Little Computer 3

This repository contains a simple implementation of the Little Computer 3. With its simple instruction set the VM is fairly straight-forward and the code speaks for itself.

There's a few examples of assembly projects in the /asm/ folder.

Hello World

.ORIG x3000                         ; Address of the first instruction
HELLO_STR .STRINGZ "Hello, World!"  ; Define "Hello, World!" string
LEA R0, HELLO_STR                   ; Load address of HELLO_STR to R0
PUTs                                ; Print R0 to STDOUT
HALT                                ; Halt program
.END

To actually run the code, it has to be built into an .obj file. Those are included in the /obj/ folder.

TODO

• Better keyboard I/O

The VM doesn't automatically send the keyboard input from the syscall, it waits for the user to press enter.

• Logging

This section needs the biggest improvement. The only thing that should go into STDOUT is the actual print syscalls made by the programs. Everything else should be a debug log only available under a special flag.

Run

Clone the repository

> git clone https://github.com/hum/lc3-vm
> cd lc3-vm

Build the binary

# or "make run" for the hello world example
> make build

Run the programs from /obj/

> ./bin/lc3_vm ./obj/2048.obj

LC3 Tools

If you wish to convert your own .asm files into .obj files then you can do so by downloading the codebase from here.

> cd lc3tools
> ./configure --installdir /path/to/loc/
> make
> make install

Now you will have ./lc3as in your /path/to/loc/ which you can use to generate the .obj files

Resources

• Justin Meiners' blog
• Instructure Set Document
• This project doc by BYU