lc3_vm 0.1.0

LC-3 (Little Computer 3) VM implemented in Rust. Ideally, it will run any LC-3 assembly program.
Documentation 
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use super::sign_extend;
use crate::hardware::register::condition_flag;
use crate::hardware::register::Registers;
use crate::hardware::Memory;

/// An address is computed by sign-extending bits [8:0] to 16 bits and adding this value to the incremented PC.
/// The contents of memory at this address are loaded into DR.
/// The condition codes are set, based on whether the value loaded is negative, zero, or positive.
pub fn ld(instr: u16, registers: &mut Registers, memory: &mut Memory) {
    let dr = (instr >> 9) & 0x7;
    let pc_offset = sign_extend(instr & 0x1ff, 9);
    let val: u32 = pc_offset as u32 + registers.r_pc as u32;
    registers.update(dr, memory.read(val as u16));
    condition_flag::update_r_cond_register(dr, registers);
}