Computer science UNIT ONE (NOT COMPLETED)
- Created by: NeveHughes
- Created on: 22-03-19 11:52
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- UNIT ONE
- Computational thinking
- Abstraction
- Removing unnecessary detail
- Decomposition
- Breaking large problems into smaller key problems which are easier to solve
- Computational thinking
- Using computers to solve problems
- Algorithmic thinking
- Using clear logic and algorithms (list of instructions) to solve problems
- Abstraction
- CPU (Central Processing Unit)
- Clock Speed
- Controls the number of cycles that can be run per second
- Cores
- The more cores the faster the processing speed
- Cache
- The more caches the faster the processing speed
- Two levels of cache
- Level One is very small, fast and expensive memory but located on the CPU
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- Two levels of cache
- The more caches the faster the processing speed
- Embedded Systems
- Dumb programs
- Found in washing machines, Alarm clocks, Ovens , Dishwashers
- Microprocessor
- Componants
- MAR (Memory address register)
- Holds the instructions for the data being fetched
- MDR (memory data register)
- Holds the data being fetched
- Acumulator
- Where the results of the ALU are stored
- ALU (Arithmetic logic unit)
- Performs all arithmetic and logic calculations
- Program counter
- Every time an instruction or piece of data is collected the PC increases by one
- Cache
- RAM - stored on the processor making it closer to the CPU meaning that the memory is faster to access increasing the Processor speed
- MAR (Memory address register)
- Fetch- decode - execute cycle
- Clock Speed
- Memory
- RAM (Random Access Memory)
- Volatile
- ROM (Read Only Memory)
- Non-Volatile
- Loads the BIOS
- Basic Input Output System
- Loads the instructions to run the hardware
- Virtual
- Extends the memory and prevents the computer from crashing
- Flash
- RAM (Random Access Memory)
- Storage
- Types of storage:Magnetic: Mechanical parts move over the disks surface to read and write data magnetically Optical: Lasers read and write data using light Solid State: Data is recorded onto solid memory chips without any moving parts
- Magnetic
- Basic Features
- Disk containsconcentric circlescalled tracks
- Each track is dividedinto sectors
- Disk heads mountedon mechanical armsread and write the data
- Advantages and Disadvantages
- Cheap, vast storage capability, fast write speed
- Lots of mechanical parts, durability an issue, sealed unit dueto disk head and platter precision and not very portable
- Uses
- Personal computers, storage of vast quantities of data
- Capacity
- 500GB - 6TB or greater
- Basic Features
- Optical
- Basic Features
- Data is stored as pits andlands burnt into a spiraltrack circulating outwardsfrom the centre
- From this signal, 0s and 1scan be derived fromreflections or no reflections
- Capacity
- CD-ROM – up to 720MbDVD – up to 8.4GbBlu-Ray – up to 50Gb
- Advantages and Disadvantages
- Cheap, very easily portable, takes up little space physically
- Less storage capacity compared to other typesEasily damaged / scratched, requires a CD readerSlow write speeds
- Uses
- Songs, videos and other multi-media storage, backup andarchiving of data
- Basic Features
- Solid State Drives (SSD)
- Basic Features
- Solid-state disks usenon-volatile flash memory tostore information
- Very fast burst read/writespeeds due to data beingphysically close and easy torecover
- No mechanical or movingparts
- How it works
- Large electric current used to force electrons through a barrier and trap them on the other side. They remain on the other side until “flashed” with anew current, hence the name
- Solid State Drives (SSD)
- Basic Features
- Solid-state disks usenon-volatile flash memory tostore information
- Very fast burst read/writespeeds due to data beingphysically close and easy torecover
- No mechanical or movingparts
- How it works
- Large electric current used to force electrons through a barrier and trap them on the other side. They remain on the other side until “flashed” with anew current, hence the name
- Large electric current used to force electrons through a barrier and trap them on the other side. They remain on the other side until “flashed” with anew current, hence the name
- Advantages and disadvantages
- Highly durable, no moving parts, very fast read/write speeds,no noisy fan, faster start up times
- Expensive at present, less storage capacity / physical sizethan traditional hard disks
- Uses
- Portable computers,Military usage
- Basic Features
- Solid State Drives (SSD)
- Large electric current used to force electrons through a barrier and trap them on the other side. They remain on the other side until “flashed” with anew current, hence the name
- Advantages and disadvantages
- Highly durable, no moving parts, very fast read/write speeds,no noisy fan, faster start up times
- Expensive at present, less storage capacity / physical sizethan traditional hard disks
- Uses
- Portable computers,Military usage
- Basic Features
- Magnetic
- Flash memoery
- Advantages: Low cost, portable, no moving parts, durable
- Uses
- Cameras, Mobile phones, USB memory sticks
- Types of storage:Magnetic: Mechanical parts move over the disks surface to read and write data magnetically Optical: Lasers read and write data using light Solid State: Data is recorded onto solid memory chips without any moving parts
- Networks
- Local Area Networks (LAN'S)
- A LAN operates on a single site such as a school orsmall business using their own cabling systems
- Advantages: Sharing resources such as printers saves money,You can access your files fromany computer in the network, Data is easy to back up as it isstored centrally on the server
- Disadvantages:Purchasing the networkhardware is expensive, Managing a large network iscomplicated, Viruses may be able to infiltratethe network and infect everycomputer
- Wide Area Networks (WAN)
- A WAN uses cables, telephone lines, satellites andradio waves to connect, usually spread over a widegeographical area
- Topologies
- Star
- Advantages: Fast data transfer as there arefewer data collisions, If one cable fails the otherworkstations are not affected
- Disadvantages:Requires additional hardwaresuch as the central switch, If the central device fails thewhole network goes down
- Mesh
- Advantages No single point of failure – It is aself-healing network, Expansion and modification canbe done without disrupting thenetwork, Data can be transmitted fromdifferent devices simultaneously
- Disadvantages:Can involve redundantconnections, Expensive to install cabling ifusing wired connections, Network maintenance andadministration is difficult
- Star
- Network hardware
- A Network Interface Card (NIC) in your computer or device
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- Router: Sends data packets on their way in the best direction
- Switch: Central, multi-plug adapter for computers and printers in a network :When a packet of data is received, it broadcasts the packet to all devices on the network
- Switch: Smart multi-plug adapter only sends packets to the intended recipient, using its MAC address: Reduces network traffic and increases speed
- A Network Interface Card (NIC) in your computer or device
- Ethernet protocols
- ‘Ethernet’ refers to a family of standard localnetworking ‘protocols’ or rules
- It describes how devices should format data readyfor transmission between computers on the samenetwork
- Local Area Networks (LAN'S)
- Computational thinking
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