others Flashcards
Define memory dump
when memory contents are output to printer/monitor
Uses of binary (3)
ASCII value
unicode value
machine code
Advantages of hexadecimal (5)
easier to understand
easier to debug
shorter = takes up less space
faster to enter than binary
easier to convert from binary than denary
Define simplex data transmission (2)
data transmitted one way only
e.g computer to printer
Define duplex data transmission (2)
data transmitted both ways simultaneously
e.g broadband internet
Define half-duplex data transmission (2)
data transmitted both ways not at same time
e.g walkie talkie
Define serial data transmission (2)
one bit sent at a time over one wire
e.g computer to printer/USB
Define parallel data transmission (2)
multiple bits sent at same time using multiple wires
e.g computer to modem/internal computer components
Advantages of serial (4)
reliable over longer distances
cheaper
data not out of synchronization
less risk of electrical interference between wires
Advantages of parallel (2)
faster transmission
easier to program input/output operations
Features of asynchronous data transmission (3)
data transmitted in agreed bit pattern
data bits grouped together and sent with control bits
receiver of data knows when data starts/ends
Features of synchronous data transmission (5)
continuous stream of data
data accompanied by timing signal
synchronizes sender and receiver
receiver counts number of bits sent
reassembles into bytes
Advantages of synchronous data transmission
faster
Define USB
data transmission method
What ASCII stands for
American Standard Code for Information Interchange
Number of bits in standard ASCII
7 bit codes
Function of ASCII
represent letter/number/characters on keyboard
Denary value for a on ASCII
97
Denary value for A on ASCII
65
Denary value for 0 on ASCII
48
ASCII disadvantages
does not represent non-western characters
Define unicode (2)
coding system
represents characters of all languages
How is sound represented digitally (4)
computer samples sound using ADC
amplitude determined at set time intervals
gives approximate sound representation
sound wave sample encoded as binary
Define sampling
measuring amplitude of sound wave
Define sampling resolution/bit depth
number of bits per sample
Define sampling rate (2)
number of sound samples taken per second
measured in hertz
Benefits of having larger sampling rate/resolution (3)
better sound quality
larger dynamic range
less sound distortion
Disadvantages of larger sampling rate/resolution (3)
larger file size
requires greater processing power
longer to download music files
How do bitmap images work (3)
made of pixels
each pixel represent binary number
binary numbers represent colour
Define colour depth
number of bits to represent each colour
Define image resolution
pixel number in an image
Photos with lower resolution will have higher detail than photos with higher resolution
True or False?
false
Disadvantage of using high resolution images (2)
file size increase
increase in download speed
Define a bit (2)
basic unit of computing memory storage
either 1 or 0
Number of bytes in kibibyte
2^10
Number of bytes in kilobyte
1000
Equation for file size of image
image resolution (pixels) x colour depth (bits)
Equation for size of mono sound file
sample rate (Hz) x sample resolution (bits) x sample length (seconds)
Uses of hexadecimal (4)
error codes
MAC address
IPv6 address
HTML colour codes
Hexadecimal use in error code
values refer to location of error
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
Define IP address
identifies global address on internet
Number of bits in IPv4
32 bits
Number of bits in IPv6
128 bits
Number of bits in MAC address
48/64
What does MAC address stand for
media access control
Use of HTML in hexadecimal (2)
represent text colors on screen
different intensity of primary colors determined by hex value
Hexadecimal red
FF 00 00
Hexadecimal green
00 FF 00
Hexadecimal Blue
00 00 FF
Why might one compress data (3)
reduce cost that come with larger file size
save storage space
reduce download time
2 types of file compression
Lossy
Lossless
Features of lossy file compression
eliminates unnecessary data
Lossy file compression examples (3)
Mp3
MP4
JPEG
Define mp3
lossy for audio files
Define mp4
lossy for multimedia files
Define lossless file compression
data from original file reconstructed
What does RLE stand for
run-length encoding
Structure of packet (3)
header
payload
trailer
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
Data in payload (2)
actual data
64 KiB
Data in trailer (2)
method of identifying end of packet
error checking
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
Function of router (3)
stage in route
receives data packet
uses data in header to decide where to send it
Benefits of packet switching (2)
no need to tie up single communication line
high transmission rate possible
Disadvantage of packet switching (2)
packets can be lost
delay at destination where packets are re-ordered
Disadvantages of parallel data transmission (2)
skewed - data can arrive unsynchronised
crosstalk - electrical interferences between wires can cause data errors
Wires which a USB consists of (2)
red and black for power
white and green for data transmission
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
Benefits of USBs (4)
devices automatically detected/loaded up
can only fit one way preventing incorrect connections
industry standard = considerable support available
backwards compatible
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
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
How can parity checks not work
if there is an even number of bits changed
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
How echo checks work (3)
copy of data sent to receiver
copy compared with original
no difference = no error
Disadvantages of echo checks
not known whether error occurred when first sending data or when sending data back
What does ARQ stand for
Automatic Repeat Requests
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
Define plaintext
original data being sent
How does symmetric encryption work
uses same key to encrypt/decrypt message
How encryption works (3)
plain text encrypted using algorithm/key
key transmitted separately from text
key used to decrypt the cypher text
Define cypher text
encrypted text
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
2 types of MAC Addresses (2)
UAA - Universally Administered
LAA - Locally Administered
What does an NIC stand for
network interface card
Function of an NIC
allow device to connect to network
2 version of IP
IPv6
IPv4
Advantage of IPv6 compared to IPv4 (3)
removes risk of IP address collisions
has built-in authentication checks
more efficient packet routes
Is an IP address always unique
no
Define static IP addresses (2)
permanently assigned to device by ISP
do not change
Define dynamic IP address (2)
assigned by ISP when device logs on to internet
change
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
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