Computers

Key Terms

• Input/Output Subsystem – allows the computer to interact with the environment
  • Converts physical input into binary information
  • Converts binary information into physical output
• Central Processing Unit – brains of the computer
  • Processes the binary information and calls programs
  • Fetches instructions from memory and executes them
• Programs – predefined instructions that the CPU accesses
  • Acts on the binary information
• Memory – where programs are stored
  • Stores the binary information
• Bit – the smallest piece of information a computer can store (on/off)
• Operating System – the program that manages how the software uses the hardware of a computer
• Compiler – translates source code (human-readable) into machine code
  • First: turns source code into tokens or words (Lexical Analysis)
  • Second: tokens are organized in a hierarchical order known as a parse tree (Syntactic Analysis)
  • Third: compiler denotes the context of the code (Semantic Analysis)
  • Fourth: browse through the parse tree and find machine code that does the same thing as the source code

Key Actions

• Receive input
• Store information
• Process information
• Produce output

Circuits

• Input/Output are just information that can be stored as on/off electrical signals (1s and 0s)
• Circuits modify and process information that’s inputted as ones and zeros
  • And, Not, Or, Nand, Nor, Xor
• Smaller circuits mean less travel distance for electrical signals, leading to faster processing speed
  • Electricity moves at just about the speed of light

Binary

• Numbers: each digit represents 2n instead of 10n. Ex. 1001 = (1×8) + (0x4) + (0x2) + (1×1) = 9
• Text: each letter is assigned a number which is represented with a binary number, which is represented by a sequence of wires that turn on/off
• Images: each pixel is represented by numbers to show color, each number is represented in binary, and thus wires
• Sound: every sound is just a vibration that can be represented by a waveform graph. Each point on the graph can be represented by a number, therefore each sound can be represented as a sequence of numbers. Higher quality audio just means taking more points in the graph