A visual simulator has been developed as an example of Web-based education tool, which is designed for students to understand graphically internal behavior and structure of computer system in a course of information engineering education. It is written in Java programming language, downloadable from Web server and executable on almost types of personal computer including Java virtual machine and major Web browsers. Our visual simulator can demonstrate how computer works, for example, instruction fetching, instruction decoding and executing in the register-transfer level. In order to utilize our simulator as an effective tool for distance education, it is necessary to improve its availability which can show some kinds of sample programs and on-line help guide from Web server and let users exchange information about visual simulator with teacher and/or friend by means of mail service. Especially, our simulator can efficiently provide communication service between users through the invoc...