CS 33211 Operating Systems
Project #1
Due via e-mail by 11:59pm on Wednesday, October 13, 2004
Objective
This project should be done individually. In this project you will read the Nachos source code and answer
questions about it. You will also modify Nachos code to implement the programming assignment. The
project is worth the total of 50 points.
Getting Started
First, you have to install and compile Nachos. See the instructions on the course’s webpage. After
successful compilation of Nachos, run the executable to make sure it produces the expected results.
Reading Nachos Source Code
It is suggested that you read the files in the order described below. As you do so, read the corresponding
sections in Thomas Narten’s “A Road Map Through Nachos” and Archna Kalra’s “Salsa – An Operating
Systems Tutorial”. The links to both of these documents are available from the course’s webpage.
First, read the code for Nachos operating system. It is located in subdirectory threads. When you
compiled Nachos the Makefile turned THREADS directive on (there are several pointers to makefile
tutorials on the webpage for the course). Notice what portions of code in the files below were included due
to this directive. Note also that other Nachos features like USER_PROGRAM, FILESYS, and NETWORK
were turned off. Notice what command line arguments you can give to Nachos and what global data
structures are created. Start reading the code by going through the following files
• threads/main.cc, threads/threadtest.cc – main function and simple test of thread
routines;
• threads/system.h, threads/system.cc – Nachos startup/shutdown routines;
Read through the following files to see how Nachos implements and schedules threads. Study the
Scheduler and Thread classes:
• threads/thread.h, threads/thread.cc – thread data structures and thread operations
such as fork(), yield(), sleep(), and finish();
• threads/scheduler.h, threads/scheduler.cc – manages the list of threads that are
ready to run;
• threads/switch.h, threads/switch.s – assembly language routines for creating, and
deleting threads and context switch. Skim through these files. You are not expected to understand the
details.
• threads/list.h, threads./list.cc – generic list management
• threads/utility.h, threads/utility.cc – some useful definitions and debugging
routines.
After reviewing Nachos OS part, look at the Nachos simulated machine. The code for the machine is
located in machine directory. Concentrate on the files listed below:
• machine/machine.h, machine/machine.cc – emulates the part of the machine that
executes user programs: main memroy, processsor regiester, etc.;
• machine/mipssim.cc – emulates the integer instruction set of a MIPS R2/3000 CPU.
• machine/interrupt.h, machine/interrupt.cc – manage enabling and disabling
interrupts as part of the machine emulation;
• machine/timer.h, machine/timer.cc – emulate a clock that periodically causes an
interrupt to occur;
