MOSS Memory Management Simulator
Installation on Unix/Linux/Solaris/HP-UX Systems


This document provides instructions for the installation of the MOSS Memory Management Simulator on Unix operating systems. This procedure should be the same or similar on Unix, Linux, Solaris, HP-UX and other Unix-compatible systems. The MOSS software is designed for use with Andrew S. Tanenbaum, Modern Operating Systems, 2nd Edition (Prentice Hall, 2001). The Memory Management Simulator was written by Alex Reeder ( This installation guide was written by Ray Ontko (

This installation guide only provides information about installing the software and testing the configuration for Unix-like operating systems. To install on Windows operating systems, please read the Installation Guide for Win95/98/Me/NT/2000 Systems. For more detailed information about the simulator, please read the User Guide.


The following software components are required to install and use the MOSS Memory Management Simulator.


Before installation, you should verify:

If you're using a standard command-line java compiler, the following instructions will help determine if your environment is configured correctly.

  1. Verify that you have java installed and configured in your environment.
    $ java -version
    You should see a message like this with possibly a different version number.
    java version "1.1.8"
    If you get a message like:
    java: Command not found.
    Then java may not be installed on your system, or may not be configured for your use.

    If you think that Java may already be installed on your system but may not be in your "path", you can find it by

    $ find /usr -name java -print
    On my system, for example, the following is returned.
    On my system, I also searched for "javac" and found that it exists in /usr/bin/java. I'll use this jdk for my installation.

    If Java isn't available on your system, you should check with your instructor or system administrator. If you administer your own system, then you should be able to find a copy of Java for your operating system.

    If you find that java is installed but not configured for your use, then perhaps you need to add it to your path. Consult your instructor or system administrator if you need help adding this to your path.

  2. Verify that the java compiler is installed and configured in your environment.
    $ javac
    If you're using a standard java command-line compiler, you should see a message similar to this.
    use: javac [-g][-O][-debug][-depend][-nowarn][-verbose][-classpath path][-nowrite][-deprecation][-d dir][-J]
    If you get a message like:
    javac: Command not found.
    then the java compiler may not be installed on your system, or may not be configured for your use. Consult your instructor or system administrator.

  3. Verify that that the current directory is in your classpath.
    $ echo $CLASSPATH
    You should see a list of directories separated by colons (":") or possibly just a blank line. If you don't see the directory "." (a single period, which stands for the current directory), then you should add it to the claspath.

    Determine which shell you're using:

    $ echo $SHELL

    If you're using sh, ksh, or bash:

    $ export CLASSPATH

    If you're using csh, or tcsh:


If you have a working java runtime environment, a working java compiler, and the current directory is in your path, then you're ready to proceed with the installation.


Installation of the software can be accomplished with these simple steps:
  1. Create a directory in which you wish to install the simulator (e.g., "moss/memory").
    $ cd
    $ mkdir moss
    $ cd moss
    $ mkdir memory
    $ cd memory

  2. Download the compressed tar archive (memory.tgz) into the directory. The latest release for this file can always be found at

  3. Expand the compressed tar archive.
    $ tar -xzf memory.tgz
    $ gunzip memory.tgz
    $ tar xf memory.tar


The directory should now contain the following files:

Files Description
memory.tgz Compressed tar archive which contains all the other files.
Java source files (*.java)
Compiled Java class files (*.class)
commands Sample input command file
memory.conf Sample configuration file
Documentation and associated images
copying.txt Gnu General Public License: Terms and Conditions for Copying, Distribution, and Modification


The distribution includes compiled class files as well as the source java files. You should not need to recompile unless you decide to change the code. If you wish to compile the code, the following commands should work if you're using a Java compiler that accepts the normal "javac" command line.

$ javac -nowarn *.java
The -nowarn flag supresses warning messges, of which there may be several. For backward compatability we use only those features of Java which have been present from the beginning, some of which are deprecated and are usually reported by the compiler with warning messages.


To test the program, enter the following command line.

$ java MemoryManagement commands memory.conf

The program will display a window allowing you to run the simulator. When the window presents itself, click on the Run button. You should see the program "execute" 7 memory operations, about one per second. When the simulation completes, click the Exit button.

The memory operation commands are read from a file called "commands", and the initial configuration and various options are specified in the file "memory.conf". The program also produces a log file called "tracefile" in the working directory.

The "commands" file looks something like this:

// Enter READ/WRITE commands into this file
// READ <OPTIONAL number type: bin/hex/oct> <virtual memory address or random>
// WRITE <OPTIONAL number type: bin/hex/oct> <virtual memory address or random>
READ bin 100
WRITE hex CC32
READ bin 10000000000000000
READ bin 10000000000000000
WRITE bin 11000000000000001
WRITE random

If things are working correctly, the "tracefile" should look something like this:

READ 4 ... okay
READ 13 ... okay
WRITE 3acc32 ... okay
READ 10000000 ... okay
READ 10000000 ... okay
WRITE c0001000 ... page fault
WRITE 1ff82cdc ... okay

The program and its input and output files are described more fully in the MOSS Memory Management Simulator User Guide.

© Copyright 2001, Prentice-Hall, Inc. This program is free software; it is distributed under the terms of the Gnu General Public License. See copying.txt, included with this distribution.

Please send suggestions, corrections, and comments to Ray Ontko (

Last updated: July 28, 2001