For the introduction of computer architecture in computer science, highly simplified specification of CPU, and visualization of CPU operation are important. This paper describes a CPU simulator we have developed. It supports students' learning of introduction of computer architecture. It presents internal status of CPU by processor block diagrams, and provides buttons for manipulation in various ways. And our simulator provides set of the diagram and the buttons as the progress of students' learning.

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SUMMARYThe string analysis is a static analysis of dynamically generated strings in a target program, which is applied to check well-formed string construction in web applications. The string analysis constructs a finite state automaton that approximates a set of possible strings generated for a particular string variable at a program location at runtime. A drawback in the string analysis is imprecision in the analysis result, leading to false positives in the well-formedness checkers. To address the imprecision, this paper proposes an improvement technique of the string analysis to make it perform more precise analysis with respect to input validation in web applications. This paper presents the improvement by annotations representing screening of a set of possible strings, and empirical evaluation with experiments of the improved analyzer on real-world web applications. key words: static string analysis, input validation, web applications