Sampling
Recording a signal at regular intervals
Sampling frequency
Num of samples obtained per second
Greater sampling frequency means
Better quality but bigger file size
Sample size
How many bits are available for each sample - bit depth
Bit rate formula
Sample frequency x bit depth
File size formula
sample frequency x bit depth x time
Lossy compression
Some data is removed from the file
Lossless compression
Rearranged data to make it more efficient
RLE - compress 'yyyybbbpppprr' where y is yellow b is blue etc
4y3b4p2r
NOT gate
Reverses input
OR gate
Returns true if either / both input are true
AND gate
Returns true if both inputs are true
XOR gate
Returns true if either (not both) are true
Application software
Used to carry out tasks on a computer e.g web browsers
System software
Peforms tasks need to operate the hardware e.g operating system, utility software
Operatig system
Manages computer system e.g linux
Machine code (low level)
Binary
Assembly code (low level)
Communicates with computer
High level code
Like Python
High level vs Low level
programmer understands vs computer understands
Translators and why their needed
Converts code from one language to another - all code needs to be translated to machine code
Assembler
Converts assembly to machine code
Compiler
Converts high level to machine code translates the whole block
Interpreter
Converts high level to machine code translates line by line and slower than compiler
ALU
Perform arithmetic and logic operations
Control Unit
Coordinates the CPU
Register
Quick small stores of data in cpu
Clock
Provide signals to synchronise internal components
RAM is (non volatile / volatile)
Volatile memory that can be read/write to
ROM is (non volatile / volatile)
Non volatile memory that can only be read to
Cache
Fast but small memory that stores frequently used data
Cores
Processing units
Optical storage
Binary data
Light is shined and light that hits a land reflects differently to when it hits a pit. E.g pits can be read as 0 and lands as 1. Data is written with a laser burning the pits into the disk
Optical 1 disadvantage 2 advantage
Small capacity
Reliable
Very portable
Magnetic storage
Parts of the surface are either magnetised (1) or demagnetised (0) by the electromagnets in the head.
Magnetic 1 disadvantage 2 advantage
Can be noisy and generate heat
Large capacity
Cheap
Solid State Storage
Form of flash memory
SSD 1 disadvantage 2 advantage
Expensive
Silent
Reliable as non-mechanical
Embedded system
A special purpose computer
Network
Connection between devices to share resources
Protocols
Set of rules for communication
Application layer protocols
HTTP/S, FTP, SMTP, IMAP
Transport layer protocols
TCP, UDP
Internet layer protocols
IP
Link layer protocols
Ethernet, Wifi
Application layer
Where the network applications operate
Transport layer
Sets up communication between two hosts
Internet layer
Handles and routes data
Link layer
Where hardware operates
Viruses
Insert themselves in normal programs
Adware
Generates unwanted adverts
Trojans
Disguised as a desirable software but there is malware hidden within it
Spyware
Collects data about the user
Blagging
Inventing a scenario to gain a victim trust
Phishing
Obtaining private info through a fake link often pretending to be something your not
Pharming
Cyberattack where websites traffic is redirected to a fake site
Shouldering
Viewing private info over the person shoulder
Firewalls
Monitor network traffic and filter packets based on rules
White box penetration test
Attempting to gain access with some knowledge and basic credentials - simulating an inside attack
Black box penetration test
Attempting to gain access with no knowledge - simulating an outside attack
HTTPS use
used for accessing webpages from a server and uses encryption to secure data
SMTP VS IMAP
handling out bound email vs handling in bound email
TCP VS UDP 1 similarity and 3 differences each
Similarity; exists to deal with connection between devices
Differences; TCP - two way connection splits and slower and more reliable
UDP - sends data one way and faster and less reliable
IP protocol use
Enables communication over the internet
2 enviromental issues of computing
too much energy use and finite resource use
2 cultural issues of computing
changing the job market and social media also makes it easier to spread abuse and hold politicians accountable
2 ethical issues of computing
the right to privacy conflicting with the government ensuring public safety e. g FBI asking apple to hack into a phone
2 legal issues of computing
Blackmail , stealing of financial info