requests
78
How does ARQ work (5)
uses positive/negative acknowledgements check performed on data send acknowledgement that data received if acknowledgement not received = data resent in timeout until positive acknowledgment received or set number of retransmissions reached error detected = request to resend data
79
Define plaintext
original data being sent
80
How does symmetric encryption work
uses same key to encrypt/decrypt message
81
How encryption works (3)
plain text encrypted using algorithm/key key transmitted separately from text key used to decrypt the cypher text
82
Define cypher text
encrypted text
83
How does asymmetric encryption work (5)
uses private and public keys public key sent to sender sender encrypts document sender sends cipher text to receiver receiver uses private key to decrypt
84
2 types of MAC Addresses (2)
UAA - Universally Administered LAA - Locally Administered
85
What does an NIC stand for
network interface card
86
Function of an NIC
allow device to connect to network
87
2 version of IP
IPv6 IPv4
88
Advantage of IPv6 compared to IPv4 (3)
removes risk of IP address collisions has built-in authentication checks more efficient packet routes
89
Is an IP address always unique
no
90
Define static IP addresses (2)
permanently assigned to device by ISP do not change
91
Define dynamic IP address (2)
assigned by ISP when device logs on to internet change
92
Comparison between static IP address and dynamic address (4)
dynamic : more privacy since IP always change static : less privacy since IP can be tracked static : faster download speed static : more expensive
93
Function of routers (2)
enable data packets to be routed between different networks converts transmitted data to format understood by other network allowing them to communicate
94

Computer Science (15 decks)

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