1. A processing system comprising: software for processing a plurality of data items representing the smallest logically meaningful data unit, said software being formed of a plurality of software components and a control program responsive to high level events corresponding to an occurrence of a particular state in a data item; input/output means for accepting input and displaying output data, said input/output means creating low level events, dependant upon a particular hardware upon which said input/output means resides, in response to input by an operator; storage means for storing the plurality of software components, each software component being related to a particular data item processed by said software, each software component being activated in response to a corresponding event; control means activated in response to an occurrence of an event, specifying a software component to be executed in response to the event; processing means for executing the specified software component subsequent to the corresponding event, said processing means transferring the result of executing the selected software component to said input/output means as output data; and said control means including: a first table representing a relationship between an event and a software component corresponding to the event; a second table representing a relationship between a first software component and a second software component to be executed after a completion of execution of the first software component; and event conversion means that converts the low level events created by said input/output means to a high level event such that the high level event does not depend upon the content of an event created by said input/output means or upon the particular hardware upon which said input/output means resides whereby the software components may be utilized without direct dependance upon low level events.