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Edexcel GCSE Computer Science - Coggle Diagram
Edexcel GCSE Computer Science
Software
Operating Sytems
Purpose
Enables hardware to communicate with software
Provides an interface for users to interact with (GUI)
Provides platform for other software to run on
Functions
File Managment
Organises and keeps track of files stored on the secondary storage
OS splits new files into smaller pieces and records the start location of the file and sequence number
Copy, save, open, delete, rename, ect.
Process Management
The OS uses a scheduling algorithm to control processes
Queue
Executes each program in order
Round Robin
Each process is given a limited amount of CPU time. Once it has used its time, it is sent to the back of the queue
Memory Allocation
Virtual memory can be created on the secondary storage
OS uses a
paging algorithm
to swap processes between the RAM and the virtual memory
Peripheral Management
The OS manages communication between hardware and software
Each peripheral has its own device driver - software that relays instructions and data between the OS and the peripheral
User Management
The OS provides and runs the user interface, which can be graphical or command-line
Access Control
Authentication - password, fingerprint, face recognition, ect.
User privileges (e.g. read only)
Utility Software
Disk Defragmenter
On HDD, moves files to be in continuous line, to make it faster to read
Compression
Encryption
Encrypts data and allows decryption with a password
Data Backup
Number Bases
Programming Languages
High Level
Python, C, C++, Java, Javascript, ext.
Easier for humans to read, write and understand
Opposite of low level pros/cons
Low Level
Individually addresses hardware components of the device
Machine code, Assembly
Difficult to read, write and understand for humans
Basic high level instructions can take many lines of low level code
Architecture specific
May run faster as it can be optimised
Translators
Interpreter
Translates each line one at a time
Only have to maintain the source code
Slower to run, but no time taken to compile
Interpreter must be installed
Compiler
Creates an executable file when ran, in machine code
Faster whilst running, but time needed to compile
Provides a single report of all syntax errors after compiling
Safer for developers, as risks IP to send off source code
Different compiler needed for different architecture
Translates source code into machine code, to be read and executed by the computer
How Computers Work
Data
Networks
Network Security
Data should be:
Confidential
Correct
Available
Vulnerability Testing
Penetration Testing
Done with the permission of the organisation
Black-Box
Tester acts as an outsider, without inside knowledge or authorisation
White-Box
Acts as an insider with authorisation and inside knowledge
All unauthorised hacking is illegal whether or not harm is done.
White-hat hackers "ethically" hack, not causing harm
Black-hat hackers cause harm
Methods to secure networks
Encrypt data
Install firewalls
Physical security (guards, cameras, ext.)
Internet
A collection of networks connected together by routers
A router connects two or more networks together and forwards data packets
Receives a data packet
Read the destination IP address
Uses its routing table to forward the data packet to its next step on the shortest possible route
Data Packets
Packet/Sequence Number
Destination IP address
Source IP address
Number of packets
Checksum
TCP/IP Stack
Application Layer
Email Protocols
POP3 : Downloads from server and then deletes
IMAP : Downloads email but retains on server
HTTP/HTTPS
Transfer of webpages
FTP : File transfer protocol
Transport Layer
TCP
Responsibke for splitting data into packets
Generates checksum, sequence numbers and packet header
Checks data is correct and if not requests packets
Internet Layer
Internet Protocol (IP)
Adds the source + destination to the packet header
IPv4 and IPv6
Link Layer
Converting digital data to physical transmission
Ethernet, WiFi, ext.
Artificial Intelligence
Algorithm that can recognise patterns and make predictions
Algorithmic Bias
AI draws conclusions that are not intended
Due to biased data inputted, as well as small data sets
Issues
Privacy
Can know a lot about you
Data collection from websites such as Instagram
Social
Can take jobs, although can also create them
Legal
Who is held accountable?
Incorrect medical diagnosis
Moral
Cybersecurity
Malware
Virus
: embeds in host file, needs to be executed
Worm
: Standalone code, can replicate and spread independently
Trojan
: appear to be a valid piece of software but contain malware
Ransomware
: encrypts data and demands money for decryption key
Keylogger
: Logs all key inputs, often used to steal passwords
Social Engineering
Phishing
: illegitimate websites/messages pretending to be legitimate -> often contain spelling errors or sense of urgency, and won't address you by your name
Blagging / Pretexting
: Usually by phone, someone will pretend to be a company to get credentials
Quid Pro Quo
: Pretending to be helping someone, only to install malware
Protection
Antimalware
Inspects a file for recognised malware
Software patches
Internet
Python Programming
Text Files
Read
with open(FILENAME, 'r') as theFile:
for line in theFile:
line = line.strip().split(',')
list.append(line)
Write
with open(FILENAME, 'w'/'a') as theFile:
for record in list: