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computer science > theory > Flashcards

theory Flashcards

1
Q

why do computers use binary

A
  • circuits in a computers processor are made up of billions of TRANSISTORS
  • a transistor is a tiny switch that is activated by the ELECTRONIC SIGNALS it receives
  • the digits 1/0 used in binary reflect the ON/OFF states of a transistor
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2
Q

units for data storage

A

1 bit b = 1/0
1 nibble = 4b
1 byte B = 8b
1 kilobyte kB = 1000B
1 megabyte MB = 1000kB
1 gigabyte GB = 1000MB
1 terabyte TB = 1000GB
Kites Make Great Toys

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3
Q

overflow error

A

error from attempting to represent a number thats too large for the registers available
eg biggest 8b number is 255 - so over 8b cant be represented

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4
Q

binary > decimal

A

place values
128, 64, 32, 16, 8, 4, 2, 1
eg 7 = 0000 0111

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5
Q

binary addition

A

1 + 0 = 1
1 + 1 = 0 carry 1
1 + 1 + 1 = 1 carry 1

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6
Q

hexadecimal uses

A

colour
MAC address

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7
Q

why humans use hexadecimal

A
  • simpler to remember
  • quicker to write/type
  • less likely to make errors (fewer digits)
  • easy to convert hex to binary
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8
Q

hexadecimal

A

base-16 number system
uses 0-9 and A-F to represent numbers from 0-15

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9
Q

hex > decimal

A

place values 16, 1
multiply left hand by 16 then add right hand
eg hex 37
= 16x3 +7
= 55

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10
Q

decimal > hex

A

divide by 16 to get left column
remainder = right column
eg 27
= 27/16 = 1r11
= hex 1B

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11
Q

binary > hex

A

splits into 2 nibbles of 4b
convert each nibble into hex using
8, 4, 2, 1 place values
eg 1110 0101
= 8+4+2= 14 4+1=5
= E5

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12
Q

hex > binary

A

split hex characters
convert into binary using 8, 4, 2, 1 place values
eg 3B
3 = 0011
B = 11 = 1011
= 0011 1011

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13
Q

binary left shift

A

x2^no. bits shifted

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14
Q

binary right shift

A

/2^no. bits shifted

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15
Q

standard ASCII

A

American Standard Code for Information Interchange
encodes 128 characters into 7b codes
includes 0-9, A-Z, a-z, punctuation

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16
Q

extended ASCII

A

encodes 256 characters into 8b codes
includes accents
1 character = 1B

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17
Q

limitations of standard ASCII

A
  • encodes 128 characters into 7b codes
  • only covers Latin alphabet
  • those who don’t use latin alphabet cant communicate eg Chinese, Greek, Arabic
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18
Q

advantages of ASCII

A
  • uses English language so it can store all alphanumeric characters
  • takes less space as it has only 128 characters
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19
Q

unicode

A

first 128 characters are the same as ASCII
unicode was developed to use 16b per character to represent 2^16 characters
can also use 32b per character to represent 2^32 characters

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20
Q

advantages of unicode

A

can represent more characters such as other alphabets and emojis
useful for global communication

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21
Q

disadvantage of unicode

A

uses up more storage / data

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22
Q

how pixels make up an image

A
  • make up bitmap images
  • each pixel is a single colour and given a binary value which represents that colour
  • the smaller the pixels the better the quality
  • a pixels colour can be changed by changing the binary value
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23
Q

pixel

A

smallest identifiable area of an image
make up bitmap images

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24
Q

resolution

A

concentration of pixels within a specific area
(area is defined by image width x height in pixels)
eg 72ppi is a typical screen resolution

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25
Q

colour or bit depth

A
  • no. bits used to represent each colour
  • higher bit depth = greater range of colour
  • a pixel is given a no. bits (n)
  • the no. combinations (2^n) dictates the bit depth and number of colours represented
    1b = 2 colours
    8 b = 2^8 colours
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26
Q

file size

A

resolution x bit depth
or height x width x bit depth
eg 20 x 20pixels and 8 colours
= 20 x 20 x 3 = 1200
higher resolution and bit depth = better quality but larger files

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27
Q

meta data

A

data about data
info other than the image data stored within a file
eg colour depth, resolution, date created, author

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27
Q

analogue sound

A

continuous waves
(one constant line)

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27
Q

digital sound

A

discrete waves
digitised by measuring and recording sound waves
(blocks at diff amplitudes)

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27
Q

analogue > digital converter

A

converts inputs to digital signals

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28
Q

sound sample

A

a measure of amplitude at a point in time
sampled using sample resolution (bit depth) and sampling rate

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29
Q

sampling rate

A

no. samples taken per second
1Hz - 1 sample per second
usually 44.1kHz
greater sample freq. = greater the accuracy + file size
(more samples = more bits)

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29
Q

sample resolution (b depth)

A

the no. bits used to record each measurement
increased bit depth = better quality (can represent more sound + height of wave is accurately measured) = greater file size
usually 16b = 2^16 values

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29
Q

file size of sound

A

sampling rate x sample resolution x duration (secs)

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29
Q

character set

A

a list of the characters and the binary codes used to represent each one
eg ASCII or UNICODE

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29
Q

compression

A

reducing the file size using an algorithm
used to:
- send files with smaller size
- store files with less storage (cheaper)
- send files faster
- reduce download size

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29
Q

lossy compression

A

removes info permanently
removes info less likely to be noticed by human eye
significant file size reduction can not be converted back

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29
Q

lossy compression eg

A

JPG
MP4
MP3
never text - would delete characters
can be used for video, music, photos

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29
Q

lossless compression

A

reduces file size sometimes
doesn’t loose any info
file can be converted back (data is restored exactly like it was originally)

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29
Q

lossless compression eg

A

PNG
PDF
GIF
TIFF
FLAC
can be used for images, text, music

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30
Q

lossless algorithms (2)

A

RLE - run length encoding
huffman trees

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31
Q

RLE

A

uses freq. / data pairs to encode
each run length of the same coloured pixel
eg 1 = - and 0 =.
-…- = 10001 = 11 30 11
useful on simple images not text (can increase file size)

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32
Q

huffman trees

A

analyse freq. that characters are used
characters are placed in binary tree structure with most frequent at top

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33
Q

how to work out file size reduction

A

original - new size / original

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34
Q

benefits of compression

A
  • smaller files = fewer packets = faster transmission (quicker + reduced traffic)
  • reduces download times (streaming possible)
  • images on web pages appear faster
  • reduces space on disk/ servers
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35
Q

boolean operators

A

NOT
OR
AND
XOR

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36
Q

truth tables

A

shows what happens if each combination of true / false is used

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37
Q

boolean logic

A

in which the answer is true or false (only 2 states)
1 = T
0 = F

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38
Q

AND logic gate

A

both conditions true = true
P = A AND B
P = A.B
=D-

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39
Q

NOT logic gate

A

condition is false = true
P = NOT A
P = Ā
=>-

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40
Q

OR logic gate

A

one or more conditions are true = true
P = A OR B
P = A+B
= )>-

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41
Q

XOR logic gate

A

only one condition is true = true
P = A XOR B
P = A ⊕ B
=))>-

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42
Q

hardware

A

The physical components that make up a computer system

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43
Q

software

A

non-physical programs that are stored by and run on a computer system

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44
Q

hardware eg

A

input - mic keyboard mouse
output -monitor speaker printer
storage - USB stick hard-drive

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45
Q

software eg

A

word processing software, instant messaging, email, operating system, web browser

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46
Q

computer system

A

combination of hard+ soft-ware working together
takes a set of digital inputs processes them and creates a set of outputs
input -> process (<->secondary storage) -> output

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47
Q

2 types of software

A

system
application
software -> system -> (OS or utility programs)
or -> application

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48
Q

system software

A

provides a platform for other softwares to work
e.g. OS or utility programs

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49
Q

application software

A

apps that allow use to perform tasks as the general user (play games, write essays)

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50
Q

operating system

A

processor management
storage management
memory management
input/ output device management
application management
security management
multitasking

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51
Q

application managment

A

controls access to apps the user instals
allows user to use authorised programs
allows user to install/uninstall apps
manages software updates
copies the program to and (allocates it to)an area of their RAM

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52
Q

memory management

A

-lets data be copied onto main memory
-keeps a record of where each program and data is (easy and fast to access)
- makes sure not to overwrite existing files

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53
Q

multitasking

A

Allows multiple tasks to run simultaneously (without would only ever be able to do one thing)
provides a task manager - can see what current task is taking up space / memory on the CPU (can then close this task to run efficiently)

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54
Q

peripherals

A

external components to a computer system e.g. keyboard

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55
Q

interrupts

A

signals sent to the CPU by external devices to indicate an event that needs immediate attention
e.g. mouse click ->response is opening document
- hardware interrupts - by hardware device e.g. printer out of paper
- software interrupts - by program - error message displayed

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56
Q

network

A

connection between 2 or more devices to share info / communicate

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57
Q

stand alone

A

not on a network can’t share or communicate with other devices

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58
Q

5 ways user managment is used on your schools network

A
  • provides and username/ password - only allows those authorised to access your files on school network
  • provides access rights - not all can access certain files or areas
  • secondary storage can’t be used / accessed so virus’ aren’t downloaded onto the network
  • users restricted from installing new software which prevents introduction of malware or software conflicts
  • settings/ profile managed by administrators
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59
Q

utility software

A

perform extra functionality + housekeeping tasks to keep computer running efficiently

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60
Q

utility software eg

A

encryption software
defragmentation software
data compression
disk clean up tools
anti- virus software

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61
Q

encryption software

A

used to encode text so cannot be understood without a key to decode it e.g. files/passwords

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62
Q

data compression software

A

makes files smaller in size
to reduce storage space and send files using less data

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63
Q

disk clean up tools

A

scans + finds files no longer needed
finds duplicate files
deletes and frees up space

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64
Q

anti virus software

A

detects harmful files from infecting devices with malware
warns + informs of dangers
(prevents getting virus)
quarantines + removes virus
can’t fix harm caused by virus

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65
Q

disk defragmentation software

A

reorganised files so they are stored together
read faster and new files don’t need to be fragmented

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66
Q

embedded system

A

A computer system with one dedicated task ( no multitasking)
built into a physical device
e.g. camera, microwave, washing machine, card reader, toaster, oven, traffic light

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67
Q

what is a programming language

A

used to give a series of instructions to devices to perform a specific task

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68
Q

two levels of programming languages

A

low-level e.g. machine code assembly language
high-level e.g.python, Java

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69
Q

macine code

A

binary instructions (1,0) slow and inefficient what the computer understands
each processor only understands its own type of machine code - can’t use apple apps on a samsung (diff processor types)

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70
Q

assembly language

A

allows the programmer to create programs easily
uses mnemonics and simple instructions to get the machine to do something
shorter and easier to understand
processor specific
used for embedded systems

71
Q

assembler

A

translates assembly language into machine code

72
Q

high level languages

A

use statements close to English or maths making it easy to write programs to solve problems
it is machine independent so can work on other devices
translated into machine code by a compiler or interpreter

73
Q

+ of high level languages

A

Machine independent
easier to understand
easier to debug
easier to learn and written faster

74
Q
  • of low level languages
A

not machine independent
hard to understand
hard to debug

75
Q

+ of low level languages

A

can run quickly
require less memory
statements in low-level languages can control specific hardware

76
Q

2 types of translator for high level languages

A

interpreter
complier

77
Q

interpreter

A
  • translate and runs one line at a time
  • Has no output as it runs the program straight away
  • slow to run as is translated every time it’s run
  • user need an interpreter installed
  • user can see and copy the source code
  • used for program development
    e.g. python idle
78
Q

compiler

A
  • translates whole program to execute later
  • outputs object code (machine code) which can be used later
  • Run fast as it is already in the machine code
  • user does not need a compiler installed to run software
  • user cannot see the source code when distributed
  • used for software that is run frequently or sold to third party
79
Q

computer system

A

sores/ processes a set of inputs producing an output

80
Q

CPU

A

Processes instructions
brains of the computer runs one simple instruction at a time
can run billions instructions per second
collects instructions from RAM and sends data back to RAM for storage (fetch decode execute cycle)

81
Q

stored program concept

A

The idea of storing the program instructions as well as the data in the memory (von Neumann architecture)

82
Q

parts of the CPU

A

control unit
ALU
register
cache

83
Q

control unit

A

controls and coordinates activities taking place in the CPU
decode and executes
receives signals

84
Q

ALU

A

performs operations on data
arithmetic operations (maths) and logical operations (comparing data)

85
Q

registers

A

Store small amounts of data + results the CPU is currently working on
temporary storage is emptied once a CPU is finished and sends data to RAM

86
Q

cache definition

A

stores data or instructions that are most commonly used so is faster to access

87
Q

clock speed (processor speed)

A

Number of clock cycles per second (Hz)
1 cycle per sec = 1Hz = 1 instruction
todays CPU have a clock speed of 3.6GHz which is 3.6 bill cycles per sec

88
Q

buses

A

set of parallel wires connecting two or more components of a computer
system bus is made of three types address bus, data bus, control bus
CPU is also connected to external devices by buses
can be one directional or bidirectional

89
Q

control bus

A

Send signals between devices to ensure the correct devices are communicating
insures instruction data received and sent to correct location
BIDIRECTIONAL

90
Q

address bus

A

stores the address/location of the memory slot where the instruction need to be collected from and data stored
ONE DIRECTION

91
Q

data bus

A

carries data/instructions throughout the computer system
BIDIRECTIONAL

92
Q

3 factors affect CPU performance

A

clock speed
processor cores
cache

93
Q

multi-core processor (no. processors)

A

dual core has two processors
potential to perform two instructions at once
A dual core processor of 1 GHz means 2 1GHz processors which is 2 GHz

94
Q

why dual processors dont always perform 2 instructions at once

A

Software can’t take full advantage of two cores (sequential processing)
parallel processing - programs can be run simultaneously split between different cores (multi core is better)
sequential processing - programs run in sequence so can we only processed by one core (single core is fine)

95
Q

cache memory

A

A small amount of fast expensive memory in the CPU
can be accessed faster than RAM
stores recently/frequently used data
Level one - small but fastest located on the CPU
level two - fast but slower than ever one but more data - given to each core
level 3 - slowest but most storage faster than ram

96
Q

fetch decode execute cycle

A

Fetch
-The control unit reads the memory address of the next instruction
-the instruction is copied from memory to one of the registers in the CPU
Decode
-the control unit decodes the instruction to work out what it is so it can be executed
Execute
-the instruction is carried out-data may be read from/written to RAM

97
Q

memory

A

stores inputs / outputs
for a computer to work efficiently

98
Q

storage

A

User stores files and information
nonvolatile long-term permanent

99
Q

motherboard

A

ROM
RAM
CPU
hard disk drive

100
Q

when device is switched off

A

Only ROM and hard disk drive store data ROM permanently stores instructions for device start-up (bootstrap)
hard drive permanently stores OS apps installed and files

101
Q

when device is switched on

A

CPU wakes up and starts to process data from the start up instructions it receives from ROM
then the
Hardrive sends instruction to load OS to RAM which sends to CPU
than CPU loads OS which was stored in the hard drive
(fetch decode execute begins to happen constantly)

102
Q

when the user turns off the device

A

RAM clears all contents so computer is fast when used again
hard disk keeps all existing apps and files stored and saves any new apps or files
ROM retains start up instructions ready to use (never deleted)
CPU go to sleep

103
Q

2 types of primary memory

A

RAM
ROM

104
Q

RAM

A

DATA AND INSTRUCTIONS IN USE
Volatile (data doesn’t stay clear when powered off)
can write from and written to
fast access and hard drive
Stores: OS part in use, software in use, data software is using

105
Q

hard drive

A

stores OS permanently
nonvolatile (doesn’t lose data powered off)
typically 1- 3 TB
Slow to access and hard to locate data cheaper

106
Q

why does data / OS load to RAM

A

hard drive is further and slower to access
has lots of unused data stored so it’s hard to locate data
reading/writing is slower

107
Q

virtual memory

A

when RAM gets full a section of the hard drive starts working as RAN

108
Q

ROM

A

Used to store data
Read only
Nonvolatile
Stores
- bootstrap - initial program run when computer is turned on
- BIOS - controls basic tech config of computer ( processor speed, system time)

109
Q

purpose of CPU (4)

A

-processes data and instructions
-brain of the computer
-runs on instruction at a time (runs billions per second)
-collects instructions from RAM and sends data back to RAM (fetch decode execute)

110
Q

fetch (2)

A

-control unit reads memory address of instruction
-insturction is copied from memory into CPU registers

111
Q

decode (1)

A

-control unit decodes instruction to work out what it is and what to do

112
Q

execute

A
  • instruction carried out
113
Q

what does teh ALU do (2)

A
  • performs arithmetic operations -+x/
  • performs logical operations AND OR < =
114
Q

emmbeded system (2)

A

-a computer with a specific single purpose
-built into a physical device
(held in non volitile memory)

115
Q

embeded system eg

A

microwave
oven
traffic light
washing machine
camera

116
Q

RAM vs ROM (4)

A

ROM-nonvolitle ~ RAM-volitile
ROM-read only ~ RAM-read/write from/to
ROM-cheaper ~ RAM-expensive
ROM-stores bootstrap +BIOS ~ RAM-stores data/OS/instruction in use currently

117
Q

whats held in RAM

A

OS part in use
software in use
data software is using

118
Q

factors that affect CPU performance

A
  • no. cores
  • cache size
  • clock speed
119
Q

cache

A
  • more cache means more frequently used data is stored near the CPU
  • the means its faster to access rather than fetching it from RAM
  • level1 cache means its closer so is fastest to be accessd
120
Q

clock speed

A
  • determins number of cycles per sec (Hz)
  • 1Hz = 1 cycle per sec = 1 instructions per sec
  • faster speed = more instructions carried oht and a faster comouter
121
Q

no. processor cores

A
  • multiple cores means the POTENTIAL to perform two instructions at once
  • (sequential processing cant take advantage of multiple cores)
  • more cores = more instructions at once = fater procsessing
122
Q

storage method 3

A

magnetic
optical
solid state

123
Q

magnetic storage 4

A

HDD/magnetic tape
- has platters
- that spin
- has read/write arm
- magnetic field determines binary value

124
Q

magnetic storage +3/ -4

A

+ large storage
+ cheap
+ fast read/write
- lots of parts
- not durable
- sealed unit ( cant fix easily)
- not portable

125
Q

optical storage 4

A

CD/ DVD/ BluRay
- is a disk
- binary represtented using pits/lands
- laser shines on - pits reflect light differently to determine binary value (read)
- laser makes indents on disk (write)

126
Q

optical storage +3/ -2

A

+ cheapest
+ portable
+ small
- less storage
- easily scratched

127
Q

solid state storage 3

A

SSD
- sends current which forces electrons through a barrier
- and traps them in floating gates
- binary data is stored by the held electrons
(flash memory)

128
Q

solid state +5 / -1

A

+ no moving parts (durable
+ fastest read/write
+ fast start up
+ quiet
+ don’t need to defrag
- expensive

129
Q

ssd vs hdd

A
  • hdd moving parts (less durable)
  • hdd slower to read/write
  • ssd less long read/write life
  • ssd expensive + less data
130
Q

cloud storage4

A
  • storing data in an off site storage system online
  • files send to sever connected to internet and maintained by a third party
  • servers use hdd/ssd
  • data accessed via internet
131
Q

computer network 2

A

2 or more connected computers
to communicate transmit exchange or share data/ resources (files/printers)

132
Q

stand alone

A

not connected to a network

133
Q

internet 3

A

group of interconnected networks
collective ownership
services use it (web, mail)

134
Q

world wide web 4

A

uses internet
information system of linked web pages
accessed via web browser
uses HTTP to send / retrieve data

135
Q

WAN 4

A

Wide Area Network
- networks in diff geographical location
- networks connected so computers can communicate uses resources supplied by 3rd party - BT
- uses cables satellites or radio waves
- internet is largest wan

136
Q

IP address

A
  • given to devices by network
  • identifies devices on network
  • routes packets to destination
  • can change depending on location
    e.g. 72.129.214.16
137
Q

data packets

A

data broken into small pieces to be transmitted
contains:
- sender/receiver IP address
- packet no.
- no. packets
- actual data/message
flow through diff internet routes (prevent traffic)
put together at end in order

138
Q

NIC 2

A

Network Interface Card
- allows communication between devices
- in every networked device

139
Q

MAC address 3

A

Media Access Control address
- assigned to NIC
- never changes
- routers use to send packets
e.g. 3B:14:E6 - it’s in hex

140
Q

router

A

looks at packet destination and sends to network close to destination

141
Q

switch

A

connects nodes
seds packet to correct computer

142
Q

wireless connection 3

A
  • broadcasts radio waves to communicate
  • connect via WiFi
  • susceptible to interference
143
Q

WAP

A

Wireless Access Point
- allows wireless devices to join network

144
Q

wired connection

A

ethernet cables

145
Q

wireless 3+

A
  • no cables
  • easy to connect new devices
  • can have portable devices
146
Q

wireless -5

A
  • less reliable
  • if many devices use th WAP connection is slow
  • speed is slow far from WAP
  • less secure
  • affected by interference e.g. furniture
147
Q

fundamental network hardware

A

cables (ethernet)
switch
router
WAP

148
Q

LAN 2

A

Local Area Network
- operates on single location
- have own cabling system to a switch

149
Q

network 3+

A
  • share data / resources
  • any device can accessed files saved centrally
  • back up easy as files are stored on servers
150
Q

network 3-

A
  • expensive hardware
  • management is complicated (have to employ maintenance people)
  • malware can infiltrate network and all computers
151
Q

topology

A

the way system parts are connected

152
Q

star topology

A

all connected to central switch/ hub

153
Q

bus topology

A

all connected to main cable (bus)

154
Q

bus 3+ 3-

A

+ less cable (cheaper)
+ easily add devices
+ if central switch fails the whole network doesn’t go down
- Single cable shared by all devices so many collisions (slow)
- if this cable is damaged whole network fails
- any device can view all data on the cable - bad security

155
Q

star 3+ 3-

A

+fast data transfer
+ if one cable fails other cables not affected
+ Devices can’t view other devices data
- requires hardware - switch
- if switch fails whole network is down
- harder to add more devices

156
Q

ethernet

A

Standard local networking rules
describes how devices format data for transmission
E.G. copper coaxial and fibre-optic

157
Q

do computers transmit data simultaneousely

A

Computers wait till the quiet connection before transmitting data - no traffic

158
Q

copper cable

A

+ CHEAP
- adequate speed - for low bandwidth
- affected by electrical interference
- loss of signal over distance

159
Q

fibre optic cable

A

+ FAST - greater bandwidth
+ FAR - less affected by distance
+ signals travel by light waves - so not affected by emag. signals
- higher cost for cabling

160
Q

PAN

A

Personal Area Network
- connects computer devices near a person
- via Bluetooth

161
Q

bluetooth

A
  • wirelessly can connect devices over short distance
  • uses radio waves
  • MAC address used to pair devices
162
Q

network security methods

A

authentication
encryption
firewall
MAC address filtering

163
Q

authentication

A

Checking the user is allowed to access content
E.G.password biometrics two factor authentication pin pattern

164
Q

encryption

A

data can be intercepted - encryption prevents the data from being interpreted
- HtTps:// means it’s secure
Encoding data using an
algorithm so it cannot be understood

165
Q

symmetric encryption

A

same key used to encrypt/decrypt data
Key is private and given to the recipient

166
Q

asymmetric encryption

A

two key (public+private) is used to decrypt more secure as the private key is never sent

167
Q

firewall

A

Separates a trusted an untrusted network
Can be hard or software
packet filter - packets are checked to see where it’s coming from or going to packets that don’t match the rules are dropped

168
Q

firewall features 5

A
  • monitors packets in/out of network
  • can allow/block traffic based on security rules
  • prevent an attacker getting access to the network
  • filter IP address - blocks malicious websites
  • port blocking - prevent access to ports on a network
169
Q

MAC address filtering

A
  • can block access devices identified by Mac addresses
  • MAC address never changes I need to find the device at manufacture
170
Q

protocol

A

set of rules

171
Q

server

A

computer program/device that provides a service to another computer program + user (or the client)

172
Q

HTTP

A

hypertext transfer protocol
for accessing + recieving web pages via. Internet (written in HTML)
the protocol requests a web page from the web server
(the server sends its response containing the web page)

173
Q

HTTPS

A

secure HTTP
encrypts info so it cant be understood
used by banks, online shops, social networks - for personal data

174
Q

FTP

A

file transfer protocol
used for sending/ retrieving files to/from a server

175
Q

SMTP

A

outgoing
email software sends to the server
server relays the message via mail relays
email arrives at destination server

176
Q

POP/ IMAP incoming

A

fetch message data from remote server

177
Q

POP

A

Post Office Protocol
downloads new message to local device (no longer on server)

178
Q

IMAP

A

Internet Message Access Protocol
leaves messages on server
can be accessed by many devices
removed if user deletes them

179
Q

email

A
  • sent using SMTP to local server
  • local server forwards to remote webmail server
  • stored on webmail server
  • can be accessed by POP/IMAP
180
Q

TCP

A

Transmission Control Protocol
- breaks up messages into packets
- reassembles packets
- detects errors
- resends lost messages

181
Q

IP

A

Internet Protocol
- routes packets from one IP address to another

182
Q

protocol stack

A

defines 4 layers enabling communication on the internet
(modular design each layers responsible for a part in the communication process)
- application layer
- transport layer
- internet layer
- link layer

183
Q

sending

A

the app used to send decides the protocol used
- computer app produces data to send
- data split into packets
- data sent + routed
- physical hardwire + cables

184
Q

application layer

A

apps create data to send in this layer
SMTP - email
FTP - upload files to website
HTTPS - banking

185
Q

transport layer

A

creates connection between 2 computers (hosts)
- agree on communication settings + packet size
- data divided into packets
- packets reassembled by recipient
- lost packets resent
(TCP, UDP)

186
Q

internet layer

A

routes packets (uses routers)
source and destination address written on packets for transmission (IP)

187
Q

link layer

A

physical hardware located here: NIC, cables/WIFI, device drivers
(MAC , ethernet, WiFI)

188
Q

recieving

A

data packets move back up layers
- link removes MAC address
- internet layer removes IP address
- transport layer reassembles packets
- application layer uses correct protocol to display data, web page or email

189
Q

layers +

A

self contained
- functionality can be changed without affecting other layers

diff hard/software operates on a layer providing interoperability between providers/systems
- manufacturers routers operating on the Internet layer can operate with another manufacturers NICs on the link layer
- senders and receivers using diff soft/hardware can communicate using same layer protocol

190
Q

UDP

A

User Datagram Protocol
maintains open data connection to send a stream of packets without checking they’re received correctly - UNRELIABLE
(online gaming, video streaming)

computer science (13 decks)

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