Swing LMC: Little Man Computer with Interactive Features

A Java Swing implementation of the Little Man Computer (LMC), a popular tool for teaching computer architecture.

First developed in 2007

Copyright (C) 2007 - Andrew Kwok-Fai Lui

The Open University of Hong Kong

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, see http://www.gnu.org/licenses/.

Introduction

The LMC is a popular tool for teaching computer architecture created by Dr. Stuart Madnick in 1965. Refer to the Wikipedia page Little Man Computer for the details.

Installation and Execution

Pre-requisites

• Java JDK or JRE 1.8 or above

Instruction

1. Download the repository to a folder, assuming that it is /app/SwingLMC. The Java sources are in the src folder and the classes are found in the bin folder.
2. Execute SwingLMC.class insider the folder

cd /app/SwingLMC

java -cp "./bin" SwingLMC

Screenshot

Notes:

• The editor pane on the left allows LMC program editing. You may also load a program file, and save the edited program as a file.
• The memory pane is on the top-left. It will be filled with data after you Assemble the code (under the Tool menu item on the menubar). The memory pane can be edited.
• The process status pane shows the registers.
• The memory pane will highlight the current execution address. Select Execute Slowly to see it more clearly.

Extension to the LMC

The Assembler supports logical address labeling. An address label, which is a single uppercase letter, may be defined for arbitrary addressing. The following program shows the use of label B.

The purpose is to ease programming effort of students during development. After testing the program, the students may be asked to convert it to real addresses.

00  IN      ; input first number
01  STO 97  ; store first number
02  IN      ; input second number
03  STO 98  ; store second number
04  SUB 97
05  BRP B   ; 98 > 97
06  LDA 97   ; 97 > 98 so swap 97 and 98
07  STO 96
08  LDA 98
09  STO 97
10  LDA 96
11  STO 98
B : LDA 97
    OUT
    LDA 98
    OUT
    HLT