1
Q
Logic Gates
A
OR )> AND |) NOT |>º NOR )>º NAND |)º XOR ) )>
2
Q
Truth Tables
A
Truth tables are compiled in numerical order
OR: A OFF , B OFF = 0 A OFF , B ON = 1 A ON , B OFF = 1 A ON , B ON = 1
AND: A OFF , B OFF = 0 A OFF , B ON = 0 A ON , B OFF = 0 A ON , B ON = 1
NOT:
A OFF = 1
A ON = 0
NOR: A OFF , B OFF = 1 A OFF , B ON = 0 A ON , B OFF = 0 A ON , B ON = 0
NAND: A OFF , B OFF = 1 A OFF , B ON = 1 A ON , B OFF = 1 A ON , B ON = 0
XOR: A OFF , B OFF = 0 A OFF , B ON = 1 A ON , B OFF = 1 A ON , B ON = 0
3
Q
Logic Statements
A
Writing a logic statement, steps:
- X (or other) =
- final logic gate in the middle
- brackets on either side of gate in the middle
- logic gate in middle of either bracket for both sides and continue working backwards
4
Q
Logic circuits
A
From information or logic statement, work from middle gate and place last and continue working from middle till done.
5
Q
Computer Architecture
A
Stored program concept (Von Neumann Architecture)
- single processor in computer system
- processor uses sequential fetch-execute cycle
- data (files) and instructions (software) both stored in same memory (RAM)
Prior to this if a computer wanted to carry out another task it would have to be physically rewired
6
Q
Processor Cycle
A
Main stages of the processor’s cycle
- Fetch - the instruction
- Decode - the instruction
- Execute - the instruction
7
Q
Parts of a processor
A
Memory Unit:
- temporary storage areas for data and instructions
- inside the processor (not within RAM)
Arithmetic-Logic Unit (ALU):
- carries out mathematical equations on data
- evaluates relational comparisons
- inside the ALU is a general-purpose register called the accumulator (data needs to be placed in the accumulator for calculations to be carried out by the ALU)
Control unit:
- co-ordinates what and where data goes when it enters or leaves the processor
- it also controls the interactions between the different parts of the processor (e.g. the registers)
IAS/Immediate Access Memory (Cache memory):
A processor also has built-in cache memory. This is super-fast memory (much faster than RAM) that is stored within the processor.
8
Q
Parts of Processor (Image structure)
Processor image (3 images)
A
Refer to IG Computer Science OneNote for answer
OneNote > Content Library > Unit 3 > Parts of a Processor
9
Q
What is a register
A
A temporary memory location within the processor.
Registers store data and instructions whilst they are being processed.
Registers are also used to move data and instructions into and around the different parts of the CPU.
10
Q
Special types of Registers
A
MAR - memory address register
Contains the location in RAM of the current instruction being processed
MDR - memory data register
Contains the contents (values, instruction) returned from RAM
CIR - current instruction register
Contains a copy of the contents of the MDR
Responsible for decoding the instruction
PC - program counter The location (memory address) in RAM of the next instruction to be fetched
11
Q
General Purpose Register
A
ACC (accumulator) - stored in ALU
Keeps track of data that needs to be accessed over a period of time during processing
12
Q
Buses
A
Buses are wires used to transmit data within the processor and on the motherboard.
Three types of buses:
Address bus
- used by PC and MAR to transmit locations in RAM (i.e. addresses)
Control bus
- used by the PC and the MDR to send instructions
Data Bus
- used to carry data between RAM and the MDR, and between the MDR and the CIR
13
Q
Stages in the fetch-execute cycle
A
Fetch execute cycle steps
- PC has address of next instruction
- PC copied to the MAR
- Lookup MAR and get contents. Copy contents into the MDR
- Copy MDR contents into the CIR
- PC is then incremented by 1
- The instruction is decoded and then executed
- Repeat
14
Q
Input devices - 2D scanners
How a 2D scanner works:
How a (_____) works:
OCR:
A
An input device digitised by a scanning device such as flatbed or barcode scanner.
How a 2D scanner works:
- Scanner shines a light beam onto document.
- Scanner detects level of reflected light from positions on the document.
- Light intensity is converted by software for each pixel position into a combination of 0s and 1s by sensing different intensities of light and dark from the document.
How a flatbed works:
- Place document - raise cover, put document on panel and close
- Very bright light - (xenon lamp)
- Scan head - moves across the document and image is created and sent to a lens using mirrors
- Charge Couple Device - focused image falls on CDD, IC’s etched into silicon and software produces digital image
OCR Optical character recognition: OCR alongside 2D scanner used in airport for passport to face identification eg. Distance between the eyes Width of the nose Shape of the cheek bones Length of the jaw line Shape of the eyebrows
15
Q
Input devices - Linear Barcodes
A
Linear Barcodes are 1D and the most commonly used
Steps:
- Infra-red laser light shines onto linear barcode.
- Light reflected back into the moving mirrors/prism
- The barcode reader’s charge-coupled device (CCD) measures the amount of reflected light input.
- Light measurement is converted into an electrical charge (1 or 0).
- Data from the bar code is sent to the computer’s processor in binary form.
16
Q
Input devices - QR Codes
A
Quick response codes are faster to read and have a greater storage capacity than UPC linear barcodes.
Scanned digitally by phone’s image sensor then interpreted by microprocessor.
17
Q
Input devices - Keyboards
A
Keyboard works using plungers at the bottom of each key which when pressed pushes 2 electrical contains completing a circuit (key matrix).
Key matrix (circuits) stored in ROM
18
Q
Input devices - Mouses
A
Trackerball Mouse:
- Similar to the concept of the original mouse but upside down. The movement of the ball in the socket contains sensors. The data from the sensors processed by a software determines the movement of the pointer.
Optical Mouse:
- A red LED bounces light off the surface onto a CMOS sensor which sends each image to the DSP for processing. The DSP detects if the mouse has moved, at what distance and at what speed.
19
Q
Input devices - Microphones
A
All microphones need to input a varying pressure wave and then convert this to an electrical reading.
- Sound vibration hits a diaphragm.
- Movement of the diaphragm causes a coil to move.
- Movement of the coil induces a current through the electromagnetic effect.
- The electrical current is digitised (ADC - analogue-digital converter)
- The digital content is played back using software.
20
Q
Sensors - Light, Temperature, Pressure, Motion, Gas, pH, thermal, moisture, humidity
A
Light:
Light Sensors are photoelectric devices that convert light energy (photons) into an electrical (electrons) signal
eg. barcode scanner, automatic lights as it gets dark
Temperature:
A temperature sensor is a device, typically, a thermocouple or RTD, that provides for temperature measurement through an electrical signal.
eg. thermometer
Pressure:
A Pressure sensor measures the amount of force exerted.
eg. old-style electric doors, pressure inside gas canisters
21
Q
Primary/Main Memory/Storage
A
All computers must use Primary storage and it is directly accessible by the processor because it is connected directly to the motherboard.
- RAM random access memory
RAM is volatile and directly connected to the CPU.
22
Q
RAM
A
RAM stores data and instructions that are currently open and running. If a file or program is not open, it will not be in RAM.
RAM contains parts of the operating system that are currently in use. Contents stored in RAM are directly accessible to the processor. When you load a stored file it is first loaded into RAM before any changes made to the file are processed by the CPU.
RAM is volatile so when power to the computer system is lost so are the contents of RAM.
Storage capacity is in GB and has read and write ability.
Its contents change every time we use a computer.
23
Q
ROM
A
ROM stores your computer system’s BIOS and bootstrap loader.
Basic Input Output System (BIOS)
Most do not need to access the BIOS on a regular basis, if at all. The BIOS allows us to change things like the bootable drive.
Bootstrap loader
When you first turn on (‘boot’) your computer, the operating system has not yet loaded.
Your computer performs a self check of its hardware. It makes sure that it recognises it has RAM and a bootable drive of some sort.
ROM is non-volatile memory between 4-8 MB storage
24
Q
Secondary Memory/Storage
Types
Use in a laptop or computer
What it is
A
Magnetic/Solid state/ off-line
A laptop or desk top computer either has an (HDD) or an (SSD) as its main secondary memory/storage device.
Secondary storage devices are not directly accessed via the processor. Their contents are first be loaded into RAM before being transferred to the CPU for processing.
25
How HDDs work
An HDD platter is magnetic
the film stores data (bits)
bits are written to using the magnetic read/write head
the positive or negative charge (polarity) is different for a 1 and 0
26
SSD
```
SSDs are non-volatile storage devices
No moving parts
Uses flashing light to store data on chips
Solid state external device
Large storage capacity
```
27
HDD vs SSD
HDD:
- cheaper
- longer lifespan
- larger storage capacity
SDD:
- uses less power
- skinny compact
- no delay when reading or writing data
- less heat produced
- quieter
- more durable (harder to break)
28
Secondary storage device Types and examples
Magnetic:
- Magnetic tape
- Floppy discs/drives
- HDD
Optical:
- CDs
- DVDs
- Blu-ray
- DVD-RAM
Solid state:
- SSDs
- USB Flash memory/memory sticks
- SD cards
29
Offline storage
| Types and examples
Offline storage is external to the computer system and can be taken away from the computer.
Magnetic:
- external HDD
Optical:
- CD
- DVD
- Blu-ray
Solid state:
- external SSD
- memory stick (not USB on it's own)
- SD cards
30
How a CD works
Data is stored on the CD on a single spiral track in pits (0s) and lands (1s).
The CD drive spins the CD at a constant speed.
A red laser shines on the CD's surface.
Light is reflected from the disc from the pits and lands, which is how binary data is read from the CD.
31
Primary storage vs. Secondary Storage
Types
Volatility
Contents
Placement
Read/Write access speeds
Relationship to CPU
Primary Storage:
RAM - volatile, ROM - non-volatile
RAM - currently running programs and files, ROM - BIOS and bootstrap loader (start-up instructions)
Internal placement
RAM - plugged onto motherboard
ROM - soldered onto motherboard
Faster than secondary storage
Directly accessible by the processor (CPU)
Data and instructions must be in RAM before being sent to the CPU for processing
CPU loads the operating system when the bootstrap loader in ROM runs when the computer is turned on
Secondary Storage:
HDD, SSD
Both are non-volatile
Both - stores files and programs for long-term storage
Internal and external options
Inside computer case, attached to motherboard via cable
Portable HDD or SSD, connected via USB port
Slower than primary storage
Contents are not directly accessible by the processor (CPU)
Data and instructions on HDD and SSD (internal and external) is loaded into RAM first
32
Blu-ray vs. DVD
DVD red laser
| Blu-ray blue laser and more storage
33
DVD vs. DVD-RAM
DVD read only and one spiral track
| DVD-RAM read and write (at same time too) and multiple concentric tracks
34
Flash memory vs. CD-RWs
Type of offline storage media
How data is read/written
Read/write access speed
Hardware
Flash memory:
solid state
transistors/logic gates
faster than CD-RW because no moving parts
plugs directly into computer via USB port
```
CD-RW:
optical
red laser
slower than flash memory
requires a separate CD drive to read or write data
```
35
Output devices - Inkjet printer
They operate by heating the ink as it flows through a set of tiny nozzles. The heating process causes a small droplet of ink to form. This is then released as a single dot which forms part of a letter or image.
Either thermal uses heating element to make air bubble
or piezoelectric crystal to vibrate
adv. Cheap, compact, faster than dot matrix, quiet
disadv. colour is slow, wet ink can smudge
36
Output devices - Laser printer
Laser printers used the same technology as photocopiers.
(Image refer to laser printer image in OneNote)
1. Laser beam and rotating mirror used to draw image of page on drum.
2. Image converted on drum into electrostatic charge, this attracts and holds toner.
3. Charged paper rolls against the drum.
4. Charge pulls the toner away from drum and onto paper.
5. Heat fuses the toner to the paper.
6. The electrical charge is removed from the drum and the excess toner is collected.
NB - for multiple colours, multiple drums
37
Output devices - Dot matrix printer
Comparatively noisy and low quality but cheap to run and used when carbon copies or duplicates are needed. Useful in dirty environments such as a garage because they are very sturdy.
38
Output devices - 3D printer
3D printers use an additive printing process, using melted layers of plastic (filament) to create 3D objects.
A 3D printer builds up an object from adding more and more layers of material usually PLA.
39
Output devices - Speaker
A loudspeaker takes an electrical signal and translates it into physical vibrations to create sound waves. The speaker is carrying out the exact reversal of what is done by a microphone.
Main components are a voice coil, diaphragm and magnetic.
40
Output devices - Flat panel display screen (LCD & LED)
LCD Technology
LED Technology
LCD v LED
Liquid Crystal Display (LCD)
- Uses light modulating properties of liquid crystals
1. The screen comprises individual red, green and blue (RGB) pixels that are organised into small blocks.
2. Each 'block' is made of liquid crystals (hence the name, LCD!)
3. When the electric current being sent to the block of liquid crystals changes it causes the pixels to also change by turning solid or transparent.
Light-Emitting Diodes (LED) Display
- Uses an array of light-emitting diodes as pixels
LEDs use the same technology as LCDs to create an image
```
LCD advantages:
less power
low manufacturing cost
LED advantages:
no added light sources needed
works well in very hot or cold temps
fast
doesn't need an AC drive
```
41
Output devices - Touch screens
(Refer to OneNote for images)
Capacitive:
Made up of an insulating layer of glass that is coated with transparent conductive material. When an area of the screen is touched the voltage drops there. The processor uses the change in the electrical field to calculate where the screen was touched. (refer to OneNote for image)
Resistive:
Made up of two separate layers, bottom glass top plastic. When touched the two layers meet and this sends a signal to the processor, which uses the coordinates of the screen to calculate where it was touched.
Infra-red:
Screen is made of glass and requires human input for touch, if touched in multiple places the location can't be determined. Works with matrix of IR beams like lasers in spy movie.
42
Output devices - Projectors
Liquid Crystal Display (LCD) projectors:
sharper/better image quality
Quieter
pixels are more visible
uses less power and runs cooler than a DLP projector
projects light through three prisms (RGB)
three lights (RGB) merge when they pass through a fourth prism to display an image onto a large screen
Lamp > separation prism > colour filter > combining prism > lens = image
Digital Light Projectors (DLP) :
lighter, more portable
produces 'blacker blacks'
often more expensive than regular LCD projectors
uses a thousands of micro mirrors (built onto on integrated circuit (chip)) to project an image onto a large screen
Lamp > condensing lens > colour filter > shaping lens > DMD > lens = image
43
Operating systems
An operating system is a collection of programs that form the basis of the main system software found in a computer system. An operating system provides a platform for application software to be installed.
44
Interrupts
An interrupt is an electronic signal from hardware or software that requests the processor's attention.
An operating system contains a program called an interrupt handler. The role of the interrupt handler is to prioritise the interrupt signals as it receives them and places them in a queue to be handled.
Interrupts can be hard or software based, are handled by the operating system, allow a computer to multitask, does not work out priority and a computer cannot function without interrupts.
–––––––––––––––––––––––––
Interrupts are signals sent to the CPU by external devices to indicate that an event needs immediate attention
They tell the CPU to stop what it is currently doing and give priority to the interrupt
Hardware interrupts are generated by hardware devices eg. printer out of paper
Software interrupts generated by programs
eg. divide by zero
45
Software
Software Categories
Software types
Categories:
System software, Application software
System software:
Programs that are needed to run the computer eg. windows
Application software:
Programs that are needed to perform tasks for the user
Free software, freeware, shareware:
Most commercial software has to be paid for
Using an unlicensed copy of software is a copyright infringement and is illegal
Some software is free of charge and allows users to study, modify and distribute it
46
Free software
Free software is software that comes with permission to use, copy and distribute it with modification either gratis or for a fee
47
Open source software
Open source software is free of charge and the source code is given to a user to use in any way they like
48
Freeware
Freeware may be used without payment it may permit redistribution but not modification as the source code is not available.
Examples:
- Google chrome
- Skype
- Adobe reader
49
Shareware
A software that is initially free on a trial basis
The software is copyright and after trial must be paid for, the source code is not available and it can not be modified but is often encouraged to be made copies of and shared to help distribute it.
50
Operating Systems
System software types
Examples of OS
Definition and function
System software:
Operating systems
Utility programs
Program translators
```
Examples:
IOS
Android
OS X
Windows
Google chrome
Linux
```
Definition and function:
Software that manages a computer's hardware and provides a user interface
Also provides security
51
User interface
mini def
Types x 6
Without user interface we would communicate in binary
Types:
GUI , graphical user interface; most commonly associated
Menu-driven interface; music players and ATM machines
CLI, command line interface; all user commands types in as text and no graphics, uses less space on disk and RAM
Voice activated
Real-time
Windows; WIMP - Windows, Icons, Menus and Pointers; user can click on icons using a pointer or cursor and right click to display a menu
52
How computers handle Memory Management
Data used by the computer is copied into main memory
The operating systems keeps a record of where each program and its data are located
It must not overwrite pre-existing programs
53
Multi-Tasking
When running multiple programs on a computer,
the programs in the background running are taking turns to get processor time to execute instructions
The OS Manages how the programs share the processor
Task manager
54
Peripheral management
Peripherals are all the devices outside of the CPU, input/output devices and secondary storage, access speed of these is relatively slow
55
Print buffer
Status of each job on a printer screen displaying whether it is printing or waiting to print
56
Storage device and disk file management
who manages and what they do
def
OS manages:
- Copying files from disk to main memory
- Copying data files back to secondary storage
Hard disk in computer is a storage peripheral:
OS manages where on disk files are written, keep track of their location to be fetched, making sure no file overwrites another file
57
Managing Security
who does and how do they
OS organises user logins and passwords which may include password protection and control access rights
58
Access rights
If a computer is used by more than one user, each user should only be able to see their own files. Users and system admin have different levels of access rights. Some users may be allowed to access files but not edit them.
May include encryption of some files
59
Machine code
Computers represent everything in binary
Program instructions once converted to binary are known as machine code, eg.
1001 1100 0000 1110 1101 1010 1101 1011 0101 1001
Each different type of processor has its own set of machine code instructions, a typical instruction in a simple processor may look like:
Opcode: 6 digits, 010110
Register: 2 digits, 01
Operand: 8 digits, 0011 1010
The Opcode is basic machine instruction like ADD, SUBTRACT, LOAD, STORE and the operand is the value or location of the value to be operated on.
All arithmetic is carried out in the register.
60
High level code
High level codes typical instructions look like math or english and are easy to guess or understand the meaning. Python, Delphi and Java are known as high level codes
High level languages have complex statements and program structures can not easily be translated into machine code. Each statement in high level code represent several machine code statements
61
Assembly language
Going from machine to assembly code was very time consuming, and is sometimes called a "first generation language".
Assembly is the "second generation" eg.
LDA 1 Mark1 ; Load contents of Location17 into Register 1
62
Instruction Set in terms of processor handling
Processors vary in the number and type of instructions they can process.
They cannot deal with WHILE, THEN etc.
Compare and Branch instructions are used test conditions and jump to another if true
63
Assembler
A computer can not process assembly language instructions directly
The assembler is a program which translates assembly code into machine language
64
Compiler
A program the translates high level language program (source code) into machine code
A compiler translates every statement in the program into machine code, called object code.
If the compiler hits a syntax error it will not translate the statement and no code is produced
65
Interpreter
A type of program which translates high level program into machine code
It works by translating line by line. It translates one line and if it has no syntax errors it executes it it moves on to the next line.
66
Compiler vs. Interpreter
Compiler:
- Has to correct all syntax errors before running
- Fast execution of object code
- Once object code is produced it can be run and
installed on any computers
- A user can not see source code after purchase
Interpreter:
- Good for program development as parts of the program
can be executed despite having errors
- Slow execution as every line must be translated before
execution
- A user must have the programming language and
interpreter on their computer
- A user can make changes and sell your program after
purchase
67
Advantages and Uses of Assembly code
Advantages:
- Manipulation of individual bits and bytes
- Runs very fast
- Occupies less memory than code compiled from a high
level language
Uses:
- Hardware specific code like driver devices telling the
computer how to communicate with eg. boot code in
ROM, printer, scanner etc.
- Control programs in embedded systems in washing
machines, modems, routers, cars, digital watches etc.
- Real time applications requiring instant response,
network software, medical equipment
68
Importance of data
Millions of organisations keep data about their customers, members and products.
Banks, governments, health departments, shops, schools and and exam boards all keep data on computers
69
Some threats to data
Accidental damage:
- Data entry errors
- Program errors
- Errors in procedure
- Accidental loss or deletion
- Hardware failure, damage or crash
Natural disaster:
- Fires, floods etc.
Malicious actions
70
Backups and archives
Backups are made regularly so lost or corrupt data can be restored.
Backups should be stored in a secure location offsite. Employees taking home a backup tape or mirroring all transactions on a second remote computer.
Archived data is data that is no longer needed for immediate processing but needs to be kept
71
Cloud storage
Holding all company data in "the cloud" is becoming more and more popular and considered safer than data stored in an office.
72
Physical security
Data needs to be kept physically safe from intruders, in large companies by...
Issuing staff with ID
Having all visitors sign in on arrival and having escorts around the office
Keeping sensitive areas locked
Security cameras
Security guards
73
Physical Security and Biometrics
```
Locks on doors
Security Guards
Biometrics:
- Fingerprint recognition
- Retina scanner
- Iris recognition
- Voice recognition
```
74
Audit trails and logs
Audit trail maintains a record of all activity on a computer system
The time and date a user accesses the system will be logged as well as their activity
Assists in detecting security violations
Help system admin ensure the system has not been harmed by hackers, insiders or technical problems
75
Acceptable use policies (AUP)
Many businesses and educational facilities require employees or students to sign an AUP before being given a network ID
76
Secure passwords
Minimum of 8 characters
Mixture of numbers, lowercase and uppercase characters
Include symbols
Do not include name, DOB or personal details
77
Phishing
A phishing email is one that tricks you into handing over your personal or sensitive information
You receive an email leading you to a bogus site to enter your details from where they are captured by phishers
What to look out for:
Generalised impersonal greeting
Sender's address, variation from original
Forged link, roll mouse over link to check
Request personal information, legit sites do not do this
Sense of urgency
Poor spelling and grammar
78
Pharming attacks
Similar to phishing but instead of using a fake link in email, pharming redirects victims to bogus sites despite entering the legit website
Detecting pharming attacks:
ISPs filter out bogus redirects as soon as an attack is detected
Check the URL once loaded has not changed
Before entering sensitive information check that http has changed to https
79
Trojan Horse Email
Offers something tempting to look at like an attachment or link eg. funny video
When you open the attachment or click the link it installs a virus on your computer which may:
- record your keystrokes and send them to the attacker
- Provide someone else with access to your files
- Use your computer to send spam to everyone in your
address book
80
Virus generated emails
Appear to be sent from a friend
Usually means your friend's email has been infected and sent to their entire address book
Typically includes product or shop recommendation and asks for emergency cash
Encourages you to click a link to a sales website or transfer cash
81
Encryption
Encryption is the encoding of data so that it can no longer be easily understood to safeguard the data if intercepted.
Terminology:
Plaintext: original message
Ciphertext: encrypted message
Encryption: the process of converting plaintext into ciphertext
Key: a sequence of numbers used to encrypt or decrypt, often data using a mathematical formula.
Encryption algorithm: the formula for encrypting the plaintext
Encryption techniques:
Private key (symmetric encryption)
A single key used to encrypt and decrypt a message and must be given to the recipient of your message to decrypt the data
Public key (asymmetric encryption)
Two keys are used, one to encrypt and one to decrypt
This is more secure as you never have to send or reveal your decryption key
82
Caesar shift cipher
Earliest known substitution cipher invented by Julius Caesar
Each letter is replaced by n positions further in the alphabet
n is the key used to encrypt and decrypt the message - symmetric encryption
83
Cryptanalysis
The objective of cryptanalysis is to decode the ciphertext - typically by finding the secret key
Methods include:
Brute-force attack
every possible key is tried
Non-brute-force attack (cryptanalysis)
84
Key strength
5 bits would enable 2^5 key combinations so it could be said that you are using 5 bit encryption
Increasing the number of bits used for a key increases encryption strength.
85
Algorithmic security
Ciphers are based on computational security
keys determined using computer algorithm
given enough computer power and time any key can be cracked.
86
Strong and weak encryption
Encryption can be considered "strong" when the useful lifetime of the encrypted data is less than the time needed to crack it
Weak encryption means that the encryption can be cracked while the encrypted data is still in its lifetime
87
Other methods of data protection
Passwords
SSL (security protocol)
TSL (security protocol)
Firewalls
HTTPS
88
Proxy server
A proxy server is a computer that acts as an intermediary between a web browser and the internet.
It helps to improve web performance by storing a copy of frequently accessed web pages.
A proxy server may act as a firewall
can help to improve security by filtering out some web content like malware
responds to input packets by blocking and allowing some
gateway from one network to another
89
HTTPS
s in https stands for secure
| this means a security protocol is used to ensure a trusted encrypted data connection
90
Secure Sockets Layer and Transport layer security
SSL is a protocol for transferring private documents via the internet
it uses asymmetric encryption to encrypt data before transmission
many websites use SSL to receive confidential information like credit card details
TSL is a more recent upgrade to SSL. Like SSL it uses public key to encrypt.
91
Process of getting web page from webserver
Web browser sends request to IP address or web server to identify itself by providing certificate
Web page sent from web server to browser
Browser renders HTML to display web pages
HTTPS used to secure data
92
Benefits of USB connection
```
Universal connection
High transmission speeds
No incorrect connections
Can be inserted both ways
Backwards compatible
Fast data transfer speed
Inexpensive to purchase
```
93
Protocols to transfer data safely
HTTPS
SSL
TSL - layers are handshake and record
Computer Science IGCSE
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