\section{Design Principles}
\label{sec:designprinciples}
-The Pintos series of projects are built on a number of principles.
+Pintos's projects are built on a number of principles.
-\paragraph{Read before You code.}
+\paragraph{Read before you Code}
Each project involves a significant amount of reading code before
-students write the first line of their code.
+students write the first line of code.
Because software maintenance constitutes the vast majority of all
-software development efforts~\cite{askEliforcite}, this setup mirrors the
+software development efforts~\cite{Boehm1981Software}, this setup mirrors the
environment in which most software engineers work.
+Simultaneously, we limit the amount students have to read
+by encapsulating lower layers, such as device drivers.
We went to great lengths to write the entire Pintos baseline code,
-and in particular the portions students will read, in a style that shows,
-by example, the coding style we expect from students. This style
-includes purely syntactical convention such as the choice of the
-GNU indentation style, and extends to commenting style and naming
-conventions. During the semesters in which Pintos was used, we
-continuously refined the internal code documentation, focusing on those
-portions that initially proved difficult to understand or confusing.
+and in particular the portions students must read, in a style that shows,
+by example, the coding style we expect from students.
+% cut for length
+%This style includes purely syntactical convention such as the choice of the
+%GNU indentation style, and extends to commenting style and naming conventions.
+We continuously refined the internal code documentation over several
+semesters, focusing on those portions that initially proved difficult to understand.
\paragraph{Maximize Creative Freedom}
OS design involves a tremendous amount of creative freedom, both in the
-choice of algorithm and data structures. Our projects are designed to
+choice of algorithms and data structures. Our projects are designed to
stimulate creativity by avoiding the prescription of specific approaches
-to accomplish each project's goals. Instead, students must design their
+to accomplish each project's goals. Instead, students design their
own data structures and associated algorithms as much as possible.
\paragraph{Practice Test-driven Development}
%Test-driven development~\cite{Edwards}
-Each project includes a large number of test cases that is accessible
-to students. In keeping with us adopting an internal perspective, students
-do not develop test cases, rather, they must implement the API that is exercised
-by these test cases.
+Each project includes a large number of test cases that are accessible
+to students, as shown in Table~\ref{table:tests}.
+They must implement the API that is exercised by these test cases.
+Students are encouraged to add their own test cases.
\paragraph{Work in a Team}
The projects presented in this paper are designed to be accomplished by teams of
2-4 students. Working in a team provides an environment that more closely resembles
-industrial software development, and it provides a way for students brainstorm and
+industrial software development, and it provides a way for students to brainstorm and
implement together. In addition, we teach and require the use of group collaboration tools,
notably shared source code version control systems such as CVS.
\paragraph{Justify your Design}
Design justification and rationale is as important for learning as creating an artifact
-that fulfill a set of given requirements. We designed a set of structured questionnaires
+that fulfills a set of given requirements. We designed a set of structured questionnaires
in which students describe their design and discuss choices and trade-offs they made.
-\paragraph{Provide a reproducible, manageable environment.}
-Some concurrent environments are difficult to manage and debug.
+\paragraph{Provide a Reproducible, Manageable Environment}
+Operating Systems are inherently concurrent environments, which can be difficult
+to debug. For educational use, we must provide an environment that is
+manageable and reproducible, which we do by providing the option
+of running Pintos in a simulated, fully deterministic environment.
+As a result, Pintos kernels can be debugged in a manner that
+is substantially similar to how user programs are being debugged.
-Teaching OS involves teaching concurrency
+\paragraph{Include Analysis Tools}
+Dynamic analysis tools are now being widely used in software development;
+an OS course should be no exception.
+In Section~\ref{sec:dynamicanalysis}, we describe how we
+extended the QEMU emulator~\cite{Bellard2005QEMU} to
+perform tailored analyses that find errors such as race conditions.
-Operating systems are fundamentally
+\paragraph{Provide Extensive and Structured Documentation}
+If using an instructional system requires too much undocumented knowledge,
+the system is often not shared or falls into disuse because the learning curve
+for instructors is too steep and training teaching assistants is difficult.
+Pintos includes an extensive 129 page manual, a sample solution,
+and grading instructions for teaching assistants. The project documentation
+highlights sections students must read from sections that merely provide supplemental information.
+%Even though Pintos uses an existing and complex architecture, our experience indicates
+%that the manual is sufficient for most students.
-\paragraph{Provide analysis tools.}
projects / pintos-anon / blobdiff