Nostalgic Pickled Mango

    little-man-computer

    1.0.1 • Public • Published

    Little Man Computer

    Little Man Computer emulator in Node.

    Specifications

    assemble

    assemble is a function which takes in a string of newline-delimited Mnemonic, or Numeric, instructions, with or without labels, and outputs an array of numeric instructions.

    commands

    commands is an enum mapping each mnemonic to it's command code. For example, ADD is mapped to 100

    Computer

    Computer is a constructor that is used to create a Little Man Computer. This constructor takes an options argument defined below.

    options

    • inbox An array with the inputs for the program. If this array doesn't exist or is too small when the computer requires an input, the program will thrown an error.
    • mailboxes An array with the numeric codes that make up the program.
    • logOutbox Boolean value specifying whether or not to log outputs as they happen to console.log. Defaults to false

    The methods and attributes in the Computer object are defined below

    run()

    This method runs the computer until it reaches a halt statement.

    step(steps=1)

    This method runs the computer the specified number of steps, and then pauses.

    outbox

    This property is an Array consisting of the outputs of the program.

    accumulator

    This is a number which represents the current state of the accumulator.

    programCounter

    This is a number which identifies the next mailbox index to be evaluated for a command. When paused using step, this will point to the next instruction to be run.

    inboxIndex

    This is the index of the next inbox instruction to be retrieved.

    Usage Example

    const LMC = require('little-man-computer');
    //This program takes a user input and counts down to zero
    const countdown = `     INP
         OUT      // Initialize output
    LOOP BRZ QUIT // If the accumulator value is 0, jump to the memory address labeled QUIT
         SUB ONE  // Label this memory address as LOOP, The instruction will then subtract the value stored at address ONE from the accumulator
         OUT
         BRA LOOP // Jump (unconditionally) to the memory address labeled LOOP
    QUIT HLT      // Label this memory address as QUIT
    ONE  DAT 1    // Store the value 1 in this memory address, and label it ONE (variable declaration)`;
    const assembledCode = LMC.assemble(countdown);
    const computer = new LMC.Computer({
      inbox: [5],
      mailboxes: assembledCode,
      logOutput: false
    });
    computer.run();
    console.log(computer.output); //[5, 4, 3, 2, 1, 0]
    

    Caveats

    BRZ Negative Flag

    Does not branch if accumulator's negative flag is set (accumulator is -1).

    Overflow on ADD

    The result will be -1.

    Underflow on SUB

    The result will be -1.

    Install

    npm i little-man-computer

    DownloadsWeekly Downloads

    4

    Version

    1.0.1

    License

    ISC

    Last publish

    Collaborators

    • cakenggt