GCSE Computer science theory
- Created by: GladyGartland
- Created on: 01-03-18 16:10
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- Computer science theory
- Programming languages
- Machine code
- A low level language that only computers understand
- Displayed in binary
- A low level language that only computers understand
- High level languages
- Uses English and mathematical symbols - humans are able to understand this language
- Binary
- The only language computers understand
- Binary can be used to represent all data types on a computer e.g. Images, Sound
- Binary addition rules
- 0+0=0
- 1+0=1
- 1+1=0 carry 1
- 1+1+1= 1 Carry the 1
- Binary addition rules
- Binary to Hexadecimal
- 1. Split the bits it to two sets of 4
- 2. Add in the column headings
- 3. Merge the output and find the corresponding hexadecimal value
- Data conversions
- 8 bits in a byte
- Kilobyte = 1024 bytes
- Gigabyte = 1024 MB
- Megabyte = 1024 KB
- Terabyte = 1024 GB
- Data compression
- Lossy
- The file is compressed and some data is permanently lost along with some of the quality
- Lossless
- The file is compressed but the quality remains the same, the original file can be brought back if desired
- Lossy
- Encryption
- Data is more secure
- Those who are meant to read a message can because they have the 'Key'
- Data is more secure
- ASCII
- Character representation
- Each character has a decimal/ deanery value which has a binary value
- Character representation
- Machine code
- The internet
- The internet
- A global network any computer can join
- Data is sent and received when you...
- Visit a web page
- Send an email
- Data is sent and received when you...
- A WAN - Wide Area Network
- IP addresses help computers find each other like a post code
- With out an IP address information would never end up where it is needed
- A global network any computer can join
- Protocols
- A set of rules agreed about the internet
- Protocol layers
- Application
- Provides access to email files and websites across an IP network
- FTP, HTTP, POP, IMAP, SMTP
- Provides access to email files and websites across an IP network
- Transport
- Devides massages into packets
- TCP, UDP
- Devides massages into packets
- Internet
- Manages the addresses of sources and finds their destinations
- IP
- Manages the addresses of sources and finds their destinations
- Link
- Transmits and receives data through cables
- ETHERNET, Wi-Fi
- Transmits and receives data through cables
- Application
- Topologies
- Bus
- All work stations are connected and joined to one cable (The bus)
- Ring
- Signals travel around the ring in one direction and each device receives each packet
- Each device is connected two other devices
- Star
- Each individual device is attached to a central point
- Data is sent to the device which put in the request
- Bus
- Networks
- A group of computers and other devices connected together
- How is information protected??
- Encryption
- Firewalls
- Passwords
- Network Security
- Protects data from threats
- Keeps information confidential
- Ensures data remains in the right hands
- The internet
- Programming languages
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