The requirement that a computing system should run continuously and persistently has never been explicitly taken into account as an essential and/or general requirement by traditional system design and development methodologies. As a result, a traditional computing system ofien has to stop its running and functioning when it needs to be maintained, upgraded, or reconfigured, it has some trouble, or it is attacked. This paper presents the author's vision of persistent computing, a new methodology and/or paradigm that aims to develop continuously dependable and dynamically adaptive reactive-systems, called "Persistent Computing Systems". The paper presents what is a persistent computing system and why we should study persistent computing systems as continuously available, reliable, and secure systems, discusses how persistent computing systems can be constructed by soft system bus technology to satisfy their requirements, and shows some new scientific and technical chdlenges on persistent computing.