Computional thinking

Computional thinking

1. System Architecture

   • Clock Speed
     • How many instructions a CPU can fetch decode and execute in a second.
     • This is how fast a CPU can run, this is measured in mega or giga hertz (MHz or GHz)
     • Has a limit to how fast the clockspeed can go.
       • This can be changed to go faster, which is called overclocking
         • Going to fast can corrupt files.
   • Cache Size
     • Holds temporary intructions and data that is likely to be used again.
     • Takes less time to get the instuctiond from the RAM to the CPU.
     • More cache=more data stored next to the CPU, making the comuter faster.
     • Chache is more expensive than RAM.
   • Number of Cores
     • A processing unit containing ALU, control units and registers.
     • More cores=more power to run multiple programs.
     • Channels between cores take up some of the speed.
   • ALU
     • Used for calculations and logical comparisons.
       • Arithmetic: 2+1=3 Logical: 2>1
     • Every task done by the computer requires calculations which require the ALU
   • Embedded Stystems
     • A computer system within a computer system
       • An example of this would be a washing machine

2. Memory

   • The purpose of RAM
     • Holds temporary data and applications that are deleated as soon as power is disconnected
     • Can be changed by a program or user and is a volitile storage.
   • The purpose of ROM
     • Can’t be changed by any program or user.
     • Holds the startup instructions as a lack of power doesn’t change what the ROM can ratain.
     • This is non-volitile storage.
   • Virtual memory
     • This is stored in the secondary storage, on the hard drive when the RAM is full.
       • This is becuase the hard drive is slower because of how far it is from the CPU. The hard drive is also the only available space.
   • Flash memory
     • Non-volitile. This is used as portible electronics and removable storage is it doesn’t lose the data when it has no power.

3. Storage

   • Secondary storage
     • Is the non-volitile
   • Optical
     • Stored on a disk. This is read by a lazer. It is portable but can break easily.
   • Solid state
     • Non-volitile storage that stores and recieves information with electonic circuits.
   • Key differences
   • Magnetic storage
     • Used for backup of important files from the hard disk

4. Wired and Wireless Networks

5. Network Topology

   • Topology
     • Ring Topology
       • Each device is connected by a wire to each other device. This creates a ring.
         • The data will travel quickly as it goes in one directoon, no matter how many devices, the data won't crash
         • Disadvantages are that if the main cable breaks or is faulty the whole network will fail
     • Star Topology
     • Bus Topology
       • All devices are joined by one cable (the bus). At the end of the cable, two terminators, one for each side, will stop signals reflecting back down the bus.
         • Advantages
           • Easy to install
         • Disadvantages
           • If the main cable fails or is faulty, the whole network will break
           • As more nodes are added, the more the network slows.
           • Every node can see all the data on the network, this is a security risk
   • IP addresses
   • Layers
   • Wifi Frequencies
     • Frequency of 2.4 GHz and 5 GHz
     • 14 channels
   • Packet Switching
   • Protocols
     • Ethernet
     • Wifi
     • TCP
     • IP
     • HTTP
     • HTTPS
     • SMTP
     • IMAP
     • FTP
     • UDP