GCSE Computing
- Created by: Riya.b123
- Created on: 21-02-19 13:36
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- The CPU
- Registers
- Buses
- Cache
- Arithmetic Logic Unit
- Clock
- Control unit
- decoder
- Control Unit
- Coordinates actions of computer
- Sends control signals to other parts of CPU & components of computer
- Decoder works out what program instructions mean
- Registers
- Accumulator - stores calculation results
- Program Counter - holds address of next instruction to be fetched
- Memory Data Register - Temporary store for anything copied from memory
- Memory Address Register - holds address of memory location currently being read or written to
- Cache Memory
- very fast memory
- speeds up processing by storing recently or frequently used instructions
- As it becomes larger it takes longer to find data so becomes slower
- Too expensive to use for main memory (RAM) in personal computers
- Multi-Core Processors
- contains more than one CPU
- give fast processing speeds
- Can work on different tasks at the same time
- Embedded Systems
- Components on single printed circuit board - processor, memory
- Built for small range of specific tasks
- General purpose
- Washing machine, digital camera, microwave etc.
- RAM & ROM
- Random Access Memory - computer stores data & instructions when application is running
- Data can be read & written
- Volatile - data lost when power off
- Often removable
- Read Only Memory - stores instructions that don't need to be changed during normal use
- Data can be read
- Non volatile - retains data if power off
- Random Access Memory - computer stores data & instructions when application is running
- Virtual Memory
- slow
- Disc Thrashing
- Data Swapping
- Magnetic Storage
- used in hard disc drives & digital tapes
- Data encoded on surface
- Low cost
- Large capacity
- Fast
- Not portable
- Durable & Reliable
- Optical
- CDs, DVDs, Blue-ray
- use laser to read & write data
- Low capacity
- slow
- Cheap
- portable
- reliable but not durable
- Solid State
- Made of flash memory
- SSDs, SD cards, USBs
- Moderate capacity
- Very fast
- more expensive than magnetic & optical
- portable
- reliable
- LAN
- a network in a small geographical area
- manged by local manager or team at site
- home or school
- WAN
- connects several LANs over large geographical area
- Large companies
- communicate with computers & users in other locations
- managed by several people or parts of an organisation
- Factors affecting network performance
- Bandwidth
- Hardware & Software limitations
- A high number of users
- High network traffic
- Client Server Network
- users log in to access programs & data stored on them
- servers responsible for security
- all files backed up centrally
- Peer To Peer Network
- no server to manage network
- each client acts as server
- security is distributed
- data stored on each client
- user responsible for backup
- The Internet
- WAN
- web hosting
- IP addresses
- Domain Name Service
- Topologies
- Star - each computer connected to a central hub or switch
- if one fails all the others would work
- easy to add new devices
- a lot of cables
- Mesh - each computer connected to all other computers
- if one fails there is an alternative route
- expensive
- Star - each computer connected to a central hub or switch
- Protocols
- TCP/IP - allows computers to communicate across a WAN
- FTP - transfer files
- HTTP & HTTPS
- SMTP - emails
- POP - retrieve emails
- IMAP - emails read & stored on server
- Packet Switching
- data split into small sections
- packets inspected
- Packets arrived to user
- may not be in order
- Threats to networks
- Phishing - emails claiming to be from banks etc.
- Blagging - criminal persuading victim to give personal info
- Shouldering - finding pins by watching
- weak passwords
- Malware
- virus - program hidden inside another - spread
- worm - replicate & send emails
- Trojans - delete files
- Spyware & Adware
- Brute force attakcs, data interception & theft, DOS, SQL
- Phishing - emails claiming to be from banks etc.
- Prevention of vulnerabilities
- Penetration testing
- network forensics
- anti malware software
- encryption
- firewalls
- Operating system
- manages user interactions through user interface
- manages peripheral devices
- user interface
- Graphical user interface
- utility software
- encryption software
- data compression
- defragmentation
- application software
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