1. A task management system using a single processor to manage tasks, said task management system comprising: a first data block retaining information on scheduling of the managed tasks which is included in information on arbitrary tasks; a second data block retaining information which is not recorded in said first data block; and a third data block for selecting the highest priority task from among executable tasks; wherein: information on one task is divisionally managed by said first data block and said second data block; said first data block is used as a data block to be inserted into or deleted from said third data block; and when priority inheritance from one task to another task is performed, only the correspondence between said first data block and said second data block is changed.