4.Each ACOS task is the smallest thread of execution which can compete on its own for system resources ,it may exist in one of the folio whig five states: executing, ready, blocked,dormant,non-existent .
8.In this paper,we analyze the interrelations between the return rate of the securities port- folio and its system risk,in view of the lim itation of the Markowitz Model and CAPM,we found a portfolio investment decision model with rebuilt constraint on risk,which is more feasible in prac- tice.
