Posts Tagged "NodeJS"

Over the past couple of months, apart from writing my book, “You Suck at Programming” ¹, I’ve been working on an emulator/interpreter for the famous computer simulation “Little Man Computer", by Peter Higginson. It was created many years ago to help students learn about how the CPU and memory worked and interacted with each other, and was a great way for me to try and understand some lower level emulation, as it has an instruction set consisting of just nine operations. These operations are:

ADD – Addition
SUB – Subtraction
DAT – Data Storage
LDA – Load Data
STA – Store Data
HLT – Halt Program
BIZ – Branch if Zero
BRA – Branch Always
BZP – Branch if Zero or Positive

They all sounded fairly simple to implement, so I went about creating the first prototypes for the interpreter of this program. Initially, I tried to create a dictionary with 99 data spaces to store my data, however this ended up causing a lot of problems for me down the line. I eventually had to scrap the entire idea, and ended up just using a simple two dimensional array. Now that that was sorted, I needed to somehow get a standard data format including data and addresses, and have an interpreter read them properly. Luckily, Little Man Computer is close enough to a real computer that it uses “opcodes”, small (in this case 3 character) strings which tell you which command is being executed, and at what address. So, the format I came up with looked like this: