Dale Skrien

CPU Sim 3.1: A tool for simulating computer architectures for computer organization classes

CPU Sim 3.1 is an educational software package written in Java foruse in CS3 courses. CPU Sim provides students an active learningenvironment in which they can design, modify, and compare variouscomputer architectures at the register-transfer level and higher.They can run assembly language or machine language programs forthose architectures through simulation. CPU Sim is a completedevelopment environment, including dialog boxes for designing theCPU architecture, a text editor for editing assembly languageprograms, an assembler, several display windows for viewing theregisters and RAMs during the execution of programs, and manydebugging features such as the ability to step forward or backwardduring execution, inspecting and optionally changing the values inthe registers and RAMs after each step. These features andsuggested uses of CPU Sim in CS3 classes are discussed.

Chronological orderings of interval graphs

Abstract If an undirected graph is the intersection graph of a set of intervals of the real line, it is called an interval graph and the set of intervals is called an interval representation of the graph. An interval graph typically has many representations that differ in the order of the endpoints of the intervals along the line. This paper gives three methods for describing these differences and shows how these methods can be used to determine whether a graph has a representation satisfying various restrictions on the relative positions of the intervals. It concludes with an application of these results to the subject of interval counts of interval graphs.

Expertiza: students helping to write an OOD text

Students in a masters-level object-oriented design class participated in several exercises related to improving a not-yet-published textbook in object-oriented design. Each student was asked, sometime during the semester, to improve an explanation from the book, to make up an example of a concept described in the book, and to create an exercise for a chapter in the book. Their contributions were peer-reviewed by other members of the class. A strong majority of the students (29 of 49) indicated that they learned a lot from doing the assignments, and 27 of 49 of them agreed or strongly agreed that the assignments were enjoyable-a good measure of their engagement. The textbook author found the feedback very helpful in revising the textbook.

A multilevel simulator at the register transfer level for use in an introductory machine organization class

Abstrac! This paper discusses simulator and its use in the new simulator is presented a multilevel classroom. A that allows the user to dynamically change the simulated hardware at run time. We also discuss an incremental series of projects that we have successfully used with the simulator. These projects give the student hands-on experience with the advantages and disadvantages of several architectures.

Homogeneously representable interval graphs

Abstract We characterize those interval graphs G with the property that, for every vertex v , there exists an interval representation of G in which the interval representing v is the left-most (or right-most) interval in the representation.

IASSim: a programmable emulator for the princeton IAS/Von Neumann machine

In this paper, we describe a programmable emulator for the Princeton IAS/Von Neumann machine. The emulator is historically accurate, preserving the quirks and eccentricities of the machine. It is also user-friendly and robust, suitable for undergraduate architecture and programming classes as a teaching tool. Users can write non-trivial programs in IAS assembly code or machine code. We present some examples here, and discuss assignments from its first use in two undergraduate classes. IASSim is a Java application publicly available at no cost.

Learning Appreciation for Design Patterns by Doing it the Hard Way First

People who have to live without something often have a greater appreciation for what that thing can do for them than those who have never experienced life without it. In particular, a software designer can have a greater appreciation for what design patterns can contribute to software development if he or she has first had some experience developing software without the use of such patterns. An object-oriented design course is discussed in which students were given a sequence of projects in which they needed to design and implement their solutions before the appropriate patterns were introduced. Then after the patterns were discussed, the students were told to refactor their code using these patterns. The positive and negative aspects of this approach to teaching design patterns are discussed.

Debugging on the Shoulders of Giants: Von Neumann's Programs 65 Years Later

A study that examined and executed the programs John von Neumann wrote for the IAS machine reveals time-tested truths about computer architecture, side effects, instruction set design, and automatic programming-truths all foreseen by von Neumann and his team more than 50 years ago.