comp sci mindmap

comp sci mindmap

1. Binary

   • Arithmetic overflow
     • When there are insufficient bits to store the result from addition due to a final carry bit.
   • Binary shift
     • left shift multiplies by 2
     • right shift divides by 2
   • Check digit
     • A calculation on data to create a number included with the data for error checking
     • When the number is input the check digit is recalculated to check it matches
     • Therefore valid data can be assumed

2. Units

   • Bit
     • binary digit 0 or 1
   • Nibble
     • 4 bits
     • Half a byte
   • Byte
     • Can represent 1 character in ASCII
     • 8 bits
   • Kilobyte (KB)
     • 1024 bits
     • ~1000 bytes
   • Megabyte (MB)
     • 1024 KB
     • ~1,000,000 bytes
   • Gigabyte (GB)
     • 1024 megabytes
     • ~1,000,000,00 bytes
   • Terabyte (TB)
     • 1024 gigabytes
     • ~1,000,000,000,00 bytes
   • Petabyte (PB)
     • 1024 gigabytes
     • ~1,000,000,000,000,000

3. 1.1.1 architecture of cpu

   • Von Neumann architecture
     • a system where cpu runs programs stored in memory
     • programs consist of instructions and data which are stored in memory adress
     • made of CU, ALU, MDR and MAR
   • cpu architecture
     • CPU
       • brain of the computer
       • processes all data and instructions
       • power of cpu is dependent on various things
     • 3 main parts
       • CU (control unit)
         • Controls the cpu Main job is to manage the fetching, decoding and execution of program instructions by following the fetch-execute cycle controls the flow of data inside the cpu (to alu, registers, cache) and outside the cpu (to main memory and input/output devices)
         • did in notes
       • ALU
         • does all calculations
         • completes simple addition and subtraction, compares the size of numbers and can do multiplications and divisions
         • performs logic operations and binary shifts
         • it contains the accumulator register
       • cache
         • very fast memory
         • slower then registers
         • faster then ram
         • low capacity, expensive
         • stores regularly used data so the cpu can access it quickly
         • different levels depending on speed and storage

4. Protocols and layers, wireless and wired

   • Common protocols
     • A protocol is a set of rules that allows two devices to communicate
     • TCP/IP
       • Communication over a LAN/WAN
       • Provides error-free transmission between two routers
     • HTTP[S]
       • Web page requests
       • A client-server method of requesting and delivering HTML web pages
       • Encryption and authentication for requesting and delivering HTML web pages. Used to transfer sensitive information – e.g., passwords, bank details
     • FTP
       • File transfers
       • Used to send files between computers, typically via a wide area network
     • POP
       • Retrieves email from a mail server, removing it from the server and transferring it to your device
     • IMAP
       • Email
       • Used by mail clients to manage remote mailboxes and retrieve email from a mail server.
     • SMTP
       • Sends email to an email server
     • IP
       • Routes packets across a wide area network. Along with TCP, it makes up the TCP/IP protocol stack.
   • Modes of connection
     • Wireless
       • Wifi
         • 100m range
         • High bandwidth
         • High power consumption
         • Convenient
         • Slower then wired
         • Doesn't constrict user
       • Bluetooth
         • 10m range
         • Low bandwidth
         • Low power consumption
         • Ideal for connecting headphones or mics
     • Wired
       • Fiber optic
       • Ethernet
         • Used for communicating on a wired local area network
         • Provides reliable, error-free, fast communication between two points
         • User location is limited by the need for a physical cable connection
         • An Ethernet setup relies on lots of cables, connections, ports and physical hardware, raising costs
         • Reliable
       • Copper

5. Algorithms

   • Computational thinking
     • Decomposition
       • break one large, complex problem down
       • create sub problems
       • work out each sub problem
     • Algorithmic thinking
       • logical way of getting a solution
       • allows solutions to be reused
     • Abstraction
       • keep important info
       • remove that which is not needed
       • simplification
   • Designing coding and refining
     • Flowcharts
       • line shows direction of algorithm
       • rhombus is input or output
       • rectangle is process
       • diamond is decision
       • oval is terminal (start/end)
     • Pseudocode
       • back of y11 book