COMP 40
Machine Structure and Assembly-Language Programming
Tufts University
Fall 2009

What's this class about and why am I taking it?

• Machine structure shows how data is represented at the machine level.
• Assembly language is how code is represented at the machine level.

• The construction of very high-level abstractions and programming languages on top of very low-level hardware is one of the great intellectual achievements of computer science, and every computer scientist should know about it.
• The data and code model of any particular machine, called its instruction-set architecture, represents a contractual agreement between hardware designers and systems programmers that allows a collection of programs to run on any hardware which conforms to the instruction-set architecture. The exploitation of instruction-set architecture to enable both hardware and software to be changed independently and reused with each other is one of the great engineering achievements of computer science, and every computer scientist should know about it.
  (Some of the fruits of this exploitation include operating systems that will run on any x86-compliant hardware; the ability to buy new, more advanced CPUs without having to replace your software; and the ability to create and use ``virtualization environments'' such as VMware, QEMU, Xen, and so on.)
• A programmer may understand a high-level program's outputs and interactions by understanding only the model of computation presented by the programming language. But to understand how a program performs, one needs a working knowledge of computation at the machine level.
• When something goes wrong in a software system, diagnosing the fault often requires the ability to break the abstraction barriers presented by programming languages and to inspect the state and behavior of the machine at its own level, not the level of programs' source code.
• Much software that is critical to the world's computing infrastructure is written in the languages C and C++, and to understand how this ``systems software'' works, one must understand machine-level computation.

• You will be able to understand and improve the real performance of programs written in high-level languages.
• You will be able to diagnose and fix bugs that can't be explained without appealing to the underlying machine model. Many important bugs in C and C++ programs fall into this class.
• You will have started learning how to exploit the underlying hardware in ways that are not possible using high-level languages alone.

Which books do I really, really need?

If you're willing to teach yourself C through the web, you can survive without Kernighan and Ritchie. However, it is one of the best computing books ever written, and it will serve you well for years.

The "main text" by Bryant and O'Hallaron is actually not a great fit for the course, and it's not the sort of thing you're likely to use a lot afterward. But there are a few topics, like caches and assembly code, which may be quite hard to understand without some sort of book. If you need to save money, this is the place to do it—you can always try the library or try to borrow a friend's copy.

How can I find out more?

Course admin and course materials

• Sketch of course Syllabus and Schedule
• Lecture notes I prepare for class
• Homework Assignments and solutions.
• Lab handouts
• Grading standards
• Other details for which you are responsible
  • Prerequisites
  • Policies and procedures (homework, etc.), including what sorts of collaboration are permissible.
  • Computer software and accounts for the course
• Handouts for in-class exercises
• Code that you may find helpful for labs or homework

Technical information

• Idioms for C programmers
• Design checklists:
  For a single abstraction
  For a whole program
• C Interfaces and Implementations Quick Reference
• How to connect to linux.cs.tufts.edu using VNC
• Highlighted handouts and advice:
  • A Short Guide to Working With Unix Libraries—all about compiling and linking.
  • Pair programming: What to do when you're not holding the keyboard
• Dinkumware's documentation for the Standard C Library and C99 library overview.
• Useful links to AMD64 information
• Readings
• Search for answers on Stackoverflow:
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